On 2022-06-16 01:17 pm, Michael Koch wrote:
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
remap uses framesync which by default, repeats last frame of secondary
input if primary input is still alive.
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?
For single image input, filter looping is better as it avoids file I/O
and repeat decoding of the input.
Regards,
Gyan
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