Hi Vincent I believe what you're looking for is frame-accurate seeking. To achieve that you have to do input seeking instead of output seeking. The former is achieved by specifying -ss before -i in your command line, whereas you're doing the latter by specifying -ss after -i. See https://trac.ffmpeg.org/wiki/Seeking
HTH Cyril Le lun. 23 janv. 2023 à 09:15, Vincent Deconinck <vdeconi...@gmail.com> a écrit : > Hi, > > I performed more tests thinking that maybe the -f mpegts did not create > "hls-compliant" ts chunks (whatever that could mean). > So I tried creating first a full hls with the following command : > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -f hls > -hls_time 4 sample.m3u8 > This took a long time to process the full video of course, but the result > plays perfectly fine. > I then created a partial version limited to 12 seconds (=3 chunks of 4 > secs) from the same source, as follows: > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -t 12 > -f hls -hls_time 4 sample_part.m3u8 > > I performed a binary diff on the resulting ts files, and the chunks #0 and > #1 are exactly the same. > However, chunk #3 (which is the last of the "partial" version) is different > (375kB vs 392kB) : > > 1578 sample.m3u8 > 190 sample_part.m3u8 > 582424 sample_part0.ts > 764972 sample_part1.ts > 383896 sample_part2.ts > 582424 sample0.ts > 764972 sample1.ts > 401004 sample2.ts > ... > > What is the reason for that difference, and how can I make sure I generate > a valid segment for those 4 seconds ? > > Kind regards, > > Vincent > > On Fri, Jan 20, 2023 at 5:44 PM Vincent Deconinck <vdeconi...@gmail.com> > wrote: > > > Hi, > > I have thousands of files that I would like to serve as HLS streams to a > > very small number of users (3-5), without having to process them all > > upfront. So I'm looking for a way to generate single HLS chunks (as > opposed > > to a full HLS package) only when they are requested. > > My problem is the resulting stream is choppy and basically unusable. > > Here are the commands I'm using:: > > > > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -ss > 0 > > -t 4 -f mpegts cache\sample-0.ts > > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -ss > 4 > > -t 4 -f mpegts cache\sample-1.ts > > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -ss > 8 > > -t 4 -f mpegts cache\sample-2.ts > > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -ss > > 12 -t 4 -f mpegts cache\sample-3.ts > > ffmpeg -i source.ts -c:v libx264 -b:v 1000k -c:a aac -b:a 128k -g 25 -ss > > 16 -t 4 -f mpegts cache\sample-4.ts > > > > The m3u8 file is : > > > > #EXTM3U > > #EXT-X-VERSION:3 > > #EXT-X-TARGETDURATION:4 > > #EXT-X-MEDIA-SEQUENCE:0 > > #EXTINF:4.000000, > > sample-0.ts > > #EXTINF:4.000000, > > sample-1.ts > > #EXTINF:4,000000, > > sample-2.ts > > #EXTINF:4,000000, > > sample-3.ts > > #EXTINF:4,000000, > > sample-4.ts > > #EXT-X-ENDLIST > > > > What am I doing wrong ? > > > > Kind Regards, > > > > Vincent > > > _______________________________________________ > 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". > _______________________________________________ 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".
