Need help with ffmpeg transcoding

[Anthony]

I record SD and HD television shows with GBPVR and the Hauppauge HVR-1600 and HVR-2250 tuner cards. While these turn out fine, there are some playback issues on my Tvix M6500 that I'm trying to solve by transcoding.

I have found if I transcode to an MP4 file with MP4 video and AAC audio the playback works perfectly. However, shows with 5.1 audio end up kind of weird sounding when transcoded into 6 channel. It's like it gets downmixed to stereo on just the left and center channel or something. Hard to explain.

This is the commandline I am using:

"C:\program files\ffmpeg\ffmpeg.exe" -i D:\clip.mpg -threads 4 -vcodec mpeg4 -b 12000k -acodec libfaac -ab 192kb -ac 6 d:\test.mp4

Any ideas what I can do to retain the full 5.1 audio tracks?

I also need to retain compatibility for standard def channels with 2 channel stereo tracks.

I'm not concerned about file sizes.

Thanks,

Anthony

[mvallevand]

Rather than transcoding, have you tried TS4NP or TSResumux? The M6500 uses the same Sigma chip as the Popcorn Hour and it suffers many of the same playback problems. These programs fix several of them.

Martin

[Anthony]

Martin,

I just tried both of the programs you suggested, with identical results. It appears to fix some of the timeline issues (i.e. remaining time is calculated correctly), but there's no sound when played back on the 6500.

For what it's worth, I've also tried the "quick stream fix" in VideoRedo, as well as loading and resaving, but it doesn't change the playback issue.

Transcoding to MP4 seems to work the best if I can figure out the audio problem.

Anthony

[mvallevand]

Could you provide a small 80 MB sample of a "bad" source file via megaupload or other free site? I'd like to have a listen.

Martin

[Anthony]

Hi Martin,

I uploaded a sample clip to:

http://www.mountain-software.com/clip.mpg

The file plays fine except for two minor issues on the M6500.

1. The video plays fine for 8 minutes or so, pauses for 5 seconds, plays another 10-15 minutes, pauses 5-8 seconds, and so on. Obviously, you won't be able to duplicate this with a 45 second clip, but it occurs repeatedly at the same spot in the same file, but does NOT occur with all files. It's not related to the data rate as I can play other HD files over my network without issues.

2. The M6500 doesn't report the show length correctly. It just says "N/A" for the remaining time.

I can't see anything wrong with the file on my PC, but transcoding to MP4 seems to fix both problems if I can overcome the sound issue.

Anthony

[Anthony]

Martin,

I think I may have stumbled across a solution. If I load the MPG file into VideoRedo and save it out as a TS file, it plays perfectly on the M6500. No pauses, the time displays work perfectly, no reencoding necessary, and it seems like the fast forward and rewind operations actually work well (though I would need more testing for that).

Ironically, loading the TS file and saving back to a MPG file again makes the problem reappear. So the M6500 obviously has some problem with MPG files.

Now I just need to figure out how to make the conversion to TS, calling VideoRedo from the command line.

I currently use this line in my batch file to strip commercials from the source file that comskip locates:

cscript //nologo "C:\Program Files\VideoReDoPlus\vp.vbs" "%~dpn1.VPrj" "%~dpn1_clean.mpg" /t1 /q

Ideally, I'd like to save directly to TS and skip the second conversion step, but I don't know if that's possible, or if it would still solve the issues I'm having without going through the two steps.

Time to do more research...

Anthony

[Anthony]

Well, that was easy....

I just changed this line in my batch file:

cscript //nologo "C:\Program Files\VideoReDoPlus\vp.vbs" "%~dpn1.VPrj" "%~dpn1_clean.mpg" /t1 /q

To this:

cscript //nologo "C:\Program Files\VideoReDoPlus\vp.vbs" "%~dpn1.VPrj" "%~dpn1_clean.ts" /t4 /q

Now VideoRedo strips the commercials as before, but saves the show as a TS file instead of an MPG file. I'll need to do more testing, but so far it seems to work perfectly, with no additional transcoding steps needed!

Anthony

[mvallevand]

I'm glad you found a solution. I was going to ask for the source TS file since a muxed or transcoded mpeg file could not be trusted to give good results on a hardware player.

Martin