ExoPlayer 多路流切换

 val mediaDataSourceFactory: DataSource.Factory = DefaultDataSource.Factory(this)        var array = ArrayList<MediaItem>()        var mediaSources = ArrayList<MediaSource>()        //加入480资源，包含音频和视频Track        array.add(MediaItem.fromUri("asset://android_asset/viNM94G2aJw000_G/Video@MV@480/data"))        //加入1080，包含音频和视频Track        array.add(MediaItem.fromUri("asset://android_asset/viNM94G2aJw000_G/Video@MV@1080/data"))        //再加入2组音频，可以实现音频切换效果，下面的ACC是高品质伴奏        array.add(MediaItem.fromUri("asset://android_asset/viNM94G2aJw000_G/Audio@ACC@Q_1/data"))        //加入原唱        array.add(MediaItem.fromUri("asset://android_asset/viNM94G2aJw000_G/Audio@ORI@Q_1/data"))        val mediaSourceFactory = DefaultMediaSourceFactory(mediaDataSourceFactory)        array.forEach {            mediaSources.add(mediaSourceFactory.createMediaSource(it))        }        var targetMergingMediaSource = MergingMediaSource(mediaSources[0],mediaSources[1],mediaSources[2])

public static void switchToOtherVideoTrack(ExoPlayer exoPlayer, @NotNull Tracks tracks, int width, int heigth) {        if (tracks == null || exoPlayer == null) return;        ImmutableList<Tracks.Group> groups = tracks.getGroups();        for (Tracks.Group group :                groups) {            if (group == null) continue;            if (group.getType() != C.TRACK_TYPE_VIDEO) {                continue; //非视频的不切换            }            boolean selected = group.isSelected();            if (selected) {                continue; //当前播的不切换            }            for (int trackIndex = 0; trackIndex < group.length; trackIndex++) {            //获取一种匹配的视频，理论上group.length一般是1                Format trackFormat = group.getTrackFormat(trackIndex);                if (trackFormat.width != width || trackFormat.height != heigth) {                    continue;                }                TrackSelectionParameters trackSelectionParameters = exoPlayer.getTrackSelectionParameters();                TrackSelectionParameters selectionParameters = trackSelectionParameters                        .buildUpon()                        .setOverrideForType(                                new TrackSelectionOverride(                                        group.getMediaTrackGroup(), ImmutableList.of(trackIndex) //设置目标媒体资源组和目标Track索引                                )                        )                        .setTrackTypeDisabled(group.getType(), /* disabled= */ false) //保证改Track不被关闭                        .build();                exoPlayer.setTrackSelectionParameters(selectionParameters);                Log.d("SelectTrackHelper", "--->group :" + group + ", selected=" + selected + ",group=" + group.getType() + "," + trackFormat);            }        }    }

SelectTrackHelper.switchToOtherVideoTrack(simpleExoPlayer,simpleExoPlayer.currentTracks,848,476)

 private void reselectTracksInternal() throws ExoPlaybackException {    float playbackSpeed = mediaClock.getPlaybackParameters().speed;    // Reselect tracks on each period in turn, until the selection changes.    MediaPeriodHolder periodHolder = queue.getPlayingPeriod();    MediaPeriodHolder readingPeriodHolder = queue.getReadingPeriod();    boolean selectionsChangedForReadPeriod = true;    TrackSelectorResult newTrackSelectorResult;    //查找匹配当前参数的periodHolder    while (true) {      if (periodHolder == null || !periodHolder.prepared) {        // The reselection did not change any prepared periods.        return;      }     //这里是重点，会调用到MappingTrackSelector#selectTracks方法，返回新的结果      newTrackSelectorResult = periodHolder.selectTracks(playbackSpeed, playbackInfo.timeline);      if (!newTrackSelectorResult.isEquivalent(periodHolder.getTrackSelectorResult())) {        // Selected tracks have changed for this period.       //判断新的结果和当前是不是一样，一样的话重新选择，不一样说明选择成功        break;      }      if (periodHolder == readingPeriodHolder) {        // The track reselection didn't affect any period that has been read.        selectionsChangedForReadPeriod = false;      }      periodHolder = periodHolder.getNext();    }    //重建流数组，如果匹配的解码位置比较靠前的话    if (selectionsChangedForReadPeriod) {      // Update streams and rebuffer for the new selection, recreating all streams if reading ahead.      MediaPeriodHolder playingPeriodHolder = queue.getPlayingPeriod();      boolean recreateStreams = queue.removeAfter(playingPeriodHolder);      boolean[] streamResetFlags = new boolean[renderers.length];      long periodPositionUs =          playingPeriodHolder.applyTrackSelection(              newTrackSelectorResult, playbackInfo.positionUs, recreateStreams, streamResetFlags);      playbackInfo =          handlePositionDiscontinuity(              playbackInfo.periodId, periodPositionUs, playbackInfo.requestedContentPositionUs);      if (playbackInfo.playbackState != Player.STATE_ENDED          && periodPositionUs != playbackInfo.positionUs) {        playbackInfoUpdate.setPositionDiscontinuity(Player.DISCONTINUITY_REASON_INTERNAL);        resetRendererPosition(periodPositionUs);      }     //按照Renders顺序，分别对比每个Renderer和每个SampleStream，判断当前正在使用的渲染器Track流是否匹配     //注意：这里是循环，说明我们切换多路流时可以同时切换音频和视频等轨道      boolean[] rendererWasEnabledFlags = new boolean[renderers.length];      for (int i = 0; i < renderers.length; i++) {        Renderer renderer = renderers[i];        //获取第i轨道正在使用的渲染器，注意这里是可以渲染        rendererWasEnabledFlags[i] = isRendererEnabled(renderer);          //获取第i轨道当前正在使用的SampleStream        SampleStream sampleStream = playingPeriodHolder.sampleStreams[i];         //当前渲染器正在使用才会被检测        if (rendererWasEnabledFlags[i]) {           if (sampleStream != renderer.getStream()) {            // We need to disable the renderer.           //如果当前渲染器的码流和目标码流不匹配，则关闭当前渲染器            disableRenderer(renderer);           } else if (streamResetFlags[i]) {            // The renderer will continue to consume from its current stream, but needs to be reset.            renderer.resetPosition(rendererPositionUs);//如果码流匹配，统一同步播放位置          }        }      }//重新创建被关闭的渲染器      enableRenderers(rendererWasEnabledFlags);    } else {//如果还没播放，则直接走启动逻辑      // Release and re-prepare/buffer periods after the one whose selection changed.      queue.removeAfter(periodHolder);      if (periodHolder.prepared) {        long loadingPeriodPositionUs =            max(periodHolder.info.startPositionUs, periodHolder.toPeriodTime(rendererPositionUs));        periodHolder.applyTrackSelection(newTrackSelectorResult, loadingPeriodPositionUs, false);      }    }    handleLoadingMediaPeriodChanged(/* loadingTrackSelectionChanged= */ true);    if (playbackInfo.playbackState != Player.STATE_ENDED) {      //这里会通过开始时间，查询SeekPoint，设置采样队列时间界值      maybeContinueLoading();      updatePlaybackPositions();      handler.sendEmptyMessage(MSG_DO_SOME_WORK);    }  }

loadable.setLoadPosition(    checkNotNull(seekMap).getSeekPoints(pendingResetPositionUs).first.position,    pendingResetPositionUs);

 for (SampleQueue sampleQueue : sampleQueues) {        sampleQueue.setStartTimeUs(pendingResetPositionUs);    }

if (buffer.timeUs < startTimeUs) {//这里对inputBuffer添加标记  buffer.addFlag(C.BUFFER_FLAG_DECODE_ONLY); }

if (isDecodeOnlyBuffer && !isLastBuffer) {  skipOutputBuffer(codec, bufferIndex, presentationTimeUs);  return true;}

   public void render(long positionUs, long elapsedRealtimeUs) throws ExoPlaybackException {      if (bypassEnabled) {        TraceUtil.beginSection("bypassRender");        while (bypassRender(positionUs, elapsedRealtimeUs)) {}        TraceUtil.endSection();      } else if (codec != null) {        long renderStartTimeMs = SystemClock.elapsedRealtime();        TraceUtil.beginSection("drainAndFeed");        //消费InputBuffer数据        while (drainOutputBuffer(positionUs, elapsedRealtimeUs)            && shouldContinueRendering(renderStartTimeMs)) {}            //读取InputBuffer数据        while (feedInputBuffer() && shouldContinueRendering(renderStartTimeMs)) {}        TraceUtil.endSection();      } else {        decoderCounters.skippedInputBufferCount += skipSource(positionUs);        // We need to read any format changes despite not having a codec so that drmSession can be        // updated, and so that we have the most recent format should the codec be initialized. We        // may also reach the end of the stream. Note that readSource will not read a sample into a        // flags-only buffer.        readToFlagsOnlyBuffer(/* requireFormat= */ false);      }      decoderCounters.ensureUpdated();  }

  boolean treatDroppedBuffersAsSkipped = joiningDeadlineMs != C.TIME_UNSET;    if (shouldDropBuffersToKeyframe(earlyUs, elapsedRealtimeUs, isLastBuffer)        && maybeDropBuffersToKeyframe(            codec, bufferIndex, presentationTimeUs, positionUs, treatDroppedBuffersAsSkipped)) {      return false;    } else if (shouldDropOutputBuffer(earlyUs, elapsedRealtimeUs, isLastBuffer)) {      if (treatDroppedBuffersAsSkipped) {        skipOutputBuffer(codec, bufferIndex, presentationTimeUs);      } else {        dropOutputBuffer(codec, bufferIndex, presentationTimeUs);      }      updateVideoFrameProcessingOffsetCounters(earlyUs);      return true;    }