Audio sync more information

Audio sync seems to have some issues still, I gathered a little more information today that I’d like to share in case it helps anyone figure something out. The particular device here is a gen2 wdtv but it seems exactly the same on the “live” one though I haven’t tested extensively as I dont have easy access to one, have to visit a friend.

Last night I watched 2 hours of MP4 video downloaded from my TiVO through their standard desktop software and converted to an MP4 file with AAC audio via Handbrake without issue. Fast forwarded through commercials and while it did drop a few frames (it was an HD 1080p file) the quality and sync were perfect. No problems at all. MP4 file H.264 video and AAC encoded stereo audio.

Today I tried to load up some short TV shows encoded and loaded exactly the same way for the kids and the audio is horribly out of sync. The only difference between the 2 and how they were encoded was that I had edited these to remove the commercials from the kids favorite shows. With each edit or fast forward/rewind action it seemed to get worse, but the editing definitely did something. In my case I edited it with QuikTime pro and re-exported without re encoding the audio/video so it just clipped the mp4 streams inside the files. This plays back perfect on various computers and iPods but not so on the WDTV.

If I go back to the original, unedited mp4 file it plays perfectly, but I have to fast forward them through the commercials.

If I re-encode the edited file just remuxing but not actually re-encoding the data it’s exactly the same out of sync.

If I re-encode the file and actually re-encode the audio and video then it’s in perfect sync UNTIL it hits the first commercial edit then it’s off again. Or if I watch a file that I didn’t trim anything off the beginning it’s in sync until it hits the first other edit it’s fine until then too.

I tried re-encoding as am MKV file with MP3 audio as was recommended here and elsewhere but that did nothing for the sync at all, still broken.

I have these example files and can probably generate more, should I send them somewhere? Does that offer any hints? Thank you!

Where you looking to provide WD with information?  Or were you looking for something else?