ExoPlayer 2 的质量选择器

Posted 2023-04-15

【中文标题】ExoPlayer 2 的质量选择器

【英文标题】：Quality selector for ExoPlayer 2

【发布时间】：2018-01-31 19:09:34

【问题描述】：

我目前正在开发一个直播和电影播放器​​应用程序。我选择了ExoPlayer version 2来播放这部电影，我对它了解不多。我想让用户在播放器屏幕上选择电影的质量，例如，720p 或 1080p 等。 但我不知道如何获取现有品质的列表并将其展示给用户。 下面的代码是我对 SimpleExoPlayer 的实现：

private void initPlayer(String path)
    Handler handler = new Handler();
    // 1. Create a default TrackSelector
    BandwidthMeter bandwidthMeter = new DefaultBandwidthMeter();
    TrackSelection.Factory videoTrackSelectionFactory =
            new AdaptiveVideoTrackSelection.Factory(bandwidthMeter);
    TrackSelector trackSelector =
            new DefaultTrackSelector(videoTrackSelectionFactory);

    // 2. Create a default LoadControl
    LoadControl loadControl = new DefaultLoadControl();
    // 3. Create the player
    player = ExoPlayerFactory.newSimpleInstance(this, trackSelector, loadControl);

    SimpleExoPlayerView playerView = (SimpleExoPlayerView) findViewById(R.id.player_view);
    playerView.setPlayer(player);
    playerView.setKeepScreenOn(true);
    // Produces DataSource instances through which media data is loaded.
    DataSource.Factory dataSourceFactory = new DefaultDataSourceFactory(this, Util.getUserAgent(this, "ExoPlayer"));

    // This is the MediaSource representing the media to be played.
    MediaSource videoSource = new HlsMediaSource(Uri.parse(path),
            dataSourceFactory,handler, null);
    // Prepare the player with the source.
    player.addListener(this);
    player.prepare(videoSource);
    playerView.requestFocus();
    player.setPlayWhenReady(true); // to play video when ready. Use false to pause a video


// ExoPlayer Listener Methods :
@Override
public void onTimelineChanged(Timeline timeline, Object manifest) 



@Override
public void onTracksChanged(TrackGroupArray trackGroups, TrackSelectionArray trackSelections) 



@Override
public void onLoadingChanged(boolean isLoading) 



@Override
public void onPlayerStateChanged(boolean playWhenReady, int playbackState) 
    switch (playbackState) 
        case ExoPlayer.STATE_BUFFERING:
            //You can use progress dialog to show user that video is preparing or buffering so please wait
            progressBar.setVisibility(View.VISIBLE);
            break;
        case ExoPlayer.STATE_IDLE:
            //idle state
            break;
        case ExoPlayer.STATE_READY:
            // dismiss your dialog here because our video is ready to play now
            progressBar.setVisibility(GONE);
            //Toast.makeText(getApplicationContext(),String.valueOf(player.getCurrentTrackSelections().get(0).getSelectedFormat().bitrate),Toast.LENGTH_SHORT).show();
            break;
        case ExoPlayer.STATE_ENDED:
            // do your processing after ending of video
            break;
    


@Override
public void onPlayerError(ExoPlaybackException error) 
    // show user that something went wrong. it can be a dialog


@Override
public void onPositionDiscontinuity() 

请帮助解决这个问题。 非常感谢。

【参考方案1】：

您想要实现的一切都可以在 ExoPlayer2 demo app 中查看。更具体地说是PlayerActivity 类。

您也可以查看此good article 的主题。

您要研究的核心点是围绕曲目选择（通过TrackSelector）以及TrackSelectionHelper。我将在下面包含重要的代码示例，希望它们足以让您继续前进。但最终，只要在演示应用中遵循类似的内容，您就可以到达您需要的地方。

您将按住用于初始化播放器的轨道选择器，并将其用于几乎所有事情。

以下只是一段代码，可以理想地涵盖您正在尝试做的事情的要点，因为该演示确实使事情变得过于复杂。另外我还没有运行代码，但它已经足够接近了。

// These two could be fields OR passed around
int videoRendererIndex;
TrackGroupArray trackGroups;

// This is the body of the logic for see if there are even video tracks
// It also does some field setting
MappedTrackInfo mappedTrackInfo = trackSelector.getCurrentMappedTrackInfo();
for (int i = 0; i < mappedTrackInfo.length; i++) 
  TrackGroupArray trackGroups = mappedTrackInfo.getTrackGroups(i);
  if (trackGroups.length != 0) 
    switch (player.getRendererType(i)) 
      case C.TRACK_TYPE_VIDEO:
        videoRendererIndex = i;
        return true;
    
  


// This next part is actually about getting the list. It doesn't include
// some additional logic they put in for adaptive tracks (DASH/HLS/SS),
// but you can look at the sample for that (TrackSelectionHelper#buildView())
// Below you'd be building up items in a list. This just does
// views directly, but you could just have a list of track names (with indexes)
for (int groupIndex = 0; groupIndex < trackGroups.length; groupIndex++) 
  TrackGroup group = trackGroups.get(groupIndex);
  for (int trackIndex = 0; trackIndex < group.length; trackIndex++) 
    if (trackIndex == 0) 
      // Beginning of a new set, the demo app adds a divider
    
    CheckedTextView trackView = ...; // The TextView to show in the list
    // The below points to a util which extracts the quality from the TrackGroup
    trackView.setText(DemoUtil.buildTrackName(group.getFormat(trackIndex)));


// Assuming you tagged the view with the groupIndex and trackIndex, you
// can build your override with that info.
Pair<Integer, Integer> tag = (Pair<Integer, Integer>) view.getTag();
int groupIndex = tag.first;
int trackIndex = tag.second;
// This is the override you'd use for something that isn't adaptive.
override = new SelectionOverride(FIXED_FACTORY, groupIndex, trackIndex);
// Otherwise they call their helper for adaptives, which roughly does:
int[] tracks = getTracksAdding(override, trackIndex);
TrackSelection.Factory factory = tracks.length == 1 ? FIXED_FACTORY : adaptiveTrackSelectionFactory;
override = new SelectionOverride(factory, groupIndex, tracks);

// Then we actually set our override on the selector to switch the quality/track
selector.setSelectionOverride(rendererIndex, trackGroups, override);

正如我上面提到的，这有点过于简单化了这个过程，但核心部分是你在搞乱TrackSelector、SelectionOverride和Track/TrackGroups来得到这个工作。

您可以想象逐字复制演示代码，它应该可以工作，但我强烈建议您花时间了解每个部分在做什么，并根据您的用例定制您的解决方案。

如果我有更多时间，我会编译并运行它。但是，如果您可以获取我的示例，请随时编辑我的帖子。

希望有帮助:)

【讨论】：

@KyleVenn 你能告诉我更多关于这一点，比如如果轨道包含 240p 质量，它将通过添加上述代码自动显示？

@WaleedAsim 有一个 for 循环遍历轨道索引。 240p 将是可用的质量之一。所以在group.getFormat(trackIndex) 行中，240p 将由组中的一种格式表示。上面的代码只是关于如何遍历格式，然后通过“覆盖”强制格式。

@KyleVenn 你能告诉我如何在安卓存储中下载 hls 格式的视频

@WaleedAsim 这篇文章介绍了如何通过CacheDataSource：medium.com/google-exoplayer/downloading-streams-6d259eec7f95实现这一目标

@Kyle Venn 如果可能，请您提供完整代码

【参考方案2】：

我避免使用上面发布的方式。我的方式是使用 DefaultTrackSelector 如下：

trackSelector.setParameters(trackSelector.getParameters()
                          .withMaxVideoBitrate(bitrate)
                          .withMaxVideoSize(width, height));

我已经使用 HLS 视频进行了测试，它似乎以正确的方式执行。我从 HlsManifest 中读取比特率、宽度和高度。

【参考方案3】：

您可以从此链接复制示例代码。 ExoPlayer Video Quality Control.

注意：不要忘记在 build.gradle 文件中添加 exoplayer 依赖项

implementation 'com.google.android.exoplayer:exoplayer-core:2.16.1'
implementation 'com.google.android.exoplayer:exoplayer-dash:2.16.1'
implementation 'com.google.android.exoplayer:exoplayer-ui:2.16.1'
implementation 'com.google.android.exoplayer:exoplayer:2.16.1'