.ogg is stuttering when play

[rbattaglin25]

We noticed when the file .ogg contains the instrument "Reco Reco" the audio is stuttering in some specific devices. For example, Samsung Galaxy Tab S3 with SDK 28.

https://github.com/rbattaglin25/poc_exoplayer.git

Here is a small project using exoplayer that has this problem.

[christosts]

I am not an audio compression/codec expert but this sounds unrelated to ExoPlayer and more related to the device's audio decoder. I tried playing a few the ogg files in the repo that you linked but I did not observe any audio stuttering.

Some ideas:

• If you play the specific ogg files on the same devices with another player, do you still observe the issue?
• Are you using the audio codecs that come with the device/platform? Can you try the ffmpeg extension to decode audio with ffmpeg?

[rbattaglin25]

If you play the specific ogg files on the same devices with another player, do you still observe the issue?

Yes, I'm using the MediaPlayer is this PoC and it's working.

Are you using the audio codecs that come with the device/platform? Can you try the ffmpeg extension to decode audio with ffmpeg?

I'm trying to generate this file but I can't because I have to export in eight channels. Do you have any idea how to do it?

I did more tests and noticed that Xiaomi Mi9, Galaxy A50 and Moto G9 power has this problem.

In this PoC has more .ogg files without the instrument "Reco Reco" and if you play works fine .You can test this.

[christosts]

I'm trying to generate this file but I can't because I have to export in eight channels. Do you have any idea how to do it?
I'm afraid I cannot assist with this.

At this point, I assume there's something wrong with the platform's decoder on this specific devices, and I'd advise to try ExoPlayer with the ffmpeg extension so that the player uses ffmpeg for decoding the audio files.

@krocard any other thoughts/recommendations on this issue?

[krocard]

Playing your POC and our demo app with the android emulator (pixel 3XL), I could hear audio underruns.
I believe the issue comes from very high bitrate of your audio file:

$ mediainfo app/src/main/res/raw/choro_with_recoreco.ogg
Format                                   : Ogg
File size                                : 3.04 MiB
Duration                                 : 10 s 435 ms
Overall bit rate mode                    : Variable
Overall bit rate                         : 2 440 kb/s

Audio
Format                                   : Vorbis
Bit rate mode                            : Variable
Bit rate                                 : 1 919 kb/s
Channel(s)                               : 8 channels

On low end devices like the emulator, the decoder has a very hard time decoding fast enough for real time playback. It barely manages it, but with a lot of variability. Some frames take sometime a very long time to decode, which starves the audioTrack, leading to an audible underrun.

The reason that MediaPlayer is not (as) affected compared to AudioTrack is that it uses an audio buffer twice as big. This can easily be observed by doubling MIN_BUFFER_DURATION_US to .5s:

ExoPlayer/library/core/src/main/java/com/google/android/exoplayer2/audio/DefaultAudioSink.java

Lines 256 to 257 in bd54394

	/** A minimum length for the {@link AudioTrack} buffer, in microseconds. */
	private static final long MIN_BUFFER_DURATION_US = 250_000;

[krocard]

I would recommend lowering the bitrate of the audio file played. 8 channel 1.9kb/s is an extremely low compression ratio (only ~35%). I guess the highest quality setting of libvorbis was used to encode them. Halving the bitrate should provide ample enough quality for playback.