On Mon, Jun 15, 2020 at 4:25 PM Peter <pdc.cse+ffm...@gmail.com> wrote:
> > > On Mon, Jun 15, 2020 at 3:20 PM Gyan Doshi <ffm...@gyani.pro> wrote: > >> >> >> On 15-06-2020 07:38 am, Peter wrote: >> > Hello, >> > >> > I'm trying to create a video from a series of PNG frames and then loop >> > specific frames using the loop filter. It is giving me a bit of trouble. >> > Ffmpeg is dropping a single frame somewhere and I'm not sure why that >> is. >> > Would appreciate it if someone could take a look. >> > >> > Essentially I have a concat demuxer input with 32 frames. I would like >> to >> > repeat frame #16 104 times. And repeat frame #34 14 times. 32 input >> frames >> > + 104 + 14 = 150 frames. At 30fps, my intention is to produce a 5 second >> > video with exactly 150 frames. But I can only manage to produce 149 >> frames. >> >> Can you identify which frame is missing? >> >> Gyan > > > I'm pretty sure that the last frame is being dropped. That is, the loop of > the last frame is missing. Meaning that this section of the filtergraph is > only producing 13 extra frames. > > [layer_1]loop=loop=14:start=32:size=1, > > just some extra confirmation: > > - changing "start=32" to "start=31" produces the exact same 149 frame > video. > - changing "loop=14" to "loop=15" produces a correct 150 frame video > (although this seems wrong to me as I would expect a 151 frame video given > these parameters) > > > > I am even MORE confident that there is some ffmpeg aspect that is affecting my results that I am not aware of as two different techniques have produced the exact same unexpected output. I tried it another way, using split with trim filter to extract specific frames, then looping them individually, then concat filter to merge the video streams. This alternative approach still produces a 149 frame file. The exact same binary file as the above (according to "diff -b"). [0]null[layer_0]; [1]null[layer_1]; [layer_1]split=4[s1][s2][s3][s4]; [s1]trim=start_frame=0:end_frame=15,setpts=expr=PTS-STARTPTS[l1]; [s2]trim=start_frame=15:end_frame=16,setpts=expr=PTS-STARTPTS,loop=loop=104:start=0:size=1[l2]; [s3]trim=start_frame=16:end_frame=31,setpts=expr=PTS-STARTPTS[l3]; [s4]trim=start_frame=31:end_frame=32,setpts=expr=PTS-STARTPTS,loop=loop=14:start=0:size=1[l4]; [l1][l2][l3][l4]concat=n=4,setpts=expr='N/(30*TB)'[layer_1_loopedFrames]; [layer_0]fps=fps=30.000000[layer_0_fps]; [layer_1_loopedFrames]fps=fps=30.000000[layer_1_loopedFrames_fps]; [layer_0_fps][layer_1_loopedFrames_fps]overlay=x=0.0:y=0.0:format=auto[overlay_all] And, as previously mentioned, if I repeat the last frame one more time than necessary, it produces a correct 150 frame output. [0]null[layer_0]; [1]null[layer_1]; [layer_1]split=4[s1][s2][s3][s4]; [s1]trim=start_frame=0:end_frame=15,setpts=expr=PTS-STARTPTS[l1]; [s2]trim=start_frame=15:end_frame=16,setpts=expr=PTS-STARTPTS,loop=loop=104:start=0:size=1[l2]; [s3]trim=start_frame=16:end_frame=31,setpts=expr=PTS-STARTPTS[l3]; [s4]trim=start_frame=31:end_frame=32,setpts=expr=PTS-STARTPTS,loop=loop=15:start=0:size=1[l4]; [l1][l2][l3][l4]concat=n=4,setpts=expr='N/(30*TB)'[layer_1_loopedFrames]; [layer_0]fps=fps=30.000000[layer_0_fps]; [layer_1_loopedFrames]fps=fps=30.000000[layer_1_loopedFrames_fps]; [layer_0_fps][layer_1_loopedFrames_fps]overlay=x=0.0:y=0.0:format=auto[overlay_all] Notice, the loop of 15 (should be 14) in the [s4]...[l4] filterchain Different approach, same unexpected/wrong output. Can anyone tell me what I'm missing here? _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email ffmpeg-user-requ...@ffmpeg.org with subject "unsubscribe".
