android - Exoplayer 自适应 hls 流式传输

Question

我正在寻找如何实现流式传输的良好且简单的示例/ExoPlayer说明HLS Adaptive。我是新手，没有经验和知识，所以我可以从 git 上的代码示例中弄清楚如何做到这一点。

有太多的“移动部件”，所以初学者可以在自己的项目中理解和重用它。

有人可以帮助我学习和理解如何使用/实现ExoPlayer以实现此功能吗？

谢谢！

Answer 1

开始使用 ExoPlayer 的最简单方法是将其添加为 gradle 依赖项。您需要确保在项目根目录的build.gradle文件中包含 jcenter 存储库：

repositories { jcenter() }

接下来，在模块的build.gradle文件中包含以下内容：

compile 'com.google.android.exoplayer:exoplayer:r2.2.0'

1. 你的布局文件

    <?xml version="1.0" encoding="utf-8"?>
<FrameLayout
    android:id="@+id/activity_main"
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.google.android.exoplayer2.ui.SimpleExoPlayerView
        android:id="@+id/player_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:focusable="true"
        app:resize_mode="fill"/>

    <ProgressBar
        android:id="@+id/progressBar"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:visibility="gone"/>

</FrameLayout>

2. 你的类文件（活动）

    public class VideoPlayerActivity extends AppCompatActivity implements ExoPlayer.EventListener {

    private SimpleExoPlayerView simpleExoPlayerView;
    private String hlsVideoUri = "http://playertest.longtailvideo.com/adaptive/bbbfull/bbbfull.m3u8";
    private SimpleExoPlayer player;
    private ProgressBar progressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_video_player);

        // 1. Create a default TrackSelector
        Handler mainHandler = new Handler();
        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 = (SimpleExoPlayerView) findViewById(R.id.player_view);
        simpleExoPlayerView.setPlayer(player);

        // Measures bandwidth during playback. Can be null if not required.
        DefaultBandwidthMeter defaultBandwidthMeter = new DefaultBandwidthMeter();
        // Produces DataSource instances through which media data is loaded.
        DataSource.Factory dataSourceFactory = new DefaultDataSourceFactory(this,
                Util.getUserAgent(this, "Exo2"), defaultBandwidthMeter);
        // Produces Extractor instances for parsing the media data.
        ExtractorsFactory extractorsFactory = new DefaultExtractorsFactory();
        // This is the MediaSource representing the media to be played.
        HlsMediaSource hlsMediaSource = new HlsMediaSource(Uri.parse(hlsVideoUri), dataSourceFactory, mainHandler, new AdaptiveMediaSourceEventListener() {
            @Override
            public void onLoadStarted(DataSpec dataSpec, int dataType, int trackType, Format trackFormat, int trackSelectionReason, Object trackSelectionData, long mediaStartTimeMs, long mediaEndTimeMs, long elapsedRealtimeMs) {

            }

            @Override
            public void onLoadCompleted(DataSpec dataSpec, int dataType, int trackType, Format trackFormat, int trackSelectionReason, Object trackSelectionData, long mediaStartTimeMs, long mediaEndTimeMs, long elapsedRealtimeMs, long loadDurationMs, long bytesLoaded) {

            }

            @Override
            public void onLoadCanceled(DataSpec dataSpec, int dataType, int trackType, Format trackFormat, int trackSelectionReason, Object trackSelectionData, long mediaStartTimeMs, long mediaEndTimeMs, long elapsedRealtimeMs, long loadDurationMs, long bytesLoaded) {

            }

            @Override
            public void onLoadError(DataSpec dataSpec, int dataType, int trackType, Format trackFormat, int trackSelectionReason, Object trackSelectionData, long mediaStartTimeMs, long mediaEndTimeMs, long elapsedRealtimeMs, long loadDurationMs, long bytesLoaded, IOException error, boolean wasCanceled) {

            }

            @Override
            public void onUpstreamDiscarded(int trackType, long mediaStartTimeMs, long mediaEndTimeMs) {

            }

            @Override
            public void onDownstreamFormatChanged(int trackType, Format trackFormat, int trackSelectionReason, Object trackSelectionData, long mediaTimeMs) {

            }
        });

        player.addListener(this);
        player.prepare(hlsMediaSource);
        simpleExoPlayerView.requestFocus();
        player.setPlayWhenReady(true);

        progressBar = (ProgressBar) findViewById(R.id.progressBar);
    }

    @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 Player.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 Player.STATE_IDLE:
                //idle state
                break;
            case Player.STATE_READY:
                // dismiss your dialog here because our video is ready to play now
                progressBar.setVisibility(View.GONE);
                break;
            case Player.STATE_ENDED:
                // do your processing after ending of video
                break;
        }
    }

    @Override
    public void onPlayerError(ExoPlaybackException error) {

        AlertDialog.Builder adb = new AlertDialog.Builder(VideoPlayerActivity.this);
        adb.setTitle("Could not able to stream video");
        adb.setMessage("It seems that something is going wrong.\nPlease try again.");
        adb.setPositiveButton("OK", new DialogInterface.OnClickListener() {
            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
                finish(); // take out user from this activity. you can skip this
            }
        });
        AlertDialog ad = adb.create();
        ad.show();
    }

    @Override
    public void onPositionDiscontinuity() {

    }

    @Override
    protected void onPause() {
        super.onPause();
        if (player != null) {
            player.setPlayWhenReady(false); //to pause a video because now our video player is not in focus
        }
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        player.release();
    }
}

我认为这对初学者来说已经足够了。另外请记住，该库的标准音频和视频组件依赖于 Android 的 MediaCodec API，该 API 在 Android 4.1（API 级别 16）中发布。所以它不适用于android 4.0及更低版本。

不要忘记将此权限添加到manifest file：

<uses-permission android:name="android.permission.INTERNET"/>

Answer 2

@Vicky 的答案会起作用，但有一个缺陷。

您传递给轨道选择器的带宽计必须与数据源工厂使用的相同。数据源工厂通过调用 BW Meter 方法来维护带宽估计，自适应轨道选择过程得到估计来决定适应哪个轨道。

如果它们不是同一个实例，则自适应选择总是将 -1 作为 BW，并选择一些中间选项。

演示 ExoPlayer 应用程序也有这个缺陷。他们将 false 传递给 buildDataSource() 中的 useBwMeter，这意味着不更新 BW 估计值编辑：实际上，此 BW 计量器用于清单加载程序。它不需要使用 BW 表。