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