Audio sync with H.264/mpeg-4 and AAC

[Octathorpe]

I am finding that the audio gets out of sync with the video when I play back .mp4 files on the HD extender. I'm wondering if this is a problem with my setup or files or if anyone else has seen this issue.

I can play the files back locally on the server using either the SageTV client or other playbck apps and there is not sync problem.

The sync is fine at the start of the file and gets progressively more out of sync towards the end of the movie. At the 1.5 hour mark it's several seconds off. Not all files have the same delay. I'm using the latest firmware.

Example file specs from GSpot: video is avc1 H.264/mpeg-4 AVC with a framerate of 23.976 and audio is mp4a AAC low complexity at 48KHz stereo. It is an .mp4 wrapper made on a mac with handbrake. A file with identical properties made on a PC with Nero Digital had very litle delay (but still noticable at 0.5 s after 1.8 hours). Is this an encoder issue? Could be framerate related? Why does it play back fine using the local client?

An AVI file with H.264/mpeg-4 AVC and dolby AC3 audio at 48KHz behaved fine.

Thanks for any suggestions.

[Octathorpe]

Bump.

I have not been able to correct this issue yet. Can anyone let me know if you have seen a similar sync problem? Or let me know what other information I can provide.

Thanks.

[reggie14]

I've had pretty much the exact same problem with the same kind of video/audio file. I think fast forwarding or rewinding also causes synchronization problems.

[Octathorpe]

I am running some tests on long .mp4 files now to see if they stay in sync if I start playing and don't do any ff or rew. It will (obviously) take a few hours to gather the data. If it is indeed related to the ff/rew actions, then it really narrows down the problem.

[Octathorpe]

I tried two H.264 mp4 files and if I play them from the start without any ff or rewind then they stay in sync through the whole movie.

If I fast forward the file, then it will get out of sync, and more so the farther into the movie you go.

This was not a comprehensive test by any means, but it does seem to indicate that for some reason, H.264 files with a .mp4 wrapper are not handled correctly by the fast forward function.

[reggie14]

Octathorpe-

I updated my firmware today and, after limited testing, it appears the synchronization problems are fixed. Hopefully it works for you too.