NuPlayerRenderer latency calculation bug?

[Sangyoun Lee]

Hi all,

I am working with external speaker which has large buffer. The audio latency is over 3 secs.

By the way, AV was out of sync in NuPlayer and there is a suspicious code in NuPlayerRenderer.cpp.(With AwesomePlayer, AV is in sync.)

Test env. - aosp 5.0.2_r1, Nexus7(flo)

https://android.googlesource.com/platform/frameworks/av/+/master/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp

line 1341-1347

1.     } else {                         // case 3: transitory at new track or audio fast tracks.
2.         res = mAudioSink->getPosition(&numFramesPlayed);
3.         CHECK_EQ(res, (status_t)OK);
4.         numFramesPlayedAt = nowUs;
5.         numFramesPlayedAt += 1000LL * mAudioSink->latency() / 2; /* XXX */
6.         //ALOGD("getPosition: %d %lld", numFramesPlayed, numFramesPlayedAt);
7.     }

I do not understand why this division is needed:"mAudioSink->latency() / 2".

I have tested after removing the division: "numFramesPlayedAt += 1000LL * mAudioSink->latency();"

AV is in sync now. 

This looks like a bug. Is there anyone who has any ideas about this code?

Thanks,

Sangyoun

[Sangyoun Lee]

I found that mAudioSink->latency(_) does not work properly.

frameworks/av/media/libmedia/AudioTrack.cpp

1244     // FIXME don't believe this lie
1245     mLatency = afLatency + (1000*frameCount) / mSampleRate;

I had better find another way to resolve this issue.

Thanks,

Sangyoun

[Glenn Kasten]

Yes, this is a difficult situation :-(

The problem is that afLatency does not take into account all the components of the latency,

and is not always up-to-date for the current path to the sink.

[Sangyoun Lee]

Thank you, I have one more question.

I did not implement 'audio_hw.c' for our device yet. It means that get_presentation_position( ) function is not implemented, so in NuPlayerRender, getTimestamp( ) fails and then the XXX code runs.

Could you give me the best way to fix this? Implementing 'audio_hw.c' for our device is the best way?

Thanks again,

Sangyoun

[Glenn Kasten]

Yes, you need to implement this API for the A/V sync to work.