android13/external/exoplayer/tree_15dc86382f17a24a3e881e52e31a810c1ea44b49/docs/retrieving-metadata.md

title
Retrieving metadata

During playback

The metadata of the media can be retrieved during playback in multiple ways. The most straightforward is to listen for the Player.Listener#onMediaMetadataChanged event; this will provide a [MediaMetadata][] object for use, which has fields such as title and albumArtist. Alternatively, calling Player#getMediaMetadata returns the same object.

public void onMediaMetadataChanged(MediaMetadata mediaMetadata) {
  if (mediaMetadata.title != null) {
    handleTitle(mediaMetadata.title);
  }
}

{: .language-java}

If an application needs access to specific [Metadata.Entry][] objects, then it should add a MetadataOutput (for dynamic metadata delivered during playback) to the player. Alternatively, if there is a need to look at static metadata, this can be accessed through the TrackSelections#getFormat. Both of these options are used to populate the Player#getMediaMetadata.

Without playback

If playback is not needed, it is more efficient to use the [MetadataRetriever][] to extract the metadata because it avoids having to create and prepare a player.

ListenableFuture<TrackGroupArray> trackGroupsFuture =
   MetadataRetriever.retrieveMetadata(context, mediaItem);
Futures.addCallback(
   trackGroupsFuture,
   new FutureCallback<TrackGroupArray>() {
     @Override
     public void onSuccess(TrackGroupArray trackGroups) {
       handleMetadata(trackGroups);
     }

     @Override
     public void onFailure(Throwable t) {
       handleFailure(t);
     }
   },
   executor);

{: .language-java}

Motion photos

It is also possible to extract the metadata of a motion photo, containing the image and video offset and length for example. The supported formats are:

• JPEG motion photos recorded by Google Pixel and Samsung camera apps. This format is playable by ExoPlayer and the associated metadata can therefore be retrieved with a player or using the MetadataRetriever.
• HEIC motion photos recorded by Google Pixel and Samsung camera apps. This format is currently not playable by ExoPlayer and the associated metadata should therefore be retrieved using the MetadataRetriever.

For motion photos, the TrackGroupArray obtained with the MetadataRetriever contains a TrackGroup with a single Format enclosing a [MotionPhotoMetadata][] metadata entry.

for (int i = 0; i < trackGroups.length; i++) {
 TrackGroup trackGroup = trackGroups.get(i);
 Metadata metadata = trackGroup.getFormat(0).metadata;
 if (metadata != null && metadata.length() == 1) {
   Metadata.Entry metadataEntry = metadata.get(0);
   if (metadataEntry instanceof MotionPhotoMetadata) {
     MotionPhotoMetadata motionPhotoMetadata = (MotionPhotoMetadata) metadataEntry;
     handleMotionPhotoMetadata(motionPhotoMetadata);
   }
 }
}

{: .language-java}

[MediaMetadata]: {{ site.exo_sdk }}/MediaMetadata.html [Metadata.Entry]: {{ site.exo_sdk}}/metadata/Metadata.Entry.html [MetadataRetriever]: {{ site.exo_sdk }}/MetadataRetriever.html [MotionPhotoMetadata]: {{ site.exo_sdk }}/metadata/mp4/MotionPhotoMetadata.html