Friendly ping. Would greatly appreciate some input on this. Thanks, Vignesh
On Fri, Jan 22, 2021 at 3:35 PM Vignesh Ravichandran < vignesh.ravichandra...@gmail.com> wrote: > I am trying to create a video by stitching multiple HLS segments (.ts > files) together based on a start time and end time. Basically, create a > video of a particular timeline in the HLS stream. > > My setup has a camera pointing to a monitor that displays the system clock > (The camera control and the ffmpeg command run, is on the same system). > The frame rate of the camera is not constant but is capped at 25 FPS. The > frames captured from the camera are passed on to the following ffmpeg > command: > ``` > /usr/bin/ffmpeg -vaapi_device /dev/dri/renderD128 -y -v 9 -loglevel 99 -f > rawvideo -vcodec rawvideo -s 1920x1200 -pix_fmt uyvy422 -i - -an -r 25 > -vcodec h264_vaapi -vf format=nv12,hwupload -force_key_frames > expr:gte(t,n_forced*1) -f hls -hls_list_size 10080 -hls_time 10 -hls_flags > delete_segments -hls_flags second_level_segment_index -hls_flags > +append_list+discont_start+program_date_time -strftime 1 -strftime_mkdir 1 > -hls_segment_filename %Y/%m/%d/%%04d.ts playlist.m3u8 > ``` > > I parse the playlist file created and then pick up a set of .ts files that > lie between the given start and end time. This is done by comparing the > “#EXT-X-PROGRAM-DATE-TIME” value of each file in the playlist. Then, I > stitch these files together and trim to produce the final output video file. > > Problem Encountered: > I noticed that the “#EXT-X-PROGRAM-DATE-TIME” value in the playlist file > for most segments and the system time shown in the start (00:00:00) of the > corresponding segment video is different. The “#EXT-X-PROGRAM-DATE-TIME” is > behind. For example, for below entry: > ``` > #EXTINF:10.000000, > #EXT-X-PROGRAM-DATE-TIME:2021-01-21T23:17:05.000+1100 > 2021/01/21/0085.ts > ``` > the value shown on the system clock in the video is > "2021-01-21T23:18:12.000+1100" which is more than a minute ahead. > This causes the final video created to contain incorrect timeline from the > stream. > > My observation and conclusion: > Since the FPS of the camera is not constant and can vary between 0 to 25, > ffmpeg would have to duplicate frames when the input FPS drops below 25. > But I don’t see any mention of this happening in the logs. So I think > ffmpeg is filling in the current segment with frames outside the segment > duration i.e., with frames which are supposed to be in the next segment. > And the experiment mentioned above verifies it. > > Looking at the code, the “do_video_out” function in “ffmpeg.c” file has > logic to duplicate frames if needed. But not sure why this is not > happening. Would greatly appreciate some help in debugging and resolving > this issue. I have also attached the log file from my test here. > > Thanks, > Vignesh > > ffmpeg.log > <https://drive.google.com/file/d/1FDx2LzVNksl2w-6fz9ShC7vvbrhEXsQv/view?usp=drive_web> > > _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
