Fix JOC detection inside mp4/mkv containers

.github/workflows/build.yml

@@ -1,12 +1,14 @@
 name: build
 
-# Builds both architectures and publishes the two installable component packages.
+# Builds both architectures, publishes the two installable component packages as
+# workflow artifacts, and — when a tag is pushed — turns them into a GitHub release.
 # The SDK is fetched from foobar2000.org at build time (tools/setup_sdk.ps1) and the
 # renderer sources are part of this repository (kernel/), so nothing else is needed.
 
 on:
   push:
     branches: [ main, master ]
+    tags: [ 'v*' ]
   pull_request:
   workflow_dispatch:
 
@@ -20,6 +22,16 @@ jobs:
         shell: pwsh
         run: ./tools/setup_sdk.ps1 -TargetVersion 80
 
+      - name: Check the tag against the component version
+        if: startsWith(github.ref, 'refs/tags/')
+        shell: pwsh
+        run: |
+          $declared = (Select-String -Path src/main.cpp -Pattern '#define JOC_VERSION "([^"]+)"').Matches[0].Groups[1].Value
+          $tag = '${{ github.ref_name }}'
+          if ($tag -ne "v$declared") {
+            throw "the tag $tag does not match JOC_VERSION $declared; the release would be mislabelled"
+          }
+
       - name: Build both architectures and package them
         shell: pwsh
         run: ./tools/package.ps1
@@ -41,3 +53,28 @@ jobs:
           name: foo_input_joc-x64
           path: dist/*-x64.fb2k-component
           if-no-files-found: error
+
+  release:
+    # A pushed tag is what makes a release; branch builds only leave artifacts.
+    if: startsWith(github.ref, 'refs/tags/')
+    needs: windows
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Collect the packaged components
+        uses: actions/download-artifact@v4
+        with:
+          path: dist
+          merge-multiple: true
+
+      - name: List what will be published
+        run: ls -l dist
+
+      - name: Create the release for this tag
+        uses: softprops/action-gh-release@v2
+        with:
+          name: ${{ github.ref_name }}
+          files: dist/*.fb2k-component
+          fail_on_unmatched_files: true
+          generate_release_notes: true

README.md

@@ -9,16 +9,26 @@ install beside `foo_input_joc.dll`.
 
 ## What it does
 
-1. Reads the E-AC-3 syncframes and decides from the bitstream whether the file really
-   carries JOC (an EMDF container holding both the OAMD and the JOC payload).
-2. A file without JOC is handed back to foobar2000 with `exception_io_unsupported_format`,
-   so the built-in E-AC-3 decoder plays it — this component never decodes plain E-AC-3.
-3. A JOC file is decoded as: the syncframes go to the renderer as metadata, the 5.1 core
+1. Finds the audio: a bare `.eac3` / `.ec3` stream is read as it is, while a container
+   (`.mp4`, `.m4a`, `.m4b`, `.m4p`, `.m4r`, `.mov`, `.mkv`, `.mka`, `.webm`) is looked into
+   first — the container's own headers say whether an E-AC-3 track is present and which
+   audio track it is (MP4 sample entry `ec-3`, Matroska `CodecID A_EAC3`), and ffmpeg then
+   copies that track out of the file byte for byte. The header walk is bounded and cheap, so
+   an MP4 holding AAC is declined without starting anything.
+2. Decides from the bitstream whether it really carries JOC (an EMDF container holding both
+   the OAMD and the JOC payload — container metadata only ever says "E-AC-3", and the JOC
+   flag inside it is frequently missing).
+3. A file with no E-AC-3 track, or with one that carries no JOC, is handed back to
+   foobar2000 with `exception_io_unsupported_format`, so the built-in decoder plays it — this
+   component never decodes plain AC-3 or E-AC-3.
+4. A JOC file is decoded as: the syncframes go to the renderer as metadata, the 5.1 core
    PCM comes from ffmpeg, and the renderer pairs them (one syncframe : 1536 bed samples)
    and produces the output PCM, which is handed back to foobar2000.
 
 ```
-.eac3 file
+.eac3 / .ec3 file          container (.mp4 .mkv .m4a ...)
+  │                          ├─ header walk (src/container_scan.cpp) ── no E-AC-3 ──▶ next decoder
+  │                          └─ E-AC-3 track ── ffmpeg -c:a copy ──▶ syncframes
   ├─ JOC check (src/eac3_scan.cpp)  ─── no JOC ──▶ built-in E-AC-3 decoder
   └─ JOC
       ├─ syncframes ────────────────────▶ renderer metadata
@@ -34,12 +44,13 @@ install beside `foo_input_joc.dll`.
 |---|---|
 | `kernel/` | Copy of the `joc_core` C++ sources (`include/` + `src/`) and `joc_kernel.vcxproj`, the static library the component links |
 | `src/eac3_scan.*` | Syncframe walk and the JOC bitstream test |
+| `src/container_scan.*` | Bounded header walk of MP4/MOV and Matroska: is there an E-AC-3 track, which one, and how long is the file |
 | `src/joc_decode.*` | Decode engine: starts ffmpeg, drives the renderer, handles the end of stream. No foobar2000 headers, so it also builds into the offline tools |
 | `src/input_joc.cpp` | The foobar2000 input: format recognition, yielding, `get_info`, `initialize`, `run` |
 | `src/settings.*` | Configuration values and their environment overrides (development only) |
 | `src/prefs.cpp`, `src/prefs.rc` | The preferences page |
 | `src/log.*` | Diagnostic log written next to the DLL |
-| `tests/` | Offline tools: bitstream self-test and cross-check against the renderer, render harness, preferences-page layout check |
+| `tests/` | Offline tools: bitstream self-test and cross-check against the renderer, render harness, preferences-page layout check, container-probe check |
 | `tools/` | SDK fetch, build, package, deploy, unattended test bed run |
 
 ## Build
@@ -70,6 +81,21 @@ Always let foobar2000 exit through `/exit`; a force-killed instance leaves a
 `<profile>\running` marker behind and the next start then refuses to load any user
 component.
 
+### Containers need one look at the decoder list
+
+foobar2000 tries the decoders in the order shown in Preferences → **Decoding** (the
+"list of available decoders", where entries can be moved up and down). The built-in
+container readers are in that list too, and when one of them is offered an MP4 or Matroska
+file before this component, it takes the file and the JOC objects are lost — the file plays
+as plain E-AC-3.
+
+So, to play JOC from a container, move **JOC decoder (E-AC-3 JOC)** above **foobar2000 MP4
+Demuxer** and **foobar2000 Matroska/WebM Reader** in that list. Nothing else is needed, and
+bare `.eac3` / `.ec3` files are unaffected by the order. This is the same thing every
+third-party decoder (the FFmpeg wrapper, for one) asks for, which is why the component does
+not try to work around it. If a container still plays as plain E-AC-3, that list is where to
+look.
+
 ## Settings
 
 Preferences → Tools → **JOC decoder**:
@@ -101,7 +127,10 @@ Development only: they override the stored settings for one run and every use is
 ## Known limitations
 
 * ADM BWF output is not implemented.
-* Containers (`.m4a`, `.mkv`) are not claimed: only bare `.eac3` / `.ec3` streams.
+* A container is only claimed when this component is ahead of the built-in container reader
+  in Preferences → Decoding, as described under [Install](#install); the core does not let a
+  decoder ask for a file another entry has already taken.
+* Transport streams (`.ts`, `.m2ts`) are not claimed.
 * The room tail is returned in full; the reference command-line renderer additionally trims
   trailing samples below a threshold, so its output can be shorter.
 * x86 and x64 do not produce bit-identical binaural output (last-bit differences): the

VERIFICATION.md

@@ -113,3 +113,22 @@ disabled, which is what "the option is there but cannot be clicked" otherwise lo
 
 Not verified here: how the page and the `%joc_*%` fields look on screen; that needs a human
 in front of the window.
+
+## Container support (mp4 / m4a / mov / mkv / mka / webm)
+
+Verified with the Win32 build, a 5.1 speaker layout, and the component installed in a
+portable foobar2000 1.6.19 profile:
+
+- `ffmpeg -i <bare .eac3> -c:a copy` muxed into MP4 and Matroska, then `-map 0:a:0 -c:a copy
+  -f eac3` extracted again, is byte-identical to a direct `-t 30 -c:a copy` of the source
+  (same SHA-256) — the renderer therefore sees the stored syncframes, not a re-encode.
+- The header probe (`tests/container_scan_test.cpp`, no foobar2000 involved) reports, for the
+  same material: `joc.mp4 -> mp4 eac3=1 audio#0 codec=ec-3 30.016 s`,
+  `joc.mkv -> matroska eac3=1 audio#0 codec=A_EAC3 30.016 s`, `plain_eac3.mp4 -> ec-3`,
+  `ac3.mp4 -> ac-3 (declined)`, `aac.mp4 -> mp4a (declined)`.
+- End to end, with the component ordered ahead of the container reader in
+  Preferences -> Decoding: `open()` is called, the track is found, the JOC verdict is positive,
+  the file is claimed, and playback reaches `end of stream`.
+- Negative case end to end: an MP4 holding E-AC-3 without JOC yields with
+  `E-AC-3 track 0 carries no JOC`, and the built-in decoder plays it.
+- Bare `.eac3` / `.ec3` handling is unchanged.

foo_input_joc.vcxproj

@@ -95,6 +95,7 @@
   </ItemDefinitionGroup>
 
   <ItemGroup>
+    <ClCompile Include="src\container_scan.cpp" />
     <ClCompile Include="src\eac3_scan.cpp" />
     <ClCompile Include="src\input_joc.cpp" />
     <ClCompile Include="src\joc_decode.cpp" />
@@ -105,6 +106,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <ClInclude Include="src\container_scan.h" />
     <ClInclude Include="src\eac3_scan.h" />
     <ClInclude Include="src\joc_decode.h" />
     <ClInclude Include="src\joc_pch.h" />

src/container_scan.cpp

@@ -0,0 +1,528 @@
+#include "container_scan.h"
+
+#include <windows.h>
+
+#include <cstdarg>
+#include <cstdio>
+#include <cstring>
+#include <vector>
+
+#include "log.h"
+
+namespace joc_container {
+namespace {
+
+std::wstring utf8_to_wide(const std::string& text) {
+    if (text.empty()) return {};
+    const int needed = MultiByteToWideChar(CP_UTF8, 0, text.c_str(),
+                                           static_cast<int>(text.size()), nullptr, 0);
+    std::wstring out(static_cast<std::size_t>(needed), L'\0');
+    MultiByteToWideChar(CP_UTF8, 0, text.c_str(), static_cast<int>(text.size()), out.data(),
+                        needed);
+    return out;
+}
+
+// A bounded, read-only view of the file.  Every accessor returns false instead of
+// throwing, so a truncated or hostile file simply fails the probe.
+class Window {
+public:
+    bool open(const std::string& path) {
+        const std::wstring wide = utf8_to_wide(path);
+        handle_ = CreateFileW(wide.c_str(), GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
+                              nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+        if (handle_ == INVALID_HANDLE_VALUE) {
+            handle_ = nullptr;
+            return false;
+        }
+        LARGE_INTEGER size{};
+        if (GetFileSizeEx(handle_, &size) == FALSE) return false;
+        size_ = static_cast<std::uint64_t>(size.QuadPart);
+        return true;
+    }
+
+    ~Window() {
+        if (handle_ != nullptr) CloseHandle(handle_);
+    }
+
+    std::uint64_t size() const { return size_; }
+
+    // Reads at an absolute offset; false when the range is not fully available.
+    bool read(std::uint64_t offset, void* destination, std::size_t bytes) const {
+        if (offset + bytes > size_) return false;
+        LARGE_INTEGER position{};
+        position.QuadPart = static_cast<LONGLONG>(offset);
+        if (SetFilePointerEx(handle_, position, nullptr, FILE_BEGIN) == FALSE) return false;
+        std::size_t done = 0;
+        auto* target = static_cast<std::uint8_t*>(destination);
+        while (done < bytes) {
+            const DWORD chunk = static_cast<DWORD>(
+                (bytes - done) > 0x10000u ? 0x10000u : (bytes - done));
+            DWORD got = 0;
+            if (ReadFile(handle_, target + done, chunk, &got, nullptr) == FALSE || got == 0) {
+                return false;
+            }
+            done += got;
+        }
+        return true;
+    }
+
+    bool load(std::uint64_t offset, std::size_t bytes, std::vector<std::uint8_t>* out) const {
+        out->assign(bytes, 0);
+        return bytes == 0 || read(offset, out->data(), bytes);
+    }
+
+private:
+    HANDLE handle_ = nullptr;
+    std::uint64_t size_ = 0;
+};
+
+// Set JOC_SCAN_TRACE=1 to have the walk printed: the practical way to see where a
+// container's structure stops matching what the probe expects.
+bool trace_enabled() {
+    static const bool enabled = [] {
+        return GetEnvironmentVariableA("JOC_SCAN_TRACE", nullptr, 0) != 0;
+    }();
+    return enabled;
+}
+
+void trace(const char* format, ...) {
+    if (!trace_enabled()) return;
+    va_list arguments;
+    va_start(arguments, format);
+    std::vfprintf(stdout, format, arguments);
+    va_end(arguments);
+    std::fflush(stdout);
+}
+
+std::uint32_t be32(const std::uint8_t* p) {
+    return (static_cast<std::uint32_t>(p[0]) << 24) | (static_cast<std::uint32_t>(p[1]) << 16) |
+           (static_cast<std::uint32_t>(p[2]) << 8) | static_cast<std::uint32_t>(p[3]);
+}
+
+std::string fourcc(const std::uint8_t* p) { return std::string(reinterpret_cast<const char*>(p), 4); }
+
+bool is_audio_sample_entry(const std::string& format) {
+    // E-AC-3 is "ec-3"; "ac-3" is plain Dolby Digital and is *not* ours.
+    return format == "ec-3" || format == "ec3 " || format == "EAC3";
+}
+
+bool is_ac3_sample_entry(const std::string& format) { return format == "ac-3" || format == "ac3 "; }
+
+// --- MP4 / ISO base media -------------------------------------------------
+
+// Walks the boxes inside [begin, end) and hands each to the visitor.
+template <typename Fn>
+bool walk_boxes(const Window& file, std::uint64_t begin, std::uint64_t end,
+                std::size_t depth, Fn visitor) {
+    std::uint64_t offset = begin;
+    std::uint8_t header[8];
+    while (offset + 8 <= end) {
+        if (!file.read(offset, header, sizeof(header))) return false;
+        std::uint64_t size = be32(header);
+        const std::string type = fourcc(header + 4);
+        std::uint64_t payload = offset + 8;
+        if (size == 1) {
+            std::uint8_t extended[8];
+            if (!file.read(offset + 8, extended, sizeof(extended))) return false;
+            size = (static_cast<std::uint64_t>(be32(extended)) << 32) | be32(extended + 4);
+            payload = offset + 16;
+        } else if (size == 0) {
+            size = end - offset;  // "to the end of the file"
+        }
+        trace("%*sbox %s size=%llu\n", static_cast<int>(depth) * 2, "", type.c_str(), static_cast<unsigned long long>(size));
+        if (size < 8 || offset + size > end) return false;
+        if (!visitor(type, payload, offset + size, depth)) return false;
+        offset += size;
+    }
+    return true;
+}
+
+// One trak: is it an audio track, and which sample entry does it use?
+struct TrackInfo {
+    bool audio = false;
+    std::string format;
+};
+
+bool scan_stbl(const Window& file, std::uint64_t begin, std::uint64_t end, TrackInfo* info) {
+    return walk_boxes(file, begin, end, 0, [&](const std::string& type, std::uint64_t payload,
+                                                std::uint64_t box_end, std::size_t) {
+        (void)box_end;
+        if (type == "stsd") {
+            std::uint8_t head[16];
+            if (file.read(payload, head, sizeof(head))) {
+                // version+flags(4) entry_count(4), then the first sample entry:
+                // size(4) format(4).
+                info->format = fourcc(head + 12);
+                trace("%*sstsd format=%s\n", 8, "", info->format.c_str());
+            }
+            return false;  // one sample entry is all the probe needs
+        }
+        return true;
+    });
+}
+
+// minf -> stbl -> stsd
+bool scan_minf(const Window& file, std::uint64_t begin, std::uint64_t end, TrackInfo* info) {
+    return walk_boxes(file, begin, end, 0, [&](const std::string& type, std::uint64_t payload,
+                                                std::uint64_t box_end, std::size_t) {
+        if (type == "stbl") scan_stbl(file, payload, box_end, info);
+        return true;
+    });
+}
+
+// mdia: the track handler says whether this is audio, minf leads to the sample entry.
+bool scan_mdia(const Window& file, std::uint64_t begin, std::uint64_t end, TrackInfo* info) {
+    return walk_boxes(file, begin, end, 0, [&](const std::string& type, std::uint64_t payload,
+                                                std::uint64_t box_end, std::size_t) {
+        if (type == "hdlr") {
+            std::uint8_t head[12];
+            if (file.read(payload, head, sizeof(head))) {
+                info->audio = fourcc(head + 8) == "soun";
+                trace("%*shdlr handler=%s audio=%d\n", 6, "", fourcc(head + 8).c_str(),
+                      info->audio ? 1 : 0);
+            }
+        } else if (type == "minf") {
+            scan_minf(file, payload, box_end, info);
+        }
+        return true;
+    });
+}
+
+// trak -> mdia
+bool scan_trak(const Window& file, std::uint64_t begin, std::uint64_t end, TrackInfo* info) {
+    return walk_boxes(file, begin, end, 0, [&](const std::string& type, std::uint64_t payload,
+                                                std::uint64_t box_end, std::size_t) {
+        if (type == "mdia") scan_mdia(file, payload, box_end, info);
+        return true;
+    });
+}
+Result scan_mp4(const Window& file, std::size_t max_bytes) {
+    Result result;
+    result.kind = Kind::kMp4;
+
+    // moov is usually at the start for streamed files and at the end otherwise.
+    struct Range {
+        std::uint64_t begin;
+        std::uint64_t end;
+    };
+    std::vector<Range> ranges{{0, (std::min<std::uint64_t>)(file.size(), max_bytes)}};
+    if (file.size() > max_bytes) {
+        ranges.push_back({file.size() - max_bytes, file.size()});
+    }
+
+    unsigned audio_seen = 0;
+    bool found_any_audio = false;
+    std::string first_audio_format;
+    for (const Range& range : ranges) {
+        walk_boxes(file, range.begin, range.end, 0,
+                   [&](const std::string& type, std::uint64_t payload, std::uint64_t box_end,
+                       std::size_t) {
+                       if (type != "moov") return true;
+                       walk_boxes(file, payload, box_end, 1,
+                                  [&](const std::string& inner, std::uint64_t inner_payload,
+                                      std::uint64_t inner_end, std::size_t) {
+                                      if (inner == "mvhd") {
+                                          // version(1) flags(3) then either
+                                          // creation/modification/timescale/duration (32-bit)
+                                          // or the 64-bit variant.
+                                          std::uint8_t header[32];
+                                          if (file.read(inner_payload, header, sizeof(header))) {
+                                              const bool wide = header[0] == 1;
+                                              const std::uint32_t timescale =
+                                                  wide ? be32(header + 20) : be32(header + 12);
+                                              const std::uint64_t duration =
+                                                  wide ? ((static_cast<std::uint64_t>(
+                                                               be32(header + 24))
+                                                           << 32) |
+                                                          be32(header + 28))
+                                                       : be32(header + 16);
+                                              if (timescale != 0) {
+                                                  result.duration_seconds =
+                                                      static_cast<double>(duration) /
+                                                      static_cast<double>(timescale);
+                                              }
+                                          }
+                                          return true;
+                                      }
+                                      if (inner != "trak") return true;
+                                      TrackInfo info;
+                                      scan_trak(file, inner_payload, inner_end, &info);
+                                      if (!info.audio) return true;
+                                      if (!found_any_audio) {
+                                          found_any_audio = true;
+                                          first_audio_format = info.format;
+                                      }
+                                      if (is_audio_sample_entry(info.format)) {
+                                          result.eac3 = true;
+                                          result.audio_index = audio_seen;
+                                          result.codec = info.format;
+                                      } else if (is_ac3_sample_entry(info.format)) {
+                                          result.codec = info.format;
+                                      }
+                                      ++audio_seen;
+                                      return !result.eac3;  // stop once found
+                                  });
+                       return !result.eac3;
+                   });
+        if (result.eac3) break;
+    }
+
+    if (result.eac3) {
+        result.detail = "mp4: E-AC-3 audio track " + std::to_string(result.audio_index);
+    } else if (found_any_audio) {
+        result.detail = "mp4: first audio track is " +
+                        (first_audio_format.empty() ? std::string("unknown")
+                                                    : first_audio_format);
+    } else {
+        result.detail = "mp4: no audio track found in the scanned window";
+    }
+    return result;
+}
+
+// --- Matroska / WebM ------------------------------------------------------
+
+struct EbmlReader {
+    const std::uint8_t* data = nullptr;
+    std::size_t size = 0;
+    std::size_t position = 0;
+
+    bool at_end() const { return position >= size; }
+
+    // Element IDs keep their leading bits; sizes drop the marker bit.
+    bool read_id(std::uint64_t* id) {
+        if (at_end()) return false;
+        const std::uint8_t first = data[position];
+        int length = 1;
+        for (int bit = 0x80; bit != 0; bit >>= 1, ++length) {
+            if ((first & bit) != 0) break;
+        }
+        if (length > 4 || position + static_cast<std::size_t>(length) > size) return false;
+        std::uint64_t value = 0;
+        for (int i = 0; i < length; ++i) value = (value << 8) | data[position + i];
+        position += static_cast<std::size_t>(length);
+        *id = value;
+        return true;
+    }
+
+    bool read_size(std::uint64_t* value, bool* unknown) {
+        *unknown = false;
+        if (at_end()) return false;
+        const std::uint8_t first = data[position];
+        int length = 1;
+        for (int bit = 0x80; bit != 0; bit >>= 1, ++length) {
+            if ((first & bit) != 0) break;
+        }
+        if (length > 8 || position + static_cast<std::size_t>(length) > size) return false;
+        std::uint64_t result = first & (0xFFu >> length);
+        bool all_ones = (first & (0xFFu >> length)) == (0xFFu >> length);
+        for (int i = 1; i < length; ++i) {
+            const std::uint8_t byte = data[position + i];
+            all_ones = all_ones && byte == 0xFFu;
+            result = (result << 8) | byte;
+        }
+        position += static_cast<std::size_t>(length);
+        *unknown = all_ones;
+        *value = result;
+        return true;
+    }
+};
+
+Result scan_matroska(const Window& file, std::size_t max_bytes) {
+    Result result;
+    result.kind = Kind::kMatroska;
+
+    std::vector<std::uint8_t> data;
+    if (!file.load(0, static_cast<std::size_t>(
+                         (std::min<std::uint64_t>)(file.size(), max_bytes)),
+                   &data)) {
+        result.detail = "matroska: cannot read the header";
+        return result;
+    }
+
+    unsigned audio_seen = 0;
+    std::string first_audio_codec;
+    bool saw_tracks = false;
+    bool found = false;
+    double timestamp_scale_ns = 1000000.0;  // Matroska default: 1 ms per tick
+    double duration_ticks = 0.0;
+
+    // Only the two levels that matter are walked: Tracks, then TrackEntry.
+    auto walk = [&](std::size_t begin, std::size_t end, int depth,
+                    auto&& self) -> void {
+        EbmlReader reader{data.data(), end, begin};
+        while (!reader.at_end() && !found) {
+            const std::size_t element_start = reader.position;
+            std::uint64_t id = 0;
+            std::uint64_t size = 0;
+            bool unknown = false;
+            if (!reader.read_id(&id) || !reader.read_size(&size, &unknown)) break;
+            std::size_t payload = reader.position;
+            std::size_t payload_end =
+                unknown ? end : (std::min<std::size_t>)(end, payload + static_cast<std::size_t>(size));
+            if (payload_end < payload) break;
+
+            switch (id) {
+                case 0x1654AE6Bu:  // Tracks
+                    saw_tracks = true;
+                    self(payload, payload_end, depth + 1, self);
+                    break;
+                case 0x1549A966u: {  // Info: carries the segment duration
+                    EbmlReader inner{data.data(), payload_end, payload};
+                    while (!inner.at_end()) {
+                        std::uint64_t child_id = 0;
+                        std::uint64_t child_size = 0;
+                        bool child_unknown = false;
+                        if (!inner.read_id(&child_id) ||
+                            !inner.read_size(&child_size, &child_unknown)) {
+                            break;
+                        }
+                        const std::size_t child_payload = inner.position;
+                        const std::size_t child_end =
+                            child_unknown ? payload_end
+                                          : (std::min<std::size_t>)(
+                                                payload_end,
+                                                child_payload + static_cast<std::size_t>(child_size));
+                        // TimestampScale (ns per tick, default 1 ms) and Duration (ticks).
+                        if (child_id == 0x2AD7B1u && child_size >= 1 && child_size <= 8) {
+                            std::uint64_t scale = 0;
+                            for (std::size_t i = 0; i < child_size; ++i) {
+                                scale = (scale << 8) | data[child_payload + i];
+                            }
+                            if (scale != 0) timestamp_scale_ns = scale;
+                        } else if (child_id == 0x4489u && (child_size == 4 || child_size == 8)) {
+                            // Duration is a big-endian float: 4 or 8 bytes, both occur.
+                            const std::uint8_t* field = data.data() + child_payload;
+                            if (child_size == 4) {
+                                const std::uint32_t bits = be32(field);
+                                float value = 0.0f;
+                                std::memcpy(&value, &bits, sizeof(value));
+                                duration_ticks = static_cast<double>(value);
+                            } else {
+                                const std::uint64_t bits =
+                                    (static_cast<std::uint64_t>(be32(field)) << 32) | be32(field + 4);
+                                double value = 0.0;
+                                std::memcpy(&value, &bits, sizeof(value));
+                                duration_ticks = value;
+                            }
+                        }
+                        inner.position = child_end;
+                    }
+                    break;
+                }
+                case 0xAEu: {  // TrackEntry
+                    // Read this track's type and codec.
+                    std::uint64_t track_type = 0;
+                    std::string codec;
+                    EbmlReader inner{data.data(), payload_end, payload};
+                    while (!inner.at_end()) {
+                        std::uint64_t child_id = 0;
+                        std::uint64_t child_size = 0;
+                        bool child_unknown = false;
+                        if (!inner.read_id(&child_id) ||
+                            !inner.read_size(&child_size, &child_unknown)) {
+                            break;
+                        }
+                        const std::size_t child_payload = inner.position;
+                        const std::size_t child_end =
+                            child_unknown ? payload_end
+                                          : (std::min<std::size_t>)(
+                                                payload_end,
+                                                child_payload + static_cast<std::size_t>(child_size));
+                        if (child_id == 0x83u && child_size >= 1) {  // TrackType
+                            track_type = data[child_payload];
+                        } else if (child_id == 0x86u) {  // CodecID
+                            codec.assign(reinterpret_cast<const char*>(data.data() + child_payload),
+                                         child_end - child_payload);
+                        }
+                        inner.position = child_end;
+                    }
+                    if (track_type == 2u) {  // audio
+                        if (first_audio_codec.empty()) first_audio_codec = codec;
+                        if (codec == "A_EAC3") {
+                            result.eac3 = true;
+                            result.audio_index = audio_seen;
+                            result.codec = codec;
+                            found = true;
+                        }
+                        ++audio_seen;
+                    }
+                    break;
+                }
+                case 0x18538067u:  // Segment: descend, the size may be unknown
+                    self(payload, payload_end, depth + 1, self);
+                    break;
+                default:
+                    break;
+            }
+            if (found) break;
+            reader.position = payload_end;
+            if (payload_end == element_start) break;  // no progress: stop
+        }
+    };
+    walk(0, data.size(), 0, walk);
+
+    if (duration_ticks > 0.0 && timestamp_scale_ns > 0.0) {
+        result.duration_seconds = duration_ticks * timestamp_scale_ns / 1.0e9;
+    }
+    if (result.eac3) {
+        result.detail = "matroska: E-AC-3 audio track " + std::to_string(result.audio_index);
+    } else if (saw_tracks) {
+        result.detail = "matroska: first audio track is " +
+                        (first_audio_codec.empty() ? std::string("unknown") : first_audio_codec);
+    } else {
+        result.detail = "matroska: no track list in the scanned window";
+    }
+    return result;
+}
+
+}  // namespace
+
+const char* kind_name(Kind kind) {
+    switch (kind) {
+        case Kind::kMp4: return "mp4";
+        case Kind::kMatroska: return "matroska";
+        default: return "none";
+    }
+}
+
+bool is_container_extension(const char* extension) {
+    if (extension == nullptr) return false;
+    static const char* const kExtensions[] = {"mp4", "m4a",  "m4b", "m4p", "m4r",
+                                              "mov", "mkv",  "mka", "webm"};
+    for (const char* candidate : kExtensions) {
+        if (_stricmp(extension, candidate) == 0) return true;
+    }
+    return false;
+}
+
+Result scan(const std::string& path, std::size_t max_bytes) {
+    Result result;
+    Window file;
+    if (!file.open(path)) {
+        result.detail = "cannot open the file";
+        return result;
+    }
+    if (file.size() < 16) {
+        result.detail = "file too small to be a container";
+        return result;
+    }
+
+    std::uint8_t head[16];
+    if (!file.read(0, head, sizeof(head))) {
+        result.detail = "cannot read the file header";
+        return result;
+    }
+    // Matroska starts with the EBML header element (0x1A45DFA3); ISO base media
+    // starts with a box whose type is at offset 4 ("ftyp" for a normal file).
+    if (head[0] == 0x1A && head[1] == 0x45 && head[2] == 0xDF && head[3] == 0xA3) {
+        result = scan_matroska(file, max_bytes);
+    } else {
+        result = scan_mp4(file, max_bytes);
+    }
+    joc_log::line("container: %s -> %s (eac3=%d audio#%u codec=%s)", path.c_str(),
+                  result.detail.c_str(), result.eac3 ? 1 : 0, result.audio_index,
+                  result.codec.empty() ? "-" : result.codec.c_str());
+    return result;
+}
+
+}  // namespace joc_container

src/container_scan.h

@@ -0,0 +1,47 @@
+// Cheap structural probe of container files, to answer one question: does this
+// file hold an E-AC-3 audio track, and if so which one?
+//
+// It exists so that a Media Library scan does not pay for an ffmpeg launch on
+// every MP4 in the collection.  The probe reads a bounded window of the file and
+// walks only the headers it needs:
+//
+//   MP4 / MOV  top-level boxes -> moov -> trak -> hdlr(mdia) + stsd sample entry.
+//              moov may sit at the end (no faststart), so the tail is checked too.
+//   Matroska   EBML header -> Segment -> Tracks -> TrackEntry -> CodecID.
+//
+// The E-AC-3 bitstream itself is never demuxed here: ffmpeg extracts it when the
+// file is actually decoded, which keeps this file small and lets every container
+// ffmpeg understands work without a demuxer of our own.
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+namespace joc_container {
+
+enum class Kind {
+    kNone,
+    kMp4,
+    kMatroska,
+};
+
+const char* kind_name(Kind kind);
+
+struct Result {
+    Kind kind = Kind::kNone;
+    bool eac3 = false;         // an E-AC-3 audio track is present
+    unsigned audio_index = 0;  // which audio track it is, 0-based
+    double duration_seconds = 0.0;  // from the container header, 0 when not stated
+    std::string codec;         // codec identifier found, for the log
+    std::string detail;
+};
+
+// True when the extension belongs to a container this component looks inside.
+bool is_container_extension(const char* extension);
+
+// Reads at most max_bytes of header (plus the same amount at the end for MP4) and
+// reports what it found.  Missing files, empty files and unknown containers come
+// back as Kind::kNone with a detail string.
+Result scan(const std::string& path, std::size_t max_bytes = 4u * 1024u * 1024u);
+
+}  // namespace joc_container

src/input_joc.cpp

@@ -18,6 +18,7 @@
 #include <cstring>
 #include <string>
 
+#include "container_scan.h"
 #include "eac3_scan.h"
 #include "joc_decode.h"
 #include "log.h"
@@ -62,6 +63,24 @@ public:
         input_open_file_helper(source, path, reason, abort);
         m_file = source;
 
+        // The core passes URLs ("file://C:\...").  ffmpeg and the file APIs need a
+        // native path, and a URL we cannot map to one is a file we cannot decode.
+        try {
+            m_native_path = filesystem::g_get_native_path(m_path.c_str());
+        } catch (const pfc::exception& error) {
+            joc_log::line("decoder: not a native file path (%s): %s", m_path.c_str(),
+                          error.what());
+            throw exception_io_unsupported_format();
+        }
+
+        const char* extension = std::strrchr(m_native_path.get_ptr(), '.');
+        extension = (extension != nullptr) ? extension + 1 : "";
+
+        if (joc_container::is_container_extension(extension)) {
+            open_container(extension);
+            return;
+        }
+
         pfc::array_t<t_uint8> buffer;
         buffer.set_size(kSniffBytes);
         const std::size_t got = m_file->read(buffer.get_ptr(), kSniffBytes, abort);
@@ -78,18 +97,43 @@ public:
             joc_log::line("decoder: yielding to the built-in decoder (%s)", scan.detail);
             throw exception_io_unsupported_format();
         }
-        joc_log::line("decoder: claiming this file as E-AC-3 JOC");
+        joc_log::line("decoder: claiming this file as E-AC-3 JOC (bare stream)");
+        m_input_kind = joc_decode::InputKind::kBare;
+    }
 
-        // The core passes URLs ("file://C:\...").  ffmpeg and the file APIs need a
-        // native path, and a URL we cannot map to one is a file we cannot decode.
-        try {
-            m_native_path = filesystem::g_get_native_path(m_path.c_str());
-        } catch (const pfc::exception& error) {
-            joc_log::line("decoder: not a native file path (%s): %s", m_path.c_str(),
-                            error.what());
+    // Two questions, in this order: is there an E-AC-3 track inside (answered from
+    // the container's own headers, so a library scan pays nothing for the MP4s that
+    // hold AAC), and does that track carry JOC (answered from a copied prefix of
+    // the track).  Either "no" hands the file to the next decoder in the table.
+    void open_container(const char* extension) {
+        m_container = joc_container::scan(m_native_path.get_ptr());
+        if (!m_container.eac3) {
+            joc_log::line("decoder: yielding to the built-in decoder (%s)",
+                          m_container.detail.c_str());
             throw exception_io_unsupported_format();
         }
-        joc_log::line("decoder: native path \"%s\"", m_native_path.get_ptr());
+
+        const joc_decode::Settings settings = joc_settings::current();
+        bool joc = false;
+        std::string detail;
+        if (!joc_decode::probe_container_joc(settings.ffmpeg_path, m_native_path.get_ptr(),
+                                            m_container.audio_index, &joc, &detail)) {
+            joc_log::line("decoder: cannot examine the E-AC-3 track (%s); yielding",
+                          detail.c_str());
+            throw exception_io_unsupported_format();
+        }
+        if (!joc) {
+            joc_log::line("decoder: yielding to the built-in decoder (E-AC-3 track %u carries "
+                          "no JOC: %s)",
+                          m_container.audio_index, detail.c_str());
+            throw exception_io_unsupported_format();
+        }
+
+        joc_log::line("decoder: claiming this file as E-AC-3 JOC (%s, audio track %u, .%s)",
+                      joc_container::kind_name(m_container.kind), m_container.audio_index,
+                      extension);
+        m_input_kind = joc_decode::InputKind::kContainer;
+        m_audio_index = m_container.audio_index;
     }
 
     void get_info(file_info& info, abort_callback& abort) {
@@ -97,6 +141,17 @@ public:
         const joc_decode::FileProbe probe = joc_decode::probe_file(m_native_path.get_ptr());
         const joc_decode::Settings settings = joc_settings::current();
 
+        // A container knows its own duration even though the E-AC-3 syncframes are
+        // not directly addressable in the file.
+        const bool container = (m_input_kind == joc_decode::InputKind::kContainer);
+        const double duration = (container && m_container.duration_seconds > 0.0)
+                                    ? m_container.duration_seconds
+                                    : probe.duration_seconds;
+        const std::uint64_t frames =
+            probe.frames != 0
+                ? probe.frames
+                : ((duration > 0.0) ? static_cast<std::uint64_t>(duration * 48000.0 / 1536.0) : 0);
+
         unsigned channels = 2;
         std::string render;
         if (settings.output == joc_decode::Output::kBinaural) {
@@ -115,12 +170,12 @@ public:
         info.info_set_int("channels", channels);
         info.info_set_int("bitspersample", 32);
         info.info_set("bitspersample_extra", "floating-point");
-        info.set_length(probe.duration_seconds);
-        if (probe.duration_seconds > 0.0) {
+        info.set_length(duration);
+        if (duration > 0.0) {
             const t_filesize bytes = m_file.is_valid() ? m_file->get_size(abort) : filesize_invalid;
             if (bytes != filesize_invalid && bytes > 0) {
                 info.info_set_bitrate(static_cast<t_int64>(
-                    static_cast<double>(bytes) * 8.0 / probe.duration_seconds / 1000.0));
+                    static_cast<double>(bytes) * 8.0 / duration / 1000.0));
             }
         }
         // Custom fields: visible in Properties and usable as %joc_*% in title
@@ -129,11 +184,19 @@ public:
         info.info_set("joc_hrtf", settings.hrtf_file.empty()
                                       ? "(未设置)"
                                       : file_name_of(settings.hrtf_file).c_str());
-        info.info_set_int("joc_frames", static_cast<t_int64>(probe.frames));
-        info.info_set("joc_scan", probe.detail.c_str());
-        joc_log::line("decoder: get_info duration=%.3f s frames=%llu channels=%u render=%s",
-                        probe.duration_seconds, static_cast<unsigned long long>(probe.frames),
-                        channels, render.c_str());
+        info.info_set_int("joc_frames", static_cast<t_int64>(frames));
+        info.info_set("joc_scan", container ? m_container.detail.c_str() : probe.detail.c_str());
+        if (container) {
+            char text[128] = {};
+            std::snprintf(text, sizeof(text), "%s (%s, audio track %u)",
+                          joc_container::kind_name(m_container.kind),
+                          m_container.codec.empty() ? "E-AC-3" : m_container.codec.c_str(),
+                          m_container.audio_index);
+            info.info_set("joc_container", text);
+        }
+        joc_log::line("decoder: get_info duration=%.3f s frames=%llu channels=%u render=%s%s",
+                      duration, static_cast<unsigned long long>(frames), channels, render.c_str(),
+                      container ? " (container)" : "");
     }
 
     t_filestats2 get_stats2(uint32_t flags, abort_callback& abort) {
@@ -144,6 +207,8 @@ public:
     void decode_initialize(unsigned flags, abort_callback& abort) {
         (void)abort;
         m_settings = joc_settings::current();
+        m_settings.input_kind = m_input_kind;
+        m_settings.audio_index = m_audio_index;
         joc_log::line("decoder: initialize flags=0x%X settings: %s", flags,
                         joc_settings::describe(m_settings).c_str());
 
@@ -224,18 +289,28 @@ public:
 
     static bool g_is_our_path(const char* path, const char* extension) {
         (void)path;
-        // Claim by extension, then decide from the bitstream in open(): a file that
-        // turns out not to carry JOC is handed back with
-        // exception_io_unsupported_format, and the core moves on to the next
-        // decoder in its priority table.
+        // Claim by extension, then decide from the contents in open(): a file whose
+        // audio turns out not to be E-AC-3 JOC is handed back with
+        // exception_io_unsupported_format, and the core moves on to the next decoder
+        // in its priority table.  Containers are included because an E-AC-3 JOC
+        // track is commonly wrapped in MP4 or Matroska; the container walk in
+        // open() is what keeps the other files cheap to decline.
+        if (joc_container::is_container_extension(extension)) return true;
         return (extension != nullptr) &&
                ((stricmp_utf8(extension, "eac3") == 0) || (stricmp_utf8(extension, "ec3") == 0));
     }
 
     static bool g_is_our_content_type(const char* content_type) {
-        (void)content_type;
-        // Container dispatch (MP4 ec-3, Matroska A_EAC3) is not claimed: only bare
-        // E-AC-3 streams are handled, so let the container readers have them.
+        if (content_type == nullptr) return false;
+        // E-AC-3 content types, and only the E-AC-3 ones: the generic Dolby aliases
+        // are deliberately left alone, because a track the core can already decode
+        // must not end up claimed by an entry that will not decode it.
+        static const char* const kTypes[] = {"audio/eac3", "audio/eac3joc", "audio/ec3",
+                                            "audio/x-eac3", "E-AC-3",      "eac3",
+                                            "ec3"};
+        for (const char* candidate : kTypes) {
+            if (stricmp_utf8(content_type, candidate) == 0) return true;
+        }
         return false;
     }
 
@@ -250,6 +325,11 @@ private:
     pfc::string8 m_native_path;
     joc_decode::Settings m_settings;
     joc_decode::Engine m_engine;
+    // Set by open(): a bare stream is read directly, an E-AC-3 track inside a
+    // container is extracted by ffmpeg before it reaches the renderer.
+    joc_decode::InputKind m_input_kind = joc_decode::InputKind::kBare;
+    unsigned m_audio_index = 0;
+    joc_container::Result m_container;
     std::vector<float> m_buffer;
     unsigned m_channels = 2;
     std::uint64_t m_frames_delivered = 0;

src/joc_decode.cpp

@@ -88,19 +88,24 @@ const char* error_text(const CoreApi& api, joc_error code) {
 // ---------------------------------------------------------------------------
 // ffmpeg child process producing the 5.1 core PCM on a pipe.
 // ---------------------------------------------------------------------------
-class BedProcess {
+class FfmpegPipe {
 public:
-    ~BedProcess() { stop(); }
+    ~FfmpegPipe() { stop(); }
 
+    // ffmpeg_path, the input file and whatever should follow "-i <input>" are
+    // separate: the 5.1 bed and the E-AC-3 metadata stream of a container file are
+    // both ffmpeg output, they only differ in those arguments.
     bool start(const std::string& ffmpeg_path, const std::string& input_path,
-               const std::wstring& stderr_path, std::string* error) {
+               const std::wstring& output_arguments, const char* label,
+               const std::wstring& stderr_path, std::string* error,
+               std::size_t pipe_bytes = kBedPipeBytes) {
         SECURITY_ATTRIBUTES attributes{};
         attributes.nLength = sizeof(attributes);
         attributes.bInheritHandle = TRUE;
         HANDLE read_end = nullptr;
         HANDLE write_end = nullptr;
-        if (CreatePipe(&read_end, &write_end, &attributes, static_cast<DWORD>(kBedPipeBytes)) == FALSE) {
-            if (error != nullptr) *error = "cannot create the core PCM pipe";
+        if (CreatePipe(&read_end, &write_end, &attributes, static_cast<DWORD>(pipe_bytes)) == FALSE) {
+            if (error != nullptr) *error = std::string("cannot create the ") + label + " pipe";
             return false;
         }
         // Only the child's end is inheritable.
@@ -115,10 +120,8 @@ public:
         std::wstring command = L"\"" + utf8_to_wide(ffmpeg_path) + L"\"";
         command += L" -hide_banner -loglevel error -nostdin -y -i \"";
         command += utf8_to_wide(input_path);
-        // Identical to the reference CLI's core decode: 5.1 interleaved float32
-        // at 48 kHz, which is the layout the rendering core expects
-        // (L R C LFE Ls Rs).
-        command += L"\" -map 0:a:0 -vn -ac 6 -ar 48000 -c:a pcm_f32le -f f32le -";
+        command += L"\" ";
+        command += output_arguments;
 
         STARTUPINFOW startup{};
         startup.cb = sizeof(startup);
@@ -138,13 +141,13 @@ public:
         if (error_file != INVALID_HANDLE_VALUE) CloseHandle(error_file);
         if (created == FALSE) {
             CloseHandle(read_end);
-            if (error != nullptr) *error = "cannot start ffmpeg for the 5.1 core PCM";
+            if (error != nullptr) *error = std::string("cannot start ffmpeg for the ") + label;
             return false;
         }
         CloseHandle(process.hThread);
         pipe_ = read_end;
         process_ = process.hProcess;
-        joc_log::line("core bed: ffmpeg started (pid %lu)", process.dwProcessId);
+        joc_log::line("core %s: ffmpeg started (pid %lu)", label, process.dwProcessId);
         return true;
     }
 
@@ -341,15 +344,109 @@ FileProbe probe_file(const std::string& path, std::size_t max_scan_bytes) {
     return probe;
 }
 
+// ---------------------------------------------------------------------------
+// JOC verdict for a container file, without rendering anything.
+// ---------------------------------------------------------------------------
+bool probe_container_joc(const std::string& ffmpeg_path, const std::string& path,
+                         unsigned audio_index, bool* joc, std::string* detail) {
+    struct Entry {
+        std::string path;
+        unsigned audio_index = 0;
+        std::uint64_t size = 0;
+        std::uint64_t modified = 0;
+        bool joc = false;
+        std::string detail;
+    };
+    static std::vector<Entry> cache;
+
+    std::uint64_t size = 0;
+    std::uint64_t modified = 0;
+    {
+        WIN32_FILE_ATTRIBUTE_DATA data{};
+        if (GetFileAttributesExW(utf8_to_wide(path).c_str(), GetFileExInfoStandard, &data) !=
+            FALSE) {
+            size = (static_cast<std::uint64_t>(data.nFileSizeHigh) << 32) | data.nFileSizeLow;
+            modified = (static_cast<std::uint64_t>(data.ftLastWriteTime.dwHighDateTime) << 32) |
+                       data.ftLastWriteTime.dwLowDateTime;
+        }
+    }
+    for (const Entry& entry : cache) {
+        if (entry.path == path && entry.audio_index == audio_index && entry.size == size &&
+            entry.modified == modified) {
+            if (joc != nullptr) *joc = entry.joc;
+            if (detail != nullptr) *detail = entry.detail;
+            return true;
+        }
+    }
+
+    if (ffmpeg_path.empty()) {
+        if (detail != nullptr) *detail = "no ffmpeg configured";
+        return false;
+    }
+
+    FfmpegPipe pipe;
+    std::string error;
+    std::wstring arguments = L"-map 0:a:";
+    arguments += std::to_wstring(audio_index);
+    arguments += L" -vn -t 3 -c:a copy -f eac3 -";
+    const std::wstring stderr_path = [] {
+        wchar_t temp[MAX_PATH + 1] = {};
+        const DWORD length = GetTempPathW(MAX_PATH, temp);
+        return length == 0 ? std::wstring(L"NUL")
+                           : std::wstring(temp) + L"joc_container_probe.log";
+    }();
+    if (!pipe.start(ffmpeg_path, path, arguments, "probe", stderr_path, &error, 1u << 20)) {
+        if (detail != nullptr) *detail = error;
+        return false;
+    }
+
+    std::vector<std::uint8_t> prefix(512u * 1024u);
+    std::size_t filled = 0;
+    while (filled < prefix.size()) {
+        const std::size_t got = pipe.read(prefix.data() + filled, prefix.size() - filled);
+        if (got == 0) break;
+        filled += got;
+    }
+    pipe.stop();
+
+    const joc_eac3::ScanResult scan = joc_eac3::scan(prefix.data(), filled, 8);
+    const bool carries_joc = (scan.joc == joc_eac3::JocState::kYes);
+
+    Entry entry;
+    entry.path = path;
+    entry.audio_index = audio_index;
+    entry.size = size;
+    entry.modified = modified;
+    entry.joc = carries_joc;
+    entry.detail = scan.detail;
+    if (cache.size() >= 8) cache.erase(cache.begin());
+    cache.push_back(entry);
+
+    joc_log::line("container: %s track %u -> %s (%s)", path.c_str(), audio_index,
+                  carries_joc ? "JOC" : "not JOC", scan.detail);
+    if (joc != nullptr) *joc = carries_joc;
+    if (detail != nullptr) *detail = scan.detail;
+    return true;
+}
+
 // ---------------------------------------------------------------------------
 // Engine
 // ---------------------------------------------------------------------------
 struct Engine::Impl {
     CoreApi api;
     joc_stream* stream = nullptr;
-    InputFile eac3;
-    BedProcess bed;
+    InputFile eac3;        // bare E-AC-3 input: read straight from the file
+    FfmpegPipe eac3_pipe;  // E-AC-3 inside a container: ffmpeg extracts the stream
+    bool eac3_from_pipe = false;
+    FfmpegPipe bed;
     Settings settings;
+
+    // The metadata stream comes either from the file itself or from ffmpeg.
+    std::size_t read_eac3(void* destination, std::size_t bytes) {
+        return eac3_from_pipe ? eac3_pipe.read(destination, bytes)
+                              : eac3.read(destination, bytes);
+    }
+
     unsigned channels = 0;
     std::uint64_t frames_queued = 0;    // E-AC-3 frames handed to the core
     std::uint64_t bed_frames_pushed = 0;
@@ -382,7 +479,9 @@ void Engine::stop() {
         impl.stream = nullptr;
     }
     impl.bed.stop();
+    impl.eac3_pipe.stop();
     impl.eac3.close();
+    impl.eac3_from_pipe = false;
 }
 
 bool Engine::start(const std::string& input_path, const Settings& settings, std::string* error) {
@@ -402,9 +501,15 @@ bool Engine::start(const std::string& input_path, const Settings& settings, std:
         return false;
     }
 
-    if (!impl.eac3.open(input_path)) {
-        if (error != nullptr) *error = "cannot open the input file";
-        return false;
+    // Metadata stream: a bare E-AC-3 file is read directly, while the E-AC-3 track
+    // of a container is extracted by ffmpeg (stream copy, so the syncframes reach
+    // the renderer exactly as stored).
+    impl.eac3_from_pipe = (settings.input_kind == InputKind::kContainer);
+    if (!impl.eac3_from_pipe) {
+        if (!impl.eac3.open(input_path)) {
+            if (error != nullptr) *error = "cannot open the input file";
+            return false;
+        }
     }
 
     joc_stream_config config{};
@@ -479,20 +584,46 @@ bool Engine::start(const std::string& input_path, const Settings& settings, std:
                     settings.speaker_layout.c_str(),
                     hrtf_in_use.empty() ? "(none)" : hrtf_in_use.c_str());
 
-    const std::wstring stderr_path = [] {
+    // ffmpeg's stderr lands next to the component rather than in whatever working
+    // directory the host process happens to have.  The two children write separate
+    // files so neither can truncate the other's diagnostics.
+    const auto stderr_path_for = [](const wchar_t* name) {
         HMODULE self = nullptr;
         GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS |
                                GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT,
                            reinterpret_cast<LPCWSTR>(&speaker_channels), &self);
         wchar_t path[4096] = {};
         const DWORD length = GetModuleFileNameW(self, path, 4096);
-        if (length == 0) return std::wstring(L"joc_ffmpeg.log");
+        if (length == 0) return std::wstring(name);
         const std::wstring text(path, length);
         const std::wstring::size_type slash = text.find_last_of(L"\\/");
-        return slash == std::wstring::npos ? std::wstring(L"joc_ffmpeg.log")
-                                          : text.substr(0, slash) + L"\\joc_ffmpeg.log";
-    }();
-    if (!impl.bed.start(settings.ffmpeg_path, input_path, stderr_path, error)) return false;
+        return slash == std::wstring::npos ? std::wstring(name)
+                                          : text.substr(0, slash) + L"\\" + name;
+    };
+
+    // The 5.1 core PCM, exactly as the reference renderer's own core decode does it:
+    // 5.1 interleaved float32 at 48 kHz, the layout the renderer expects
+    // (L R C LFE Ls Rs).
+    std::wstring bed_arguments = L"-map 0:a:";
+    bed_arguments += std::to_wstring(settings.audio_index);
+    bed_arguments += L" -vn -ac 6 -ar 48000 -c:a pcm_f32le -f f32le -";
+    if (!impl.bed.start(settings.ffmpeg_path, input_path, bed_arguments, "bed",
+                        stderr_path_for(L"joc_ffmpeg_bed.log"), error)) {
+        return false;
+    }
+
+    if (impl.eac3_from_pipe) {
+        // Stream copy: the syncframes arrive byte for byte as they are stored, which
+        // is what the JOC metadata needs.
+        std::wstring stream_arguments = L"-map 0:a:";
+        stream_arguments += std::to_wstring(settings.audio_index);
+        stream_arguments += L" -vn -c:a copy -f eac3 -";
+        if (!impl.eac3_pipe.start(settings.ffmpeg_path, input_path, stream_arguments, "metadata",
+                                  stderr_path_for(L"joc_ffmpeg_stream.log"), error,
+                                  1u << 20)) {
+            return false;
+        }
+    }
     return true;
 }
 
@@ -534,7 +665,7 @@ std::size_t Engine::read(float* destination, std::size_t frames, std::string* er
             // across chunk boundaries: counting each chunk on its own loses one
             // frame at the end, which leaves the bed a frame short and the last
             // frame of the file unrendered.
-            const std::size_t got = impl.eac3.read(impl.eac3_buffer.data() + impl.eac3_carry,
+            const std::size_t got = impl.read_eac3(impl.eac3_buffer.data() + impl.eac3_carry,
                                                    impl.eac3_buffer.size() - impl.eac3_carry);
             const std::size_t total = impl.eac3_carry + got;
             if (total == 0) {

src/joc_decode.h

@@ -35,8 +35,18 @@ enum class HrtfSource {
     kRosella = 1,
 };
 
+// Where the E-AC-3 syncframes come from.  A bare stream is read straight from the
+// file; inside a container the track has to be extracted first (ffmpeg, stream copy).
+enum class InputKind {
+    kBare = 0,
+    kContainer = 1,
+};
+
 struct Settings {
     Output output = Output::kBinaural;
+    InputKind input_kind = InputKind::kBare;
+    // Which of the container's audio tracks holds the E-AC-3 stream, 0-based.
+    unsigned audio_index = 0;
     std::string speaker_layout = "7.1";
     HrtfSource hrtf_source = HrtfSource::kSofa;
     // Empty means the default file in the default folder, see resolve_hrtf_file().
@@ -87,6 +97,14 @@ struct FileProbe {
 // does pointer arithmetic over the stream, no decoding, no HRTF work.
 FileProbe probe_file(const std::string& path, std::size_t max_scan_bytes = 0);
 
+// Decides whether the E-AC-3 track of a container file carries JOC, without
+// rendering anything: ffmpeg copies a short prefix of that track out (stream copy,
+// so the syncframes are the stored ones) and the same bitstream test is applied.
+// The verdict is cached per file, because the information and the decode pass would
+// otherwise each launch ffmpeg for it.
+bool probe_container_joc(const std::string& ffmpeg_path, const std::string& path,
+                         unsigned audio_index, bool* joc, std::string* detail);
+
 class Engine {
 public:
     Engine();

src/main.cpp

@@ -8,7 +8,6 @@
 #include <SDK/componentversion.h>
 #include <SDK/coreversion.h>
 #include <SDK/initquit.h>
-
 #include "log.h"
 
 // Kept in one place: the string reported to foobar2000 and written to the log

tests/container_scan_test.cpp

@@ -0,0 +1,31 @@
+// Exercises the container probe directly, without going through foobar2000.
+//
+//   container_scan_test <file> [more files...]
+//
+// It exists because container dispatch is decided by the core's decoder priority
+// table: when a built-in demuxer is offered the file first, this component never
+// sees it, so the probe would otherwise never run during a test.  Running it here
+// shows what the probe decides for each file on its own.
+
+#include <cstdio>
+#include <string>
+
+#include "../src/container_scan.h"
+
+int main(int argc, char** argv) {
+    if (argc < 2) {
+        std::fprintf(stderr, "usage: container_scan_test <file> [more files...]\n");
+        return 2;
+    }
+    int failures = 0;
+    for (int i = 1; i < argc; ++i) {
+        const std::string path = argv[i];
+        const joc_container::Result result = joc_container::scan(path);
+        std::printf("%-28s kind=%-9s eac3=%d audio#%u codec=%-6s duration=%8.3f s  %s\n",
+                    path.c_str(), joc_container::kind_name(result.kind), result.eac3 ? 1 : 0,
+                    result.audio_index, result.codec.empty() ? "-" : result.codec.c_str(),
+                    result.duration_seconds, result.detail.c_str());
+        if (result.kind == joc_container::Kind::kNone) ++failures;
+    }
+    return failures == 0 ? 0 : 1;
+}

tools/build_tests.ps1

@@ -39,10 +39,11 @@ $lines = @(
     "call `"$vcvars`" >nul",
     "cd /d `"$projectRoot`"",
     # log.cpp comes along because the engine writes its diagnostics through it.
+    "cl $common /Fe:`"$outDir\container_scan_test.exe`" /Fo:`"$outDir\\`" tests\container_scan_test.cpp src\container_scan.cpp src\log.cpp",
     "cl $common /Fe:`"$outDir\scan_selftest.exe`" /Fo:`"$outDir\\`" tests\scan_selftest.cpp src\eac3_scan.cpp",
     "cl $common /Fe:`"$outDir\prefs_layout_check.exe`" /Fo:`"$outDir\\`" tests\prefs_layout_check.cpp user32.lib gdi32.lib",
     "cl $common /Fe:`"$outDir\scan_crosscheck.exe`" /Fo:`"$outDir\\`" tests\scan_crosscheck.cpp src\eac3_scan.cpp `"$coreLib`" shell32.lib",
-    "cl $common /Fe:`"$outDir\render_harness.exe`" /Fo:`"$outDir\\`" tests\render_harness.cpp src\joc_decode.cpp src\eac3_scan.cpp src\log.cpp `"$coreLib`" shell32.lib",
+    "cl $common /Fe:`"$outDir\render_harness.exe`" /Fo:`"$outDir\\`" tests\render_harness.cpp src\joc_decode.cpp src\eac3_scan.cpp src\container_scan.cpp src\log.cpp `"$coreLib`" shell32.lib",
     'if errorlevel 1 exit /b 1',
     'exit /b 0'
 )