On 07/27/2012 08:34 PM, James Walker wrote: > Hello, > > I'm a C.S. graduate student working on developing an optical > tracking system as part of my research. I'm trying to > figure out the best way to get a working, low-latency > feed from an Ethernet camera. Unfortunately, when > connecting to the camera with UDP, the image is badly > corrupted. It gives errors such as the following: > > Input #0, rtsp, from 'rtsp:// > username:[email protected]/axis-media/media.amp': > Metadata: > title : Media Presentation > Duration: N/A, start: 0.099878, bitrate: N/A > Stream #0.0: Video: h264 (Baseline), yuvj420p, 640x480 [PAR 1:1 DAR > 4:3], 90k tbr, 90k tbn, 180k tbc > [avsink @ 0x7f9624001020] auto-inserting filter 'auto-inserted scaler 0' > between the filter 'src' and the filter 'out' > [scale @ 0x7f9624001700] w:640 h:480 fmt:yuvj420p -> w:640 h:480 > fmt:yuv420p flags:0x4 > [h264 @ 0x7f962c0073a0] corrupted macroblock 15 27 (total_coeff=-1)/0 > [h264 @ 0x7f962c0073a0] error while decoding MB 15 27 > [h264 @ 0x7f962c0073a0] concealing 154 DC, 154 AC, 154 MV errors > [h264 @ 0x7f962c0b7760] negative number of zero coeffs at 29 12 > [h264 @ 0x7f962c0b7760] error while decoding MB 29 12 > [h264 @ 0x7f962c0b7760] concealing 740 DC, 740 AC, 740 MV errors > 5.05 A-V: 0.000 s:0.0 aq= 0KB vq= 0KB sq= 0B f=0/0 > > Lots of Google searching has revealed that this is a fairly > widespread problem common to both ffmpeg and avlib. We've > tried multiple versions of both libraries, but the problem persists. > It appears to be some kind of bug in the UDP protocol. > If I specify the connection to use TCP instead; e.g., > > avplay 'rtsp://username:[email protected]/axis-media/media.amp?tcp' > > then it works, but the latency is very high (~1 sec) which > is not good enough for an optical tracking system. > > Either fixing UDP or significantly improving the latency > of the TCP connection would be an acceptable solution > to the issue. Our research group probably has the > knowledge needed to modify the code ourselves, but > this would be significantly easier if we had some > guidance beforehand, rather than just diving right in. > Would anyone be able to advise me in this issue? > > Thank you for your time. >
add -threads 1 to avplay and -analyzeduration 0 and either force the udp buffer to be incredibly large or use tcp. I hope it helps =) lu -- Luca Barbato Gentoo/linux http://dev.gentoo.org/~lu_zero _______________________________________________ libav-api mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-api
