[FFmpeg-user] How can I force a 360kHz time base?

[Paul B Mahol]

Ever looked at (a)settb filter?

On Fri, Feb 26, 2021 at 9:38 PM Mark Filipak (ffmpeg) <markfilipak at bog.us>
wrote:

> How can I force ffmpeg to use a 360kHz time base? (I spent 1/2 day
> searching.)
>
> Thanks!
> Mark.
>
>
> With a 1kHz time base:
> 65535 = largest 16-bit integer.
> 0:01:05.535 = longest running time for 16-bit integer with 1kHz time base..
> Conclusion: FFmpeg cannot be using 16-bit integers.
> 16777215 = largest 24-bit integer.
> 4:39:37.215 = longest running time for 24-bit integer with 1kHz time base.
> Conclusion: FFmpeg could use 24-bit integers if time base is capped at
> 1kHz.
>
> With a 90kHz time base:
> 16777215 = largest 24-bit integer.
> 00:03:06.4135 = longest running time for 24-bit integer with 90kHz time
> base.
> Conclusion: FFmpeg cannot be using 24-bit integers.
> 4294967295 = largest 32-bit integer.
> 13:15:21.8588[3..] = longest running time for 32-bit integer with 90kHz
> time base.
> 24/1.001fps ==> deltaPTS = 3753.75.
> 24fps ==> deltaPTS = 3750.
> 25fps ==> deltaPTS = 3600.
> 30/1.001fps ==> deltaPTS = 3003.
> 30fps ==> deltaPTS = 3000.
> 50fps ==> deltaPTS = 1875.
> 60/1.001fps ==> deltaPTS = 1501.5.
> 60fps ==> deltaPTS = 1500.
> Conclusion: Since 24/1.001fps requires rounding, a 90kHz time base is not
> optimal.
>
> With a 360kHz time base:
> 4294967295 = largest 32-bit integer.
> 3:18:50.464708[3..] = longest running time for 32-bit integer with 360kHz
> time base.
> 24/1.001fps ==> deltaPTS = 15015.
> 24fps ==> deltaPTS = 15000.
> 25fps ==> deltaPTS = 14400.
> 30/1.001fps ==> deltaPTS = 12012.
> 30fps ==> deltaPTS = 12000.
> 50fps ==> deltaPTS = 7200.
> 60/1.001fps ==> deltaPTS = 6006.
> 60fps ==> deltaPTS = 6000.
> 100fps ==> deltaPTS = 3600.
> 120/1.001fps ==> deltaPTS = 3003.
> 120fps ==> deltaPTS = 3000.
> Conclusion: A 360kHz time base is optimal, even for 100fps & 120fps.
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