[FFmpeg-devel] [PATCH 2/3] avfilter: add audio upsample filter

Paul B Mahol onemda at gmail.com
Fri Apr 19 13:51:52 EEST 2019

On 4/19/19, Gyan <ffmpeg at gyani.pro> wrote:
> On 19-04-2019 02:43 PM, Nicolas George wrote:
>> Paul B Mahol (12019-04-19):
>>> Users that know what they are doing will do:
>>> upsample=4,some additional filtering,alimiter=parameters,some
>>> additional filtering,downsample=4
>> Bad design. We have sample rate negotiation.
> How about a filter that can store link and/or frame props as metadata?
> This filter can be inserted before 'processing' filters.
> Then Paul's filters, inserted afterwards, can read those meta keys to
> obtain pre-process props.

There are numerous ways how oversampling/undersampling can be done.
This two filters are fundamental blocks of oversampling/undersampling.
The "some additional filtering" can be IIR or FIR lowpass, or FFT where
anything above certain range is set to 0. All mentioned solutions have
same good and bad points.
Implementing this as part of existing filter is not flexible enough
and will limit
us to only some solutions also it needs more lines of code.

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