Problem with AC3 stream when converting to WMV

[RCSea]

I recently got a CableCard and switched to digital cable (Comcast, Seattle). Before that, for about a year now I had been successfully using DirectShowDump and WinFF (windows gui for FFMpeg) to convert .Tivo files to wmv format for playback on my Gigabeat.

Since the switch, I now have a very annoying audio problem with the converted files, and I can't figure out where exactly things are going wrong. The audio in the wmv file is out of sync, and it varies with each recording. And on top of that, there a weird pulsing humming echo introduced.

DirectShowDump converts the .Tivo file to .mpg without complaining. I don't have an mpeg2 video decoder but if I play the .mpg file in WMP the audio sounds normal (although I can't tell if it's out of sync). When I then run it through FFMpeg, the wmv file does get created but I get this in the log:

Input #0, mpeg, from 'D:\Tivo Videos\Test.mpg':
Duration: 00:30:02.01, start: 1.000000, bitrate: 3798 kb/s
Stream #0.0[0x1bd]: Audio: ac3, 48000 Hz, stereo, s16, 192 kb/s
Stream #0.1[0x1e0]: Video: mpeg2video, yuv420p, 528x480 [PAR 40:33 DAR 4:3],
15000 kb/s, 29.97 tb(r)
Output #0, asf, to 'D:\Tivo Videos\Test.wmv':
Stream #0.0: Video: wmv2, yuv420p, 320x240 [PAR 1:1 DAR 4:3], q=2-31, 500 kb
/s, 29.97 tb(c)
Stream #0.1: Audio: wmav2, 44100 Hz, stereo, s16, 128 kb/s
Stream mapping:
Stream #0.1 -> #0.0
Stream #0.0 -> #0.1
Press [q] to stop encoding
[ac3 @ 0x19745a0]frame sync error
Error while decoding stream #0.0
[ac3 @ 0x19745a0]incomplete frame
[ac3 @ 0x19745a0]invalid frame size
[ac3 @ 0x19745a0]incomplete frame
[ac3 @ 0x19745a0]invalid frame size
[ac3 @ 0x19745a0]incomplete frame
[ac3 @ 0x19745a0]invalid frame size
...
with hundreds of the incomplete frame/invalid frame size errors repeating.

I've tried installing the AC3Filter codec but it makes no difference (ffmpeg probably doesn't even know its there).

So, anyone have an idea if this is a problem with the original AC3 stream being broadcast, a problem with how my HDTivo is recording it, with the transfer using Tivo Desktop (2.7 or 2.6.2, same problem), with DirectShowDump, or with FFMpeg? And what I might do about it?

[Dan203]

Not trying to be a company shill, but you should try VideoReDo.

If you want to keep your current work flow then you can just use it's Quick Stream Fix feature as a replacement for DirectShow Dump. (VRD can open TiVo files directly and output them to unencrypted mpg files) Or if you want to get fancy you can actually open the file in the editor and get rid of the commercials first. In either case VRD will correct any problems in the stream during output, which should eliminate the problem causing the WinFF error.

There is a 15 day trial so it wont cost you anything to try it out and see if it fixes the problem.

Dan

P.S. We will be releasing a new version in the next couple months that will allow you to transcode directly to WMV inside VRD. So you'll be able to convert your TiVo files to WMV in a single step. :)