[FFmpeg-devel] [DECISION] scaletempo filter

[Paul B Mahol]

On 5/7/19, Paul B Mahol <onemda at gmail.com> wrote:
> On 5/6/19, Marton Balint <cus at passwd.hu> wrote:
>>
>>
>> On Mon, 6 May 2019, Marton Balint wrote:
>>
>>>
>>>
>>> On Mon, 6 May 2019, Paul B Mahol wrote:
>>>
>>>> On 5/6/19, Marton Balint <cus at passwd.hu> wrote:
>>>>>
>>>>>
>>>>> On Sat, 4 May 2019, John Warburton wrote:
>>>>>
>>>>>> On Sat, May 4, 2019 at 3:34 PM Nicolas George <george at nsup.org>
>>>>>> wrote:
>>>>>>
>>>>>>> John Warburton (12019-05-04):
>>>>>>>
>>>>>>> > Is there a patch I can use to test scaletempo to compare it
>>>>>>> > against
>>>>>>> atempo?
>>>>>>> > It'll be no trouble to do that with the normal audio that is
>>>>>>> time-adjusted
>>>>>>> > on that radio station. It may be that its increased quality is
>>>>>>> > most
>>>>>>>
>>>>>>> John, we would appreciate your input about whether these new
>>>>>>> implementation of atempo is superior or equal to the existing one
>>>>>>> with
>>>>>>> regard to your needs.
>>>>>
>>>>> I tested scaletempo (with default settings) and it is definitely worse
>>>>> than atempo for small scaling factors like 25/24.
>>>>>
>>>>
>>>> Have you tried other scaling factors?
>>>> How you done testing?
>>>
>>> Simple hearing tests. I hear audible artifacts (a kind of audio
>>> stuttering) with scaletempo. Here are some files where it is noticable:
>>>
>>> fate-suite/delphine-cin/LOGO-partial.CIN
>>> fate-suite/real/spygames-2MB.rmvb
>>> fate-suite/wmapro/Beethovens_9th-1_small.wma
>>> fate-suite/dts/dts.ts
>>>
>>> The last one is noticable even with 2x scaling.
>>
>> Another one, audible with any (0.5, ~1, 2) scaling:
>>
>> fate-suite/paf/hod1-partial.paf
>>
>
> OK, vote and patch dropped.
>
> Even by using basically same algorithm, it is very slow to get same
> quality because does not use FFT for cross-correlation.
>

I got into possession of code that is better than atempo for very
small scale factors (0.5).

So I gonna write new filter which would also be able to change both
tempo and pitch at same time.