[FFmpeg-trac] #9278(avfilter:new): support expression in aresample

FFmpeg trac at avcodec.org
Fri Jun 4 15:03:14 EEST 2021


#9278: support expression in aresample
-------------------------------------+------------------------------------
             Reporter:  yue          |                    Owner:  (none)
                 Type:  enhancement  |                   Status:  new
             Priority:  normal       |                Component:  avfilter
              Version:  git-master   |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+------------------------------------
Changes (by yue):

 * version:  unspecified => git-master


Old description:

> aresample should take an expression rather than an integer value.
>
> suppose I want to write a graph that 1) upsample by 4x, 2) apply biquad
> filters 3)downsample by 4x
>
> currently I have to write something like "aresample=176400, equalizer
> ...,  aresample=44100". with different file formats it's very
> inconvenient.
>

> a script would work in many cases. but not all scenarios can be supported
> by scripts. It would be better if this could be supported by expression.

New description:

 aresample should take an expression rather than an integer value.

 suppose I want to write a graph that 1) upsample by 4x, 2) apply biquad
 filters 3)downsample by 4x

 currently I have to write something like "aresample=176400, equalizer ...,
 aresample=44100". with different file formats it's very inconvenient.

 a script would work in a few cases. but not all scenarios can be supported
 by scripts. It would be better if this could be supported by expression.

 it would be better if we can write "aresample='rate *4', equalizer ...,
 aresample= 'rate / 4'".

 one just need to change the integer sample rate option  definition in
 af_asample.c to using av_expr_* parsers would do the job.

--
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Ticket URL: <https://trac.ffmpeg.org/ticket/9278#comment:2>
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