FFMPEG doesn't transcode the complete movie

[pluto1209]

I've used the FFMPEG from within GB PVR to transcode movies, and I tried in a command prompt with the same result. Whenever I try to transcode a movie or anything recorded longer than approx. 1h20min, FFMPEG stops transcoding after that time, it just does a normal exit without errors. This is the option that I have, do I miss one to transcode larger files ?

-f avi -vcodec xvid -b 1700 -ab 192

[sub]

What speed CPU have you got in your machine?

[pluto1209]

I've got a P4 2.6GHz and 1 GB ram

[sub]

Scratch that thought. I had a vague recollection that I had some logic that would kill the transcode process after a certain amount of time (thinking it'd never finish), but thats not the case - I removed that logic a long time ago.

To be honest, I dont know. Probably a bug in ffmpeg. I didnt see that here in my tests, but i cant remember for sure whether I recorded anything longer than that.

[pluto1209]

Thanks Sub...Is there someone else in the Forum that could say if they have used FFmpeg to transcode something longer than 1h20min ?

[GSpanFan]

I've recently ran into this problem. Large recordings stop transcoding at 01:27:54 using the xvid codec. Although the file sizes in bytes were proportionally what I'd expect for a fully transcoded file. Any suggestions? Maybe I've got an old xvid codec installed... (?)

[djtaylor]

If you search back, I found that mine were stopping at 1:46.33

I believe this is a problem with the libavcodec library that is used by both mencoder and ffmpeg and it's my belief that this struggles to deal with generated avi files that result in >1GB. Note, i'm not talking about the input size of the file, this is nothing to do with the original mpeg size.

Yes the resultant size is correct and can even be viewed via some software but I suspect that the library sets wrong values in the avi header.

If I reduced the encoding bitrate down to 900, I found that it worked just fine. Of course, for shorter movies, there's a lower bitrate hit that is unnecessary but it's an either or it seems without manual intervention.

Reduce the bitrate and my bet is that it will work fine.

David.

[GSpanFan]

Thanks for the suggestion David, I will try reducing the bitrate... although I'm reluctant to go to low and sacrifice on video quality especially for a 3 hour recording.

Also for anyone interested I was using an old Xvid codec and then upgraded to the newest version only to find out that the previously encoded videos wouldn't play (some kind of "pin" error). Thus I suspect I have an old/hacked/faulty codec in the first place that might be generating this error (or there's something wrong with the new one). I won't have access to my box I have GBPVR on for the next week or so, but will eventually post in this thread if I can find a workaround that doesn't involve reducing the bitrate.

[djtaylor]

Split the file in half or into 3 chunks then transcode?

[sgilani]

djtaylor has the right idea, I had an issue just like he's describing.. in MEncoder, using libavcodec gave the same error.

The way I got it to fix is by using XviD as the codec in mencoder (so you do -ovc xvid). It's a slower transcode, but I've seen it's much less blocky and gives better quality. It happens overnight anyway after all, so I don't care if it takes a little longer.

fwiw, this works wonders for me: (the bitrate I use is pretty high; if you're just going to watch the recording you should drop the bitrate and resolution.. 512x384 @ 1000 bitrate should be very nice)

mencoder <input_file> -ovc xvid -xvidencopts bitrate=2000:me_quality=6:noqpel:chroma_me:bvhq=1:trellis:hq_ac:quant_type=mpeg -oac mp3lame -lameopts mode=2:cbr:br=128 -vf softskip,scale=640:480 -forceidx -ofps 29.97 -o <output_file>

If you want to use GBPVR's built-in processing function, just stick mencoder in the Third Party\ffmpeg folder and rename it to ffmpeg.exe, and update the config.xml to an mencoder-type command line.