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

Paul B Mahol onemda at gmail.com
Thu Apr 25 18:56:46 EEST 2019


On 4/22/19, Paul B Mahol <onemda at gmail.com> wrote:
> On 4/22/19, Nicolas George <george at nsup.org> wrote:
>> Paul B Mahol (12019-04-21):
>>> https://dspguru.com/dsp/faqs/multirate/resampling/
>>>
>>> Resampling involves interpolation.
>>> If I do resampling with aresample and resampling with factor 2 from
>>> 44100 to 88200
>>> I can see there is still some spectrum data in highest frequencies.
>>
>> Resampling MAY involve interpolation, to enhance the subjective quality
>> of the output.
>
> It is not MAY, it MUST involve interpolation in almost any scenario.
>
>>
>>> If you haven't noticed, this is just upsampling/downsampling without
>>> lowpass.
>>> And that is not resampling in any way.
>>
>> No matter how many times you repeat it, saying that changing the sample
>> rate is not resampling will not make it true.
>
> By your flawed reasoning asetrate filter is doing resamping too.
>
>>
>>> That is just your opinion now, you need to provide technical terms
>>> to support your statements.
>>
>> I have given technical considerations: we have automatic sample rate
>> negotiation. These filter would not fit with it.
>
> If you haven't tried them, they fit well with sample rate negotiation.
> Filters change sample rate metadata by integer factor up or down.
>
>>
>> What have you provided besides your opinion and links to generic
>> considerations that do not substantiate your views?
>
> I have provided actual facts, and not opinions unlike you.
>
>>
>>> Another option to aresample filter would just confuse users.
>>
>> Less so than yet another pair of filters that do almost exactly the same
>> thing as others.
>
> No filter in libavfilter does what those filters do.
>
> And there is reason why SoX have those as separate filters and not some
> strange combination with their generic resampling effect.
>

As there appears to be no more comments or valid arguments against this
set I will apply it.


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