Cache for hls video using exoplayer in android - caching

Question

Is it possible to create a cache for hls type videos when playing in exoplayer , so that once video completely streamed then no need to load again, and start playing immediately for the next time when play button clicked, If possible please provide any solution? The video format is .m3u8 type.

Answer 1

For non ABR streams, i.e. not HLS or DASH etc
There is a well used library which provides video caching functionality:
https://github.com/danikula/AndroidVideoCache
Bear in mind that large videos will use a lot of memory so you may want to consider when and where you want to cache.
Update for ABR streams
Adaptive Bit Rate Streaming protocols like HLS or DASH typically have segmented multiple bit rate versions of the video, and the player will download the video segment by segment, choosing the bitrate for the next segment depending on the network conditions and the device capabilities.
For this reason, simply storing what you are viewing may not give you the result you want - for example if you have some network congestion part way through the video you may receive lower quality segments, which you probably don't want for a video you will watch multiple times.
You can download or play a video, forcing the stream to always select from one specific resolution by using a track selector. ExoPlayer documentation includes some info here:
https://exoplayer.dev/downloading-media.html
In an older blog post (2 years old but the DownloadHelper part is still relevant, I think), Google provide info on how to use the DownloadHelper - https://medium.com/google-exoplayer/downloading-adaptive-streams-37191f9776e.
This includes the example:
// Replace with HlsDownloaderHelper or SsDownloadHelper if the stream is HLS or SmoothStreaming
DownloadHelper downloadHelper =
new DashDownloadHelper(manifestUri, manifestDataSourceFactory);
downloadHelper.prepare(
new Callback() {
#Override
public void onPrepared(DownloadHelper helper) {
// Preparation completes. Now other DownloadHelper methods can be called.
List<TrackKey> trackKeys = new ArrayList<>();
for (int i = 0; i < downloadHelper.getPeriodCount(); i++) {
TrackGroupArray trackGroups = downloadHelper.getTrackGroups(i);
for (int j = 0; j < trackGroups.length; j++) {
TrackGroup trackGroup = trackGroups.get(j);
for (int k = 0; k < trackGroup.length; k++) {
Format track = trackGroup.getFormat(k);
if (shouldDownload(track)) {
trackKeys.add(new TrackKey(i, j, k));
}
}
}
}
DownloadAction downloadAction = downloadHelper.getDownloadAction(null, trackKeys);
DownloadService
.startWithAction(context, MyDownloadService.class, downloadAction, true);
}
private boolean shouldDownload(Format track) {...}
#Override
public void onPrepareError(DownloadHelper helper, IOException e) {...}
});
The code above look at the manifest file - this is the index file for DASH or HLS which lists the individual tracks and provides info, e.g. URLs, of there to find them.
It loops through each track that it finds and calls a function which you can define as you want to decide whether to include or exclude this track from the download.
To use track selection when playing back a streamed video, you can control this programatically using the DefaultTrackSelector: https://exoplayer.dev/track-selection.html. This link includes an example to select SD video and German Audio track:
trackSelector.setParameters(
trackSelector
.buildUponParameters()
.setMaxVideoSizeSd()
.setPreferredAudioLanguage("deu"));
The standard player also allows a user select the track from the controls if you are displaying controls - the ExoPlayer demo app () includes this functionality and the user view should look something like:
One note - ABR streaming is quite complex and requires extra processing and storage on the server side. If you expect to only use one quality level then it may make more sense to simply stream or download the videos as mp4 etc.