Changing the resolution breaks the force_key_frame segmentation with timestamps. :/ Is there some way to do it?
On 2/16/19 11:22 AM, Nick wrote: > Thanks for the answer. > But I want to do the same thing like the person from the mailing list. > I want that ffmpeg cuts the video in specific segments for DASH with > variable durations. > I want to extract this information and use it to cut the video again > using different qualities. > I could use the -map command for directly encoding different qualities > but I want to outsource the workload. > I want to be sure that everything is aligned. > > The one person from the mailing list said: > >> In this particular case, you can easily work around the floating point >> rounding issues, since the rounding behaviour of -force_key_frames is >> specified: "more precisely at the first frames after each specified time". >> You just have to make sure your timestamps are rounded down. For example, >> with 24000/1001 FPS: 4.21 4.25 4.30* 4.34 4.38, you need to write 4.29, not >> 4.30, but you can also write any value between 4.25425 and the actual >> 4.295958333. (4.25+4.30)/2 = 4.275 should always work. > This looks a bit like a workaround to me. Frame numbers look more > precise for me. > I do not understand why frame numbers should not be aligned except the > frame rate is changing. > > On 2/16/19 8:52 AM, Gyan wrote: >> >> On 16-02-2019 05:03 AM, Nick wrote: >>> Hi, >>> why was the "Modified force_key_frames option to accept frame numbers" >>> (2014) declined? >>> >>>> https://ffmpeg.org/pipermail/ffmpeg-devel/2014-November/165167.html >>> You can even specify frame numbers in the current ffmpeg version using: >>>> -force_key_frames expr:gte(n,n_forced*96) >>> Using a framerate of 24 means a keyframe every 4s. >>> I think it is very useful to have something like >>> >>>> /force_key_frames n:0,25,50,75,100/ >> For a regular pattern like that one, you can already use >> >> -force_key_frames expr:not(mod(n,25)) >> >> Expressions are be evaluated using the interface documented at >> https://ffmpeg.org/ffmpeg-utils.html#Expression-Evaluation >> >> >> Gyan >> _______________________________________________ >> ffmpeg-user mailing list >> [email protected] >> http://ffmpeg.org/mailman/listinfo/ffmpeg-user >> >> To unsubscribe, visit link above, or email >> [email protected] with subject "unsubscribe". > _______________________________________________ > ffmpeg-user mailing list > [email protected] > http://ffmpeg.org/mailman/listinfo/ffmpeg-user > > To unsubscribe, visit link above, or email > [email protected] with subject "unsubscribe". _______________________________________________ ffmpeg-user mailing list [email protected] http://ffmpeg.org/mailman/listinfo/ffmpeg-user To unsubscribe, visit link above, or email [email protected] with subject "unsubscribe".
