Hi Alex, Seems I couldn't find the source code of av_frame_get_best_effort_timestamp, so I have to ask here, because I found that ffmpeg 1.1.3 return -1 for every frame of same file.
So definitely int64_t position = av_frame_get_best_effort_timestamp(pFrame); if ((position != AV_NOPTS_VALUE) && (position >=0)) is needed to check if best effort timestamp is valid, but I'd like to know if it's enough. As you can see in ffmpeg2.0.1 (with which av_frame_get_best_effort_timestamp returns correct value) the best effort time stamp returned equals to frame.pkt_dts, that's ok. But if it's possible, for exmpale, av_frame_get_best_effort_timestamp returns all 0 for every frame? So in summary I'd like to know on what condition can I totally trust time stamp returned by this function (so I can forget about those packet.dts, packet.pts, frame.pkt_dts) Thanks! 2013/10/30 YIRAN LI <[email protected]> > Thanks Alex, > > I just had a quick check, called > av_frame_get_best_effort_timestamp(pFrame); and seems > pFrame->best_effort_timestamp was filled with desired values (1st frame > having 0, 2nd having 1 and so on). > > I'll read through the link you gave me later on. > > Great Thanks! > > > 2013/10/30 Alex Cohn <[email protected]> > >> On Wed, Oct 30, 2013 at 5:51 AM, YIRAN LI <[email protected]> wrote: >> > >> > Hi friends, >> > >> > Here I have a question about AVFrame pts needs your help. >> > >> > My application uses av_read_frame to get packets and then calls >> avcodec_decode_video2 to get video frames. But recently I found one >> specific video file generates strange pts/dts. >> > >> > Below is a part of the log: >> > >> > 00:00:17.301 MAIN timestamp_debug: pkt.pts = -9223372036854775808, >> dts = 0 >> > 00:00:17.301 MAIN timestamp_debug: frame.pkt_pts = >> -9223372036854775808, frame.pkt_dts = -9223372036854775808, frame.pts = >> -9223372036854775808 >> > 00:00:17.301 1108 FFMPEG: looks like this file was encoded with >> (divx4/(old)xvid/opendivx) -> forcing low_delay flag >> > >> > 00:00:17.301 MAIN timestamp_debug: pkt.pts = -9223372036854775808, >> dts = 1 >> > 00:00:17.301 MAIN timestamp_debug: frame.pkt_pts = >> -9223372036854775808, frame.pkt_dts = -9223372036854775808, frame.pts = >> -9223372036854775808 >> > 00:00:17.301 MAIN timestamp_debug: pkt.pts = -9223372036854775808, >> dts = 2 >> > 00:00:17.301 MAIN timestamp_debug: frame.pkt_pts = >> -9223372036854775808, frame.pkt_dts = -9223372036854775808, frame.pts = >> -9223372036854775808 >> > 00:00:17.301 MAIN timestamp_debug: pkt.pts = -9223372036854775808, >> dts = 3 >> > 00:00:17.301 MAIN timestamp_debug: frame.pkt_pts = >> -9223372036854775808, frame.pkt_dts = -9223372036854775808, frame.pts = >> -9223372036854775808 >> > 00:00:17.301 MAIN timestamp_debug: pkt.pts = -9223372036854775808, >> dts = 4 >> > 00:00:17.301 MAIN timestamp_debug: [a full frame : frame.pkt_pts = >> -9223372036854775808, frame.pkt_dts = 0], frame.pts = 0 >> > 00:00:18.393 LVid236 timestamp_debug: pkt.pts = >> -9223372036854775808, dts = 5 >> > 00:00:18.408 LVid236 timestamp_debug: [a full frame : frame.pkt_pts >> = -9223372036854775808, frame.pkt_dts = 1], frame.pts = 0 >> > 00:00:18.439 LVid236 timestamp_debug: pkt.pts = >> -9223372036854775808, dts = 6 >> > 00:00:18.439 LVid236 timestamp_debug: [a full frame : frame.pkt_pts >> = -9223372036854775808, frame.pkt_dts = 2], frame.pts = 0 >> > 00:00:18.439 LSou259 FFMPEG: first_dts 0 not matching first dts >> 113424 in the queue >> > 00:00:18.486 LVid236 timestamp_debug: pkt.pts = >> -9223372036854775808, dts = 7 >> > 00:00:18.486 LVid236 timestamp_debug: [a full frame : frame.pkt_pts >> = -9223372036854775808, frame.pkt_dts = 3], frame.pts = 0 >> > 00:00:18.517 LVid236 timestamp_debug: pkt.pts = >> -9223372036854775808, dts = 8 >> > 00:00:18.517 LVid236 timestamp_debug: [a full frame : frame.pkt_pts >> = -9223372036854775808, frame.pkt_dts = 4], frame.pts = 0 >> > 00:00:18.549 LSou259 FFMPEG: first_dts 0 not matching first dts >> 114675 in the queue >> > >> > We can see that, it was until 4th packet is sent to decode function >> that we got the first full frame. and all frames had pts = 0 >> > >> > So here I want to know, frame.pts, frame.pkt_dts, packet,dts. which is >> best to represent the time stamp of a video frame (I mean pts, but in this >> case, no pts is valid). >> > >> > For example, in this case, for the 1st frame, should I use >> frame.pkt_dts (that's 0), or pkt.pts (the last packet that generates this >> frame, in this case 4) as the time position >> > of the frame? >> > >> > The file I used to test is here >> https://dl.dropboxusercontent.com/u/89678527/av_divx_24_yuv420p_mp3_44100_2_1.avi >> > >> > Thanks >> >> >> That's what best_effort_timestamp is for. See >> http://dranger.com/ffmpeg/tutorial05.html about different values of >> pts/dts. >> >> BR, >> Alex Cohn >> _______________________________________________ >> Libav-user mailing list >> [email protected] >> http://ffmpeg.org/mailman/listinfo/libav-user >> > >
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