[FFmpeg-user] streamselect in a realtime application

Michael Koch astroelectronic at t-online.de
Thu Jun 16 10:47:40 EEST 2022

Am 16.06.2022 um 09:33 schrieb Gyan Doshi:
> On 2022-06-16 12:45 pm, Michael Koch wrote:
>> I would like to understand why in some cases -loop 1 is required 
>> before the input files, and in some cases it can be omitted.
> -loop option is specific to the image sequence demuxer. Without it, a 
> single image input is a video stream of 1 frame length.

But why does this example work without  -loop 1? Is it an undocumented 
feature of the remap filter, that it keeps the last mapping file alive?
ffmpeg -i in.mp4 -i xmap.pgm -i ymap.pgm -lavfi [0][1][2]remap out.mp4

> You would apply loop when you need to keep alive an image sequence 
> input at a timestamp beyond its natural length, usually a fade.
> With the tpad or loop filters, this can be done inside a filtergraph 
> instead of at the demuxer level.

Which method is better, -loop 1 before the input file, or doing it in 
the filtergraph?


More information about the ffmpeg-user mailing list