[MPlayer-users] Jumpy AVIs when encoding from TV tuner

[Jindrich Makovicka]

Richard Dymond wrote:

>[Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
>Hi.
>
>I've looked in the mailing list archives and the documentation, but I
>can't find anything relevant to my problem. (There might be something
>there - in which case flame me! - but it didn't jump out at me.)
>
>So what is the problem? Encoding from my Hauppauge WinTV PVR. Picture
>and sound are mostly fine in the resultant AVI, but every few minutes
>or so, for about 20 seconds, the picture will become jumpy, as if
>sequences of several frames are being skipped. (A/V sync remains good,
>though.) If I use the -noskip option, this seems to fix the jumpy
>picture, but at the expense of A/V sync. With -noskip, the A/V sync will
>be fine up to a point, and suddenly become about half a second or so out.
>
>Here's the mencoder command I'm using:
>
>mencoder -tv on:driver=v4l:freq=719.187:outfmt=yv12:width=768:height=576 \
> -ovc lavc -lavcopts vcodec=mjpeg:vqscale=3 \
> -vop scale=384:288,crop=760:568:4:4 -oac copy -o tv.avi
>
>Before anyone asks: I capture at 768x576 and then scale to 384x288 because
>capturing at 384x288 gives a *very* poor picture. (384x288 seems to be
>a critical resolution: anything below that looks awful, above is fine.)
>I encode to MJPEG because that allows me to use the mjpegtools utilities 
>to edit the result before doing a final encoding to MPEG4/MP3. At least,
>it *should*, but the mjpegtools utilities don't work on any AVI that has
>"jumps" in it. If I'm lucky enough to produce an AVI with mencoder that
>*isn't* jumpy, mjpegtools is happy; but any AVI more than a few minutes
>long invariably has jumps in it.
>
>So, could I be "mencoding" more sensibly? Am I missing some crucial
>options? Is this - gasp! - a bug?
>  
>
Even worse, it's a feature. MEncoder can occasionally drop a video frame 
(or more precisely insert an empty frame) to maintain the a/v sync. But 
usually it shouldn't be more than about 20 frames/hour.

Regards,

-- 
Jindrich Makovicka