ExoPlayer TextRenderer 轨道丢失

Question

对于 ExoPlayer 2.18.2，我正在初始化一个 DefaultTrackSelector

trackSelector = DefaultTrackSelector(requireContext())

并将其附加到播放器

private fun createContentPlayer() {
    val renderersFactory = DefaultRenderersFactory(requireContext())
    this.trackSelector = DefaultTrackSelector(requireContext())

    val player = ExoPlayer.Builder(requireContext())
        .setRenderersFactory(renderersFactory)
        .setTrackSelector(this.trackSelector!!)
        .build()

    this.contentPlayer = player
}

所以我有这个方法来检索文本渲染器索引

private fun getTextRenderIndex(): Int {
    val count = contentPlayer?.rendererCount ?: 0
    for (i: Int in 0..count) {
        if (contentPlayer?.getRendererType(i) == C.TRACK_TYPE_TEXT) {
            return i
        }
    }

    return -1
}

文本渲染器索引始终为 2（请参见下面屏幕截图中的索引）

媒体源是这样准备的

val uri = Uri.parse("video.m3u8")

val dataSourceFactory = DefaultDataSource.Factory(requireContext())

val mediaSource = HlsMediaSource.Factory(dataSourceFactory).createMediaSource(MediaItem.fromUri(uri))

contentPlayer?.setMediaSource(mediaSource)
contentPlayer?.prepare()

好的，到目前为止没问题，但是如果我打电话

val mappedTrackInfo = trackSelector?.currentMappedTrackInfo

然后在调试器中查看 MappedTrackInfo 对象，渲染器名称是

["MediaCodecVideo...", "MediaCodecAudio...", "TextRenderer", "MetadataRendere...", "CameraMotionRen..."]

但是同一对象中的 rendererTrackGroups 显示没有文本轨道

为什么缺少文本渲染器？

应用程序正在播放的视频是 .m3u8，并且通常嵌入了隐藏式字幕。但到目前为止，我还没有看到任何隐藏式字幕渲染。所以我猜原因是文本渲染轨道不存在。

我的目标是能够使用以下代码打开/关闭视频的隐藏式字幕

val length = trackGroupArray?.length ?: 0
if (length > 0) {
    val trackGroup = trackGroupArray!![0]

    val currentParamsBuilder = trackSelector?.buildUponParameters()
            ?: DefaultTrackSelector.Parameters.Builder(requireContext())

    val disabled = !enabled

    if (trackGroup.length > 0) {
        val selectionOverride = TrackSelectionOverride(trackGroup, 0)
        val newParameters = currentParamsBuilder
            .setRendererDisabled(textRenderIndex, disabled)
            .clearOverridesOfType(TRACK_TYPE_TEXT)
            .addOverride(selectionOverride)
            .build()

        trackSelector?.parameters = newParameters
    }
}