On Mon, May 8, 2017 at 3:43 PM, Paul B Mahol <one...@gmail.com> wrote:
> On 5/8/17, Muhammad Faiz <mfc...@gmail.com> wrote:
>> On Mon, May 8, 2017 at 1:22 AM, Paul B Mahol <one...@gmail.com> wrote:
>>> Signed-off-by: Paul B Mahol <one...@gmail.com>
>>> ---
>>> configure | 2 +
>>> doc/filters.texi | 30 +++
>>> libavfilter/Makefile | 1 +
>>> libavfilter/af_afir.c | 541
>>> +++++++++++++++++++++++++++++++++++++++++++++++
>>> libavfilter/allfilters.c | 1 +
>>> 5 files changed, 575 insertions(+)
>>> create mode 100644 libavfilter/af_afir.c
>>>
>>> +@item auto
>>> +Enable auto gain calculation of Impulse Response coefficients.
>>> +By default is enabled.
>>> +@end table
>>> +
>>
>> Probably, these options aren't required if algo is correct.
>
> Which ones? All of them or just last one?
IMHO:
auto isn't required. The filter should compute normalization factor correctly.
envelope will change the frequency response.
I can't see the difference between dry and wet. Basically it can be
replaced with volume filter.
length can be replaced by atrim.
Probably length and dry/wet will be OK to avoid using atrim and volume filter.
>
>>> + for (i = 0; i < s->nb_partitions; i++) {
>>> + const int coffset = i * (s->part_size + 1);
>>> +
>>> + for (n = 0; n < s->part_size; n++) {
>>> + const float cre = coeff[coffset + n].re;
>>> + const float cim = coeff[coffset + n].im;
>>> + const float tre = block[2 * n ];
>>> + const float tim = block[2 * n + 1];
>>> +
>>> + sum[2 * n ] += tre * cre - tim * cim;
>>> + sum[2 * n + 1] += tre * cim + tim * cre;
>>> + }
>>> + sum[2 * n] += block[2 * n] * coeff[coffset + n].re;
>>> + }
>>
>> This is still wrong.
>> As I read in articles, each ir partition is convoluted with different
>> data block.
>
> Hmm, could you re-check it? The code I looked doesn't do that.
Based on the article:
Consider 4096-taps FIR partitioned to 4 x 1024-taps using 2048-fft and
block size is 1024, using OLS. Negative index means zero padding
block.
fft_result(0) = fft(block(-1), block(0)) * fft(fir(0), 0)
+ fft(block(-2), block(-1)) * fft(fir(1), 0)
+ fft(block(-3), block(-2)) * fft(fir(2), 0)
+ fft(block(-4), block(-3)) * fft(fir(3), 0)
then result(0) = right half of ifft(fft_result(0))
fft_result(1) = fft(block(0), block(1)) * fft(fir(0), 0)
+ fft(block(-1), block(0)) * fft(fir(1), 0)
+ ... and so on
>
>> Test:
>>
>> aevalsrc = 'if(n, 0, 1)',
>> firequalizer =
>> delay = 0.023:
>> fixed = on:
>> wfunc = nuttall:
>> gain = 'if(between(f, 1000, 5000), -INF, 0)',
>> atrim = end_sample = 2048 [ir];
>
> The size of IR is too short. If I increase it to 12048 I get desired output.
>
Actually fir is only 2029-taps, zero padded to 2048-taps.
Using atrim = end_sample = 2048:
nb_partitions: 2
partition_size: 1024
Here second partition contains non-zero coefficients.
Using atrim = end_sample = 4096:
nb_partitions: 2
partition_size: 2048
Here second partition contains all-zero coefficients, and the
incorrect behaviour is hidden.
Thank's.
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