Hello everybody, I am currently trying to create an HLS live stream from a video input. I want to output various qualities streams for adaptive HLS. For the moment, I have succeeded to output various qualities streams but they are not saved synchronously. Using the following command, there is a delay between the "high" and "low" output streams.
ffmpeg -re -f decklink -i 'UltraStudio Mini Recorder@11' \ -force_key_frames "expr:gte(t,n_forced*3)" -vcodec libx264 -r 1 -crf 18 -profile:v baseline -maxrate 256k -bufsize 480k -pix_fmt yuv420p \ -f segment -segment_list low/demo.m3u8 -segment_list_flags +live -segment_time 3 -segment_time_delta 0.05 low/demo%03d.ts \ -force_key_frames "expr:gte(t,n_forced*3)" -threads 3 -vcodec libx264 -r 25 -crf 18 -profile:v main -maxrate 1000k -bufsize 1835k -pix_fmt yuv420p \ -f segment -segment_list high/demo.m3u8 -segment_list_flags +live -segment_time 3 -segment_time_delta 0.05 high/demo%03d.ts What does the command do ? 1) Gets an input stream from a BMD capture device 2) Saves a high quality HLS stream (25fps / main profile / keyframe every 3 sec / constant segment duration 3 sec) 3) Saves a low quality HLS stream (1fps / baseline profile / keyframe every 3 sec / constant segment duration 3 sec) Lets say, the 15 first segments of the "high" output are saved, and only after that, the segments of the "low" output are saved. For instance, my directories will contain : ./high/demo001.ts - ./low/demo001.ts ./high/demo002.ts ./high/demo003.ts ./high/demo004.ts ... ./high/demo014.ts ./high/demo015.ts - ./low/demo001.ts ./high/demo016.ts - ./low/demo002.ts ./high/demo017.ts - ./low/demo003.ts ./high/demo018.ts - ./low/demo004.ts From what I have observed, the delay is due to the framerate. The lower framerate (-r 1) takes more time to start. When I tried with a higher framerate (-r 10), both « slow » and « high » qualities were created simultaneously. As if FFMPEG required to fill in a cache before delivering the video segments. Any idea what could I change to prevent the delay with very low framerate ? Thank you for your help. Arnaud. Arnaud WIJNS ULB Podcast | Informaticien http://podcast.ulb.ac.be <http://podcast.ulb.ac.be/> Téléphone : 02/650.29.26 Email : arnaud.wi...@ulb.ac.be <mailto:arnaud.wi...@ulb.ac.be> Université libre de Bruxelles Campus du Solbosch - CP 160/26 Avenue F.D. Roosevelt, 50 - 1050 Ixelles _______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user
