带起始曲目的短跑自适应播放，如何？

Question

我有 3 种方式在我的应用程序中播放自适应破折号视频：

固定视频和音频轨道
自适应视频和音频轨道
自适应视频和音频轨道（带起始轨道）

前两种方法非常有效，但是第三种方法表现得很奇怪。

我所做的是首先在 'onTracksChanged' 方法上设置起始曲目。一旦播放器调用 onLoadingChanged(false) 方法，我想删除起始轨道的 selection 并让播放器 select 最佳轨道。为了删除 selected，我调用了 trackSelector.clearSelectionOverrides()，但这完全删除了缓冲区，视频停止并开始在最佳轨道中缓冲。

我想要实现的行为如下:

select startt tracks (假设是 144p) -> 加载第一个块 -> 删除 144p 的 selection -> 继续以 144p 播放剩余的缓冲区并开始以最佳方式加载同时跟踪。

如何实现？

Answer 1

您可以使用 AdaptiveTrackSelection 执行此操作，并将除您想要保留的曲目之外的所有曲目列入黑名单。要实现这一点，提供您自己的 TrackSelection.Factory.

似乎最简单

public class StartupTrackSelectionFactory implements TrackSelection.Factory {

  // end blacklisting after ten seconds earliest
  private static final long BLACKLIST_DURATION = 10 * 1000;

  private final BandwidthMeter bandwidthMeter;

  public StartupTrackSelectionFactory(BandwidthMeter bandwidthMeter) {
    this.bandwidthMeter = bandwidthMeter;
  }

  @Override
  public TrackSelection createTrackSelection(TrackGroup group, int... tracks) {
    AdaptiveTrackSelection adaptiveTrackSelection = new AdaptiveTrackSelection(
        group,
        tracks,
        bandwidthMeter,
        AdaptiveTrackSelection.DEFAULT_MAX_INITIAL_BITRATE,
        AdaptiveTrackSelection.DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS,
        AdaptiveTrackSelection.DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS,
        AdaptiveTrackSelection.DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS,
        AdaptiveTrackSelection.DEFAULT_BANDWIDTH_FRACTION,
        AdaptiveTrackSelection.DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE,
        AdaptiveTrackSelection.DEFAULT_MIN_TIME_BETWEEN_BUFFER_REEVALUTATION_MS,
        Clock.DEFAULT);

    int lowestBitrate = Integer.MAX_VALUE;
    int lowestBitrateTrackIndex = C.INDEX_UNSET;
    for (int i = 0; i < tracks.length; i++) {
      Format format = group.getFormat(tracks[i]);
      if (format.bitrate < lowestBitrate) {
        lowestBitrateTrackIndex = i;
        lowestBitrate = format.bitrate;
      }
      adaptiveTrackSelection.blacklist(tracks[i], BLACKLIST_DURATION);
    }
    if (lowestBitrateTrackIndex != C.INDEX_UNSET) {
      adaptiveTrackSelection.blacklist(tracks[lowestBitrateTrackIndex], 0);
    }
    return adaptiveTrackSelection;
  }

}

现在，在创建 DefaultTrackSelector 时，您可以传递 StartupTrackSelectionFactory 并使用它来创建播放器实例。

TrackSelection.Factory trackSelectionFactory = 
          new StartupTrackSelectionFactory(BANDWIDTH_METER);
trackSelector = new DefaultTrackSelector(trackSelectionFactory);
player = ExoPlayerFactory.newSimpleInstance(renderersFactory, trackSelector);

如果您想保持监听 onLoadChange 事件的方法，您可能希望最初将 Long.MAX_VALUE 作为黑名单持续时间，然后在调用 onLoadChange 时将所有索引的持续时间设置为 0。

Answer 2

由于 createTrackSelection 方法已从库中删除，我们现在可以直接实现 AdaptiveTrackSelection.Factory() 并覆盖它的 createAdaptiveTrackSelection 方法并使用@marcbaechinger 的代码。下面是它的 kotlin 版本。

class SmoothTrackSelectionFactory(bandwidthMeter: DefaultBandwidthMeter) : AdaptiveTrackSelection.Factory() {

    // end blacklisting after ten seconds earliest
    private val BLACKLIST_DURATION = (10 * 1000).toLong()

    private var bandwidthMeter: BandwidthMeter = bandwidthMeter

    override fun createAdaptiveTrackSelection(group: TrackGroup, bandwidthMeter: BandwidthMeter, tracks: IntArray, totalFixedTrackBandwidth: Int): AdaptiveTrackSelection {
        val adaptiveTrackSelection = AdaptiveTrackSelection(
                group,
                tracks,
                bandwidthMeter,
                Integer.MAX_VALUE.toLong(),
                AdaptiveTrackSelection.DEFAULT_MIN_DURATION_FOR_QUALITY_INCREASE_MS.toLong(),
                AdaptiveTrackSelection.DEFAULT_MAX_DURATION_FOR_QUALITY_DECREASE_MS.toLong(),
                AdaptiveTrackSelection.DEFAULT_MIN_DURATION_TO_RETAIN_AFTER_DISCARD_MS.toLong(),
                AdaptiveTrackSelection.DEFAULT_BANDWIDTH_FRACTION,
                AdaptiveTrackSelection.DEFAULT_BUFFERED_FRACTION_TO_LIVE_EDGE_FOR_QUALITY_INCREASE,
                AdaptiveTrackSelection.DEFAULT_MIN_TIME_BETWEEN_BUFFER_REEVALUTATION_MS,
                Clock.DEFAULT)
        var lowestBitrate = Int.MAX_VALUE
        var lowestBitrateTrackIndex = C.INDEX_UNSET
        for (i in tracks.indices) {
            val format: Format = group.getFormat(tracks[i])
            if (format.bitrate < lowestBitrate) {
                lowestBitrateTrackIndex = i
                lowestBitrate = format.bitrate
            }
            adaptiveTrackSelection.blacklist(tracks[i], BLACKLIST_DURATION)
        }
        if (lowestBitrateTrackIndex != C.INDEX_UNSET) {
            adaptiveTrackSelection.blacklist(tracks[lowestBitrateTrackIndex], 0)
        }
        return adaptiveTrackSelection
    }
}

带起始曲目的短跑自适应播放，如何？

Dash adaptive playback with starting tracks, How to?

exoplayer

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