[FFmpeg-user] Framerate automatically increased while cropping

[Ulf Zibis]

Am 23.08.21 um 07:15 schrieb Adam Nielsen via ffmpeg-user:
>> why is the framerate automatically changed here from 29.98 fps to 120
>> fps, and how can I prevent from this ?
>>
>>     Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 2508 kb/s, 29.98 fps, 120 tbr, 90k tbn, 2k tbc (default)
>  From what I can find, "tbr" is the target framerate the media is
> indicating it wants.
This is interesting. Thanks for the info. I would interpret this as meant for the playback of the video, e.g. for the ffplay. And why isn't it abreviated with "tfr" ?
>    So ffmpeg is just respecting that value.
With that contract I do hard, because in result I get a video with 15 % more bitrate and with lower quality, q=33.0 instead q=29.0. So I think, ffmpeg should retain the original bitrate and just propagate the tbr to be interpreted by the player.

> I guess you could use the -r option to override this and force a
> specific framerate if you want something different?
Yes, this works fine. But I would appreciate, if I could use something like -r=inputrate or --keep_framerate
>    Or you could fix the metadata in the source file to have the correct target framerate to begin with.

Hm, this is not really convenient.

-Ulf