play method
Implementation
Future play(List<FFMpegStream> streams) async {
final _streams = <int, FFMpegStream>{};
final vstream =
streams.indexWhere((s) => s.codecType == ffi.AVMediaType.VIDEO);
if (vstream >= 0) _streams[ffi.AVMediaType.VIDEO] = streams[vstream];
final astream =
streams.indexWhere((s) => s.codecType == ffi.AVMediaType.AUDIO);
if (astream >= 0) _streams[ffi.AVMediaType.AUDIO] = streams[astream];
await pause();
_pts = _PTS(_streams);
_pts!.playing = true;
return seekTo(0);
}