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

[Paul B Mahol]

On 4/25/19, Nicolas George <george at nsup.org> wrote:
> Hendrik Leppkes (12019-04-25):
>> The point of this kind of filtering is not that they are necessary to
>> perform filtering, because you can filter at any sample rate, but that
>> oversampling for certain filters, and downsampling after, improves
>> quality. As such, negotiation is not really equipped to handle it,
>> since its designed to deal with compatibility between filters, not
>> quality concerns, and you also wouldn't want to remove the ability to
>> filter at ordinary sample rates either.
>
> I do not want them to be available ONLY with negotiation. If people want
> to add them, fine.
>
> But when negotiation decides a conversion needs to happen somewhere,
> these treatments must be available for it, at the place where it is
> needed, which is often not known to the user.
>
> And the simplest way of achieving that is to make it an option of the
> resample filter, or even better, en option if lswr. After all, it is
> only the audio equivalent of sws_flags=neighbor.

The filter does not take sample rate as argument, but integer factor instead.
So that make it impossible to be used with lswr.