On Fri, Sep 17, 2010 at 10:36 AM, Tomas Härdin <[email protected]>wrote:
> On Thu, 2010-09-16 at 20:11 +0400, Kulti wrote: > > On Thu, Sep 16, 2010 at 5:34 PM, Tomas Härdin <[email protected] > >wrote: > > > > > Please don't top post on this list. It makes it harder for people to > > > read it. > > > > > > On Thu, 2010-09-16 at 17:02 +0400, Kulti wrote: > > > > Hm... Thanks, I'm use flv-container, but how to set VFR? It's mean, > that > > > I > > > > need to modify AVCodecContext.time_base before encoding every frames? > > > > > > > > On Thu, Sep 16, 2010 at 4:43 PM, Tomas Härdin < > [email protected] > > > >wrote: > > > > > > > > > On Thu, 2010-09-16 at 13:36 +0400, Kulti wrote: > > > > > > Hi, all. > > > > > > > > > > > > I have a webcam and need to transcode mjpeg to any formats, but > > > sometime > > > > > > webcam lagged and fps fall down. Can ffmpeg atuo fill dropped > frames > > > to > > > > > > constantly fps? > > > > > > > > > > Why do you want constant fps? Just use a container that handles VFR > > > > > (avi, flv, mov etc.). > > > > > > > > > > Anyway, assuming the frames are timestamped correctly ffmpeg should > > > > > behave correctly. If not, try forcing constant framerate with -r. > > > > > > > > > > /Tomas > > > > > > > > > > > FLV has a fixed time base of 1 kHz, so it's always VFR. In other cases, > > > like AVI, you can set time_base to be less than or equal to the inverse > > > of the maximum fps. > > > > > > In other words, if you know your camera can't deliver more than 50 fps > > > you can set time_base to 1/50, 1/123, 1/10000 or whatever. In the > > > specific case of AVI you shouldn't set it too low though, since it pads > > > with empty packets for the "missing" time stamps (IIRC something like > > > 39*16 = 624 B overhead if you mux 25 fps with a time base of 1 kHz). > FLV > > > does not have this problem though. > > > > > > Hope that helps :) > > > > > > /Tomas > > > > > > _______________________________________________ > > > libav-user mailing list > > > [email protected] > > > https://lists.mplayerhq.hu/mailman/listinfo/libav-user > > > > > > > > Sorry for top-post... and thanks for your help. > > > > So, I set time_base to fixed value 1/25 (that I get from AVCodecContext > for > > mjpeg-decoder). Then I added timer and frame-counter before > > av_write_frame(). I see, that fps is 19-21. But I need live-streaming. > So, I > > hardcoded time_base to 1/20, and all works fine before webcam is not lag, > > but after fall down fps to 15 transcoding process broken. > > > > Yes, I understand, that must be working for transcoding into file, but I > > need real-time transoding for live streaming. I can't see any way instead > > inserting frames, when some drops... > > What you do is convert the current time to the stream's time base, and > stick that value in as the packet's DTS. Sort of like this: > > //remember what the time was when the program started > int64_t t0 = get_microseconds_time(); //replace with whatever function > is suitable > > ... > //for each AVPacket > int64_t t = get_microseconds_time(); > pkt->dts = av_rescale_q(t - t0, AV_TIME_BASE_Q, st->time_base); > av_write_frame(...); > > That seconds line converts your zero-centered times from microseconds to > the stream's time base. This means if the camera suddenly slows down a > bit, the DTS value will have gaps. This is fine as long as the muxer can > handle VFR (such as AVI and FLV). > > /Tomas > > _______________________________________________ > libav-user mailing list > [email protected] > https://lists.mplayerhq.hu/mailman/listinfo/libav-user > > Thanks! I'm not familiar with pts, dts etc. May be you can advise me any docs? In my application I already have rescale for pts: avPacket->pts = av_rescale_q(codedFrame->pts, pCodecCtx->time_base, pVideoStream->time_base); and I've added rescale for dts too: avPacket->dts = av_rescale_q(getTimeMicroSeconds() - startEncodingTimeMicroSeconds, AV_TIME_BASE_Q, pVideoStream->time_base); but after any seconds I've received error message: st:0 error, pts < dts So, I added following code: if( avPacket->pts < avPacket->dts ) avPacket->pts = avPacket->dts; Is it right way? Now it works about 50 minutes and other error displayed: st:0 error, non monotone timestamps 2885736 >= -1385734 As I understand from ffmpeg sources, it's meaning, that stream's dts >= packet's dts, but I have not any idea to fix them. _______________________________________________ libav-user mailing list [email protected] https://lists.mplayerhq.hu/mailman/listinfo/libav-user
