src 与 MSE：两种输入，两套集成

URL 与 MSE 共用控制桥接；资源分别以 URL 参数或 DemuxerStream endpoints 交接。

1. 入口WebMediaPlayerImpl::Load() → DoLoad()

   加载入口；后续创建 demuxer 和启动 pipeline。

   third_party/blink/renderer/platform/media/web_media_player_impl.cc:739

   737: }
   738: 
   739: WebMediaPlayer::LoadTiming WebMediaPlayerImpl::Load(
   740:     LoadType load_type,
   741:     const WebMediaPlayerSource& source,
   742:     CorsMode cors_mode,
   743:     bool is_cache_disabled) {
   744:   // Only URL or MSE blob URL is supported.
   745:   DCHECK(source.IsURL());
   746:   WebURL url = source.GetAsURL();
   747:   DVLOG(1) << __func__ << "(" << load_type << ", " << GURL(url) << ", "

2. 异步生命周期WebMediaPlayerImpl::StartPipeline()

   调用 DemuxerManager::CreateDemuxer()；PipelineController 管理状态。

   third_party/blink/renderer/platform/media/web_media_player_impl.cc:3823

   3821: }
   3822: 
   3823: void WebMediaPlayerImpl::StartPipeline() {
   3824:   DCHECK(main_task_runner_->BelongsToCurrentThread());
   3825: 
   3826:   vfc_task_runner_->PostTask(
   3827:       FROM_HERE,
   3828:       base::BindOnce(&VideoFrameCompositor::SetOnNewProcessedFrameCallback,
   3829:                      base::Unretained(compositor_.get()),
   3830:                      base::BindPostTaskToCurrentDefault(base::BindOnce(
   3831:                          &WebMediaPlayerImpl::OnFirstFrame, weak_this_))));

3. 工厂选择MediaPlayerRendererClientFactory::CreateRenderer()

   建立 Mojo renderer 及双向扩展接口；由 MediaFactory 选择此工厂。

   tizen_src/chromium_impl/content/renderer/media/tizen/media_player_renderer_client_factory.cc:23

   21: 
   22: std::unique_ptr<media::Renderer>
   23: MediaPlayerRendererClientFactory::CreateRenderer(
   24:     const scoped_refptr<base::SequencedTaskRunner>& media_task_runner,
   25:     const scoped_refptr<base::TaskRunner>& worker_task_runner,
   26:     media::AudioRendererSink* audio_renderer_sink,
   27:     media::VideoRendererSink* video_renderer_sink,
   28:     media::RequestOverlayInfoCB request_overlay_info_cb,
   29:     const gfx::ColorSpace& target_color_space) {
   30:   // Used to send messages from the MPRC (Renderer process), to the MPR (Browser
   31:   // process). The |renderer_extension_request| will be bound in

4. Mojo IPC / 创建MediaInterfaceProxy::CreateMediaPlayerRenderer()

   browser 创建 TizenRendererImpl，交给 MojoRendererService 托管。

   content/browser/media/media_interface_proxy.cc:435

   433:   media::MojoRendererService::Create(
   434:       nullptr,
   435:       std::make_unique<content::TizenRendererImpl>(
   436:           render_frame_host().GetProcess()->GetID(),
   437:           render_frame_host().GetRoutingID(),
   438:           WebContents::FromRenderFrameHost(&render_frame_host()),
   439:           std::move(renderer_extension_receiver),
   440:           std::move(client_extension_remote)),
   441:       std::move(receiver));
   442: }
   443: #endif

5. 初始化阶段MediaPlayerRendererClient::Initialize() → MojoRendererWrapper::Initialize()

   renderer 侧包装层将初始化转给 MojoRenderer。

   tizen_src/chromium_impl/content/renderer/media/tizen/media_player_renderer_client.cc:46

   44: }
   45: 
   46: void MediaPlayerRendererClient::Initialize(
   47:     media::MediaResource* media_resource,
   48:     media::RendererClient* client,
   49:     media::PipelineStatusCallback init_cb) {
   50:   DCHECK(media_task_runner_->RunsTasksInCurrentSequence());
   51:   DCHECK(!init_cb_);
   52: 
   53:   LOG(INFO) << "MediaPlayerRendererClient Initialize:" << (void*)this;
   54: 

6. 资源类型分支MojoRenderer::InitializeRendererFromUrl() / InitializeRendererFromStreams()

   URL 发送 MediaUrlParams；stream 绑定 MojoDemuxerStreamImpl 并发送 endpoints。

   media/mojo/clients/mojo_renderer.cc:63

   61:   init_cb_ = std::move(init_cb);
   62: 
   63:   switch (media_resource_->GetType()) {
   64:     case MediaResource::Type::kStream:
   65:       InitializeRendererFromStreams(client);
   66:       break;
   67:     case MediaResource::Type::KUrl:
   68:       InitializeRendererFromUrl(client);
   69:       break;
   70:   }
   71: }

7. Mojo IPC / 异步就绪MojoRendererService::Initialize() / OnAllStreamsReady()

   URL 重建 MediaUrlDemuxer；stream 建立 MediaResourceShim，流就绪后调用 renderer。

   media/mojo/services/mojo_renderer_service.cc:56

   54: MojoRendererService::~MojoRendererService() = default;
   55: 
   56: void MojoRendererService::Initialize(
   57:     mojo::PendingAssociatedRemote<mojom::RendererClient> client,
   58:     std::optional<std::vector<mojo::PendingRemote<mojom::DemuxerStream>>>
   59:         streams,
   60:     mojom::MediaUrlParamsPtr media_url_params,
   61:     InitializeCallback callback) {
   62:   LOG(INFO) << "MojoRendererService Initialize:" << (void*)this;
   63:   DCHECK_EQ(state_, STATE_UNINITIALIZED);
   64: 

8. browser 平台桥接TizenRendererImpl::Initialize() → MediaPlayerRegistry::CreateMediaPlayer()

   按资源类型选择平台工厂，创建并初始化原生播放器。

   tizen_src/chromium_impl/content/browser/media/tizen_renderer_impl.cc:202

   200: 
   201:   // Create a media player and get player id for the created media player.
   202:   media_player_ = media::MediaPlayerRegistry::GetInstance()->CreateMediaPlayer(
   203:       media_resource_, user_agent, client_, volume_, player_id_);
   204: 
   205: #if BUILDFLAG(IS_TIZEN_TV)
   206:   client_extension_->UpdateVideoId(player_id_);
   207:   media_player_->SetContentMimeType(mime_type_);
   208: #endif
   209: 
   210:   if (!media_player_->CreatePlayer(player_id_)) {

展示 Tizen TV 的普通平台 URL 路径；音频、upstream 模式和 HbbTV 等条件分支另列。

1. URL 路径选择ContentRendererClient::OverrideDemuxerForUrl()

   TV / 非 upstream 模式下可用 MediaUrlDemuxer；MSE 或音频条件直接返回 nullptr。

   content/public/renderer/content_renderer_client.cc:188

   186: #endif
   187: 
   188: std::unique_ptr<media::Demuxer> ContentRendererClient::OverrideDemuxerForUrl(
   189:     RenderFrame* render_frame,
   190:     const GURL& url,
   191: #if BUILDFLAG(IS_TIZEN_TV)
   192:     bool is_media_source,
   193: #endif
   194:     scoped_refptr<base::SequencedTaskRunner> task_runner) {
   195: #if defined(TIZEN_MULTIMEDIA) && BUILDFLAG(IS_TIZEN_TV)
   196:   if (media::IsUpstreamArchitectureEnabled()) {

2. 资源创建DemuxerManager::CreateDemuxer()

   管理 URL demuxer / override；这里的 MediaUrlDemuxer 是 URL 资源桥，不负责拆出平台媒体包。

   media/filters/demuxer_manager.cc:393

   391: }
   392: 
   393: PipelineStatus DemuxerManager::CreateDemuxer(
   394:     bool load_media_source,
   395: #if defined(SAMSUNG_ELEMENTARY_MEDIA_STREAM_SOURCE)
   396:     bool load_elementary_media_stream_source,
   397: #endif  // defined(SAMSUNG_ELEMENTARY_MEDIA_STREAM_SOURCE)
   398:     DataSource::Preload preload,
   399:     bool needs_first_frame,
   400:     DemuxerManager::DemuxerCreatedCB on_demuxer_created,
   401:     base::flat_map<std::string, std::string> headers) {

3. Mojo IPC / URL 参数MojoRenderer::InitializeRendererFromUrl()

   将媒体 URL 与相关请求参数发送到 browser；共用初始化链见上一节。

   media/mojo/clients/mojo_renderer.cc:109

   107: }
   108: 
   109: void MojoRenderer::InitializeRendererFromUrl(media::RendererClient* client) {
   110:   DVLOG(2) << __func__;
   111:   DCHECK(task_runner_->RunsTasksInCurrentSequence());
   112: 
   113:   BindRemoteRendererIfNeeded();
   114: 
   115:   const MediaUrlParams& url_params = media_resource_->GetMediaUrlParams();
   116: 
   117:   // Using base::Unretained(this) is safe because |this| owns

4. browser 工厂分支MediaPlayerRegistry::CreateMediaPlayer()

   URL 默认选择 BridgeCapi 工厂；启用 PlusPlayer 的 HbbTV 构建存在独立分支。

   tizen_src/chromium_impl/media/filters/media_player_registry.cc:63

   61: }
   62: 
   63: std::unique_ptr<MediaPlayerTizen> MediaPlayerRegistry::CreateMediaPlayer(
   64:     MediaResource* media_resource,
   65:     const std::string& user_agent,
   66:     media::RendererClient* client,
   67:     double volume,
   68:     int& player_id) {
   69:   LOG(INFO) << __func__;
   70:   std::unique_ptr<MediaPlayerFactory> factory;
   71:   if (media_resource->GetType() == MediaResource::Type::kStream) {

5. TV 编译分支MediaPlayerBridgeCapiFactory::Create()

   IS_TIZEN_TV 创建 MediaPlayerBridgeCapiTV，其他构建使用 common 类。

   tizen_src/chromium_impl/media/filters/media_player_bridge_capi_factory.cc:28

   26:             << media_resource->GetMediaUrlParams().media_url.spec()
   27:             << ", clean url: " << clean_url.spec();
   28:   return std::make_unique<MediaPlayerBridgeCapiTV>(clean_url, user_agent,
   29:                                                    volume);
   30: #else
   31:   return std::make_unique<MediaPlayerBridgeCapi>(
   32:       media_resource->GetMediaUrlParams().media_url, user_agent, volume);
   33: #endif
   34: }
   35: 
   36: }  // namespace media

6. 平台 API / 配置MediaPlayerBridgeCapi::Prepare() → player_set_uri()

   普通 TV URL 在 Prepare 中交给平台；HbbTV 可使用 TV 子类的 URL 配置分支。

   tizen_src/chromium_impl/media/filters/media_player_bridge_capi.cc:242

   240:       LOG(INFO) << "Blob URL detected, using temp file: " << url_str;
   241:     }
   242:     player_set_uri(player_, url_str.c_str());
   243:   }
   244: #else
   245:   player_set_uri(player_, url_.spec().c_str());
   246: #endif
   247: 
   248: #if !defined(EWK_BRINGUP)
   249:   player_set_sound_type(player_, SOUND_TYPE_MEDIA);
   250: #endif

7. 平台异步准备Prepare() → player_prepare_async()

   准备过程异步完成；不是配置 URI 后立即同步播放。

   tizen_src/chromium_impl/media/filters/media_player_bridge_capi.cc:348

   346:   LOG_ID(INFO, player_id_) << "Call player_prepare_async";
   347: 
   348:   int ret = player_prepare_async(player_, PlayerPreparedCb, this);
   349:   if (ret != PLAYER_ERROR_NONE) {
   350:     is_preparing_ = false;
   351:     OnHandlePlayerError(ret, FROM_HERE);
   352:     return false;
   353:   }
   354: 
   355:   is_preparing_ = true;
   356:   return true;

8. 平台 API / 播放MediaPlayerBridgeCapi::Play() → player_start()

   在准备、状态与播放请求满足条件时启动平台播放。

   tizen_src/chromium_impl/media/filters/media_player_bridge_capi.cc:488

   486: }
   487: 
   488: bool MediaPlayerBridgeCapi::Play() {
   489:   LOG_ID(INFO, player_id_) << "(" << static_cast<void*>(this) << ") "
   490:                            << __func__;
   491: 
   492:   if (IsPlayerSuspended()) {
   493:     LOG(INFO) << "(" << static_cast<void*>(this) << ") " << __func__
   494:               << " Player is suspended...";
   495:     is_play_pending_ = true;
   496:     delayed_player_state_ = PLAYER_STATE_DELAYED_PLAY;

此链在 renderer 处理分片并形成压缩样本。HEVC 是 codec 条件分支，不代表所有 MSE 内容都经过 HEVC。

1. JS / BlinkSourceBuffer.appendBuffer() → AppendBufferInternal()

   检查追加状态并接收 JS 提供的媒体字节。

   third_party/blink/renderer/modules/mediasource/source_buffer.cc:602

   600: }
   601: 
   602: void SourceBuffer::appendBuffer(DOMArrayBuffer* data,
   603:                                 ExceptionState& exception_state) {
   604:   DVLOG(2) << __func__ << " this=" << this << " size=" << data->ByteLength();
   605:   // Section 3.2 appendBuffer()
   606:   // https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html#widl-SourceBuffer-appendBuffer-void-ArrayBufferView-data
   607:   AppendBufferInternal(data->ByteSpan(), exception_state);
   608: }
   609: 
   610: void SourceBuffer::appendBuffer(NotShared<DOMArrayBufferView> data,

2. 字节缓存WebSourceBufferImpl::AppendToParseBuffer()

   先把追加字节交给 ChunkDemuxer 的解析缓冲。

   third_party/blink/renderer/platform/media/web_source_buffer_impl.cc:137

   135: }
   136: 
   137: bool WebSourceBufferImpl::AppendToParseBuffer(
   138:     base::span<const unsigned char> data) {
   139:   return demuxer_->AppendToParseBuffer(id_, data);
   140: }
   141: 
   142: media::StreamParser::ParseStatus WebSourceBufferImpl::RunSegmentParserLoop(
   143:     double* timestamp_offset) {
   144:   base::TimeDelta old_offset = timestamp_offset_;
   145:   media::StreamParser::ParseStatus parse_result =

3. 任务边界 / 异步SourceBuffer::AppendBufferAsyncPart_Locked()

   排队任务运行 segment parser loop；可能分多轮处理。

   third_party/blink/renderer/modules/mediasource/source_buffer.cc:2130

   2128: }
   2129: 
   2130: void SourceBuffer::AppendBufferAsyncPart_Locked(
   2131:     MediaSourceAttachmentSupplement::ExclusiveKey pass_key) {
   2132:   DCHECK(source_);
   2133:   source_->AssertAttachmentsMutexHeldIfCrossThreadForDebugging();
   2134:   DCHECK(updating_);
   2135: 
   2136:   // Section 3.5.4 Buffer Append Algorithm
   2137:   // https://dvcs.w3.org/hg/html-media/raw-file/default/media-source/media-source.html#sourcebuffer-buffer-append
   2138: 

4. 分片解析WebSourceBufferImpl::RunSegmentParserLoop() → ChunkDemuxer::RunSegmentParserLoop()

   把 append window 与 timestamp offset 交给 demuxer。

   third_party/blink/renderer/platform/media/web_source_buffer_impl.cc:142

   140: }
   141: 
   142: media::StreamParser::ParseStatus WebSourceBufferImpl::RunSegmentParserLoop(
   143:     double* timestamp_offset) {
   144:   base::TimeDelta old_offset = timestamp_offset_;
   145:   media::StreamParser::ParseStatus parse_result =
   146:       demuxer_->RunSegmentParserLoop(id_, append_window_start_,
   147:                                      append_window_end_, &timestamp_offset_);
   148: 
   149:   // Coded frame processing may update the timestamp offset. If the caller
   150:   // provides a non-nullptr |timestamp_offset| and frame processing changes the

5. 容器解析 / MP4 条件SourceBufferState::RunSegmentParserLoop() → MP4StreamParser::Parse()

   MP4 parser 分析 box、track run 与媒体样本。

   media/filters/source_buffer_state.cc:234

   232:   // and timestamp offset pointer. See http://crbug.com/351454.
   233:   StreamParser::ParseStatus result =
   234:       stream_parser_->Parse(StreamParser::kMaxPendingBytesPerParse);
   235: 
   236:   if (result == StreamParser::ParseStatus::kFailed) {
   237:     MEDIA_LOG(ERROR, media_log_)
   238:         << __func__ << ": stream parsing failed. append_window_start="
   239:         << append_window_start.InSecondsF()
   240:         << " append_window_end=" << append_window_end.InSecondsF();
   241:   }
   242: 

6. 样本准备MP4StreamParser::EnqueueSample() → TrackRunIterator::GetDecryptConfig()

   加密样本取得 KID / IV / subsamples；样本输出阶段附加时间戳与配置。

   media/formats/mp4/mp4_stream_parser.cc:1248

   1246:   std::vector<SubsampleEntry> subsamples;
   1247:   if (runs_->is_encrypted()) {
   1248:     decrypt_config = runs_->GetDecryptConfig();
   1249:     if (!decrypt_config)
   1250:       return ParseResult::kError;
   1251:     subsamples = decrypt_config->subsamples();
   1252:   }
   1253: 
   1254:   // This may change if analysis results indicate runs_->is_keyframe() is
   1255:   // opposite of what the coded frame contains.
   1256:   bool is_keyframe = runs_->is_keyframe();

7. HEVC 条件分支HEVCBitstreamConverter::ConvertAndAnalyzeFrame()

   长度前缀转 Annex B，分析关键帧并按需插入参数集；同步维护 subsamples。

   media/formats/mp4/hevc.cc:649

   647: }
   648: 
   649: bool HEVCBitstreamConverter::ConvertAndAnalyzeFrame(
   650:     std::vector<uint8_t>* frame_buf,
   651:     bool is_keyframe,
   652:     std::vector<SubsampleEntry>* subsamples,
   653:     AnalysisResult* analysis_result) const {
   654:   RCHECK(AVC::ConvertFrameToAnnexB(hevc_config_->lengthSizeMinusOne + 1,
   655:                                    frame_buf, subsamples));
   656:   // |is_keyframe| may be incorrect. Analyze the frame to see if it is a
   657:   // keyframe. |is_keyframe| will be used if the analysis is inconclusive.

8. NAL 解析HEVC::AnalyzeAnnexB() / InsertParamSetsAnnexB() → H265NaluParser

   分析与参数集插入路径调用 NAL parser，属于解密前的码流结构处理。

   media/formats/mp4/hevc.cc:461

   459:   // units
   460:   while (true) {
   461:     H265NaluParser::Result h265_result = parser.AdvanceToNextNALU(&nalu);
   462:     if (h265_result == H265NaluParser::kEOStream) {
   463:       break;
   464:     }
   465: 
   466:     if (h265_result != H265NaluParser::kOk) {
   467:       DCHECK_NE(h265_result, H265NaluParser::kUnsupportedStream)
   468:           << "AdvanceToNextNALU() returned kUnsupportedStream!";
   469:       return result;

9. codec parserH265NaluParser::AdvanceToNextNALU()

   读取 NAL 头；此快照中的具体检查以代码片段为准，不套用 M94 或历史故障提交。

   media/parsers/h265_nalu_parser.cc:128

   126: }
   127: 
   128: H265NaluParser::Result H265NaluParser::AdvanceToNextNALU(H265NALU* nalu) {
   129:   off_t start_code_size;
   130:   off_t nalu_size_with_start_code;
   131:   if (!LocateNALU(&nalu_size_with_start_code, &start_code_size)) {
   132:     DVLOG(4) << "Could not find next NALU, bytes left in stream: "
   133:              << bytes_left_;
   134:     return kEOStream;
   135:   }
   136: 

10. 缓冲交接MP4StreamParser → StreamParserBuffer / buffers

    形成带压缩样本和元数据的输出，交给后续缓冲及异步读取；append 不直接调用平台 submit。

    media/formats/mp4/mp4_stream_parser.cc:1410

    1408: 
    1409:   if (decrypt_config)
    1410:     stream_buf->set_decrypt_config(std::move(decrypt_config));
    1411: 
    1412:   if (runs_->duration() != kNoTimestamp) {
    1413:     stream_buf->set_duration(runs_->duration());
    1414:   } else {
    1415:     MEDIA_LOG(ERROR, media_log_) << "Frame duration exceeds representable "
    1416:                                  << "limit";
    1417:     return ParseResult::kError;
    1418:   }

读取方向为 browser → renderer，数据回传方向相反；异步回调后才进入平台样本队列。

1. 预先绑定 streamsMojoRenderer::InitializeRendererFromStreams()

   renderer 将本地 DemuxerStream 暴露为 Mojo 接口。

   media/mojo/clients/mojo_renderer.cc:85

   83:   for (media::DemuxerStream* stream : streams) {
   84:     mojo::PendingRemote<mojom::DemuxerStream> stream_proxy;
   85:     auto mojo_stream = std::make_unique<MojoDemuxerStreamImpl>(
   86:         stream, stream_proxy.InitWithNewPipeAndPassReceiver());
   87: 
   88:     // Using base::Unretained(this) is safe because |this| owns |mojo_stream|,
   89:     // and the error handler can't be invoked once |mojo_stream| is destroyed.
   90:     mojo_stream->set_disconnect_handler(
   91:         base::BindOnce(&MojoRenderer::OnDemuxerStreamConnectionError,
   92:                        base::Unretained(this), mojo_stream.get()));
   93: 

2. browser 适配MediaResourceShim → MojoDemuxerStreamAdapter

   browser 把远程 streams 包装为本地可读的 DemuxerStream。

   media/mojo/services/media_resource_shim.cc:23

   21: 
   22:   for (auto& s : streams) {
   23:     streams_.emplace_back(std::make_unique<MojoDemuxerStreamAdapter>(
   24:         std::move(s), base::BindOnce(&MediaResourceShim::OnStreamReady,
   25:                                      weak_factory_.GetWeakPtr())));
   26:   }
   27: }
   28: 
   29: MediaResourceShim::~MediaResourceShim() = default;
   30: 
   31: std::vector<DemuxerStream*> MediaResourceShim::GetAllStreams() {

3. 平台流播放器MediaPlayerRegistry → MediaPlayerESPlusPlayerFactory::Create()

   kStream 资源选择 ESPlusPlayer，TV 构建创建 TV 子类。

   tizen_src/chromium_impl/media/filters/media_player_esplusplayer_factory.cc:21

   19:     double volume) {
   20: #if BUILDFLAG(IS_TIZEN_TV)
   21:   return std::make_unique<MediaPlayerESPlusPlayerTV>();
   22: #else
   23:   return std::make_unique<MediaPlayerESPlusPlayerCommon>();
   24: #endif
   25: }
   26: 
   27: }  // namespace media

4. browser 拉取MediaPlayerESPlusPlayer::ReadBuffer()

   先消耗已有队列；检查背压、暂停、EOS 和 pending read，再请求一批样本。

   tizen_src/chromium_impl/media/filters/media_player_esplusplayer.cc:998

   996: }
   997: 
   998: void MediaPlayerESPlusPlayer::ReadBuffer(DemuxerStream::Type type) {
   999:   if (!ReadFromBufferQueue(type))
   1000:     return;
   1001: 
   1002:   // Avoid unnecessary or redundant read requests.
   1003:   if (!ShouldFeed(type) || ReadRequested(type) || IsEos(type) ||
   1004:       (is_prepared_ && is_paused_ && !is_seeking_)) {
   1005:     return;
   1006:   }

5. Mojo IPC / 请求MojoDemuxerStreamAdapter::Read() ⇢ MojoDemuxerStreamImpl::Read()

   读取请求通过 Mojo 发往 renderer 的 stream 实现。

   media/mojo/services/mojo_demuxer_stream_adapter.cc:43

   41: 
   42:   read_cb_ = std::move(read_cb);
   43:   demuxer_stream_->Read(count,
   44:                         base::BindOnce(&MojoDemuxerStreamAdapter::OnBufferReady,
   45:                                        weak_factory_.GetWeakPtr()));
   46: }
   47: 
   48: AudioDecoderConfig MojoDemuxerStreamAdapter::audio_decoder_config() {
   49:   DCHECK_EQ(type_, AUDIO);
   50:   return audio_config_;
   51: }

6. renderer / 异步回调MojoDemuxerStreamImpl::Read() → stream_->Read()

   异步读取本地压缩样本，并在 OnBufferReady 中序列化返回。

   media/mojo/clients/mojo_demuxer_stream_impl.cc:55

   53: }
   54: 
   55: void MojoDemuxerStreamImpl::Read(uint32_t count, ReadCallback callback) {
   56:   DVLOG(3) << __func__ << ": count=" << count;
   57:   stream_->Read(
   58:       count, base::BindOnce(&MojoDemuxerStreamImpl::OnBufferReady,
   59:                             weak_factory_.GetWeakPtr(), std::move(callback)));
   60: }
   61: 
   62: void MojoDemuxerStreamImpl::EnableBitstreamConverter() {
   63:   stream_->EnableBitstreamConverter();

7. Mojo 数据返回MojoDemuxerStreamAdapter::OnBufferReady() → OnBufferRead()

   通过 buffer reader 还原数据；回调完成后向平台读取者交付 buffer。

   media/mojo/services/mojo_demuxer_stream_adapter.cc:134

   132: 
   133:   batch_buffers_ = std::move(batch_buffers);
   134:   mojo_decoder_buffer_reader_->ReadDecoderBuffer(
   135:       std::move(batch_buffers_[0]),
   136:       base::BindOnce(&MojoDemuxerStreamAdapter::OnBufferRead,
   137:                      weak_factory_.GetWeakPtr()));
   138: }
   139: 
   140: void MojoDemuxerStreamAdapter::OnBufferRead(
   141:     scoped_refptr<DecoderBuffer> buffer) {
   142:   if (!buffer) {

8. browser 回调MediaPlayerESPlusPlayer::OnBufferReady() → ReadBuffer()

   检查状态与 flush generation，将有效样本放入队列后继续喂入。

   tizen_src/chromium_impl/media/filters/media_player_esplusplayer.cc:1046

   1044: }
   1045: 
   1046: void MediaPlayerESPlusPlayer::OnBufferReady(
   1047:     uint64_t posted_flush_id,
   1048:     DemuxerStream::Type type,
   1049:     DemuxerStream::Status status,
   1050:     DemuxerStream::DecoderBufferVector buffers) {
   1051:   // Defensive check: drop buffers if player has been released.
   1052:   // After Release(), esplayer_ handle is closed and player state is cleaned up.
   1053:   // OnBufferReady may still be called by pending DemuxerStream::Read() callbacks.
   1054:   if (IsReleased()) {

9. 背压 / 平台提交MediaPlayerESPlusPlayer::ReadFromBufferQueue() → SubmitEsPacket()

   提交队首样本；FULL / NOT_PREPARED 等状态保留队列并停止继续喂入。

   tizen_src/chromium_impl/media/filters/media_player_esplusplayer.cc:1118

   1116:     status = SubmitEosPacket(type);
   1117:   else
   1118:     status = SubmitEsPacket(type, buffer);
   1119: 
   1120:   if (status == ESPLUSPLAYER_SUBMIT_STATUS_FULL) {
   1121:     return false;
   1122:   }
   1123: 
   1124:   if ((status == ESPLUSPLAYER_SUBMIT_STATUS_NOT_PREPARED) ||
   1125:       (status == ESPLUSPLAYER_SUBMIT_STATUS_OUT_OF_MEMORY))
   1126:     return false;

10. 平台 API 边界MediaPlayerESPlusPlayerTV::SubmitEsPacket()

    按 DRM / handle 分支提交 encrypted packet、trust-zone packet，或调用普通父类提交。

    tizen_src/chromium_impl/media/filters/media_player_esplusplayer_tv.cc:644

    642: }
    643: 
    644: esplusplayer_submit_status MediaPlayerESPlusPlayerTV::SubmitEsPacket(
    645:     DemuxerStream::Type type,
    646:     scoped_refptr<DecoderBuffer> buffer) {
    647:   // Defensive check: prevent submitting packets after Release() has been called.
    648:   // This guards against race conditions where OnBufferReady may still execute
    649:   // after the player has been released and esplayer_ handle has been closed.
    650:   if (IsReleased()) {
    651:     LOG_ID(WARNING, player_id_)
    652:         << "Player is released, skip submit "