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Convolution filtering
16-02-2020, 22:49
Post: #11
RE: Convolution filtering
What should I use if I want to set the following:

16Bit FLAC to 16bit WAV

and

24Bit FLAC to 24bit WAV

Thanks!
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16-02-2020, 23:01
Post: #12
RE: Convolution filtering
Please read my previous post.
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17-02-2020, 00:53
Post: #13
RE: Convolution filtering
(16-02-2020 23:01)simoncn Wrote:  Please read my previous post.

I did. It is not clear to me. That is why I am asking for a clear example.
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17-02-2020, 01:18
Post: #14
RE: Convolution filtering
(17-02-2020 00:53)rompolompo Wrote:  
(16-02-2020 23:01)simoncn Wrote:  Please read my previous post.

I did. It is not clear to me. That is why I am asking for a clear example.

As per Simons post as follows

The setting

flac:wav;

transcodes
16-bit FLAC files to 16-bit WAV
and
24-bit FLAC files to 24-bit WAV
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17-02-2020, 03:51
Post: #15
RE: Convolution filtering
I was missing this. All looks ok now. Thank you both.
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04-05-2020, 07:45
Post: #16
RE: Convolution filtering
Hi,
for the noob like me ;-) please find here info regarding the implementation of convol to Minim (Minim is on my DS415+, Synology NAS).
I found a bit tricky to put the right strings in stream.converter & stream.options to get no "red warning" :-)

1st : I had to upgrade ffmpeg, because I kept having a red warning in the stream.options line : Minim (or ffmpeg) could not find the way to the folder where the convol .wav file was...
According to few posts on forums, the basic ffmpeg in the Syno is "very basic".
Thus, I went there => https://synocommunity.com/package/ffmpeg
You download the right version according to the proc of your Syno => manual install => done.

Then, in Minim interface I put :
=> stream.converter => /var/packages/ffmpeg/target/bin/ffmpeg
when I left "ffmpeg" only, I still got a red warning

=> stream.options => convOut=-i /volume2/Data/Convol/impulse12.wav -lavfi afir=gtype=gn
"/volume2/Data/Convol/impulse12.wav" is complete path to the convol file ; this file is not the music folder scanned by Minim, of course.
"-lavfi afir=gtype=gn" is to avoid clipping according to "experts" (I'm not :-) )

=> stream.transcode => flac:wav24;192,dsf:wav24;192,aac:wav24;192,mp4:wav24;192
this is the string I used b4 implementing the convol. No change : all files transcoded to wav24;192 (except my mp3s)

Works perfectly. Convol requires no extra CPU (I expected "more"). Great.

Simoncn,
you mentionned b4 that having 1 convol file for each sample rate is "theoretically better" than only 1.
Is it something you found when listening tests ?
Does someone find a improvement with x convol files instead of only 1 ?
In my case, as a start, I used a unique .wav file (24-192). It works... so far I did not noticed anything bad when I listen other samples rate files than 24-192...

As mentioned in this thread => http://forum.minimserver.com/showthread....4#pid36514
Convolution leads to gaps... BUT no big deal, according to my rough tests & understanding, you end up with gaps only if the number of taps used to generate the convolution file is too high (I use rePhase to generate the .wav file).
Above 131072taps => gaps. The higher the number of taps, bigger is the gap.
At 131072taps : fine for me. Gaps are tiny, thus I found it si so close to gapless that I kept this convol file @ 131072.
Below 131072taps, I expect the gap to be even smaller, thus roughly gapless.

Thanks to you Simon for your job & this amazing powerful & lightweight tool, Minim :-)
BRgds

Optical LAN & hifi setup : https://www.dropbox.com/s/757c488ovo1zw6...0.pdf?dl=0
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04-05-2020, 09:44
Post: #17
RE: Convolution filtering
Please don't make similar posts to multiple threads. If people respond in both places, it makes the discussion very hard to follow. To prevent this happening, it is unfortunately necessary for me to temporarily close the other thread to further posts.
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04-05-2020, 10:02
Post: #18
RE: Convolution filtering
The convolution file must have the same sample rate as the file being transcoded. If you provide a convolution file with a different sample rate, FFmpeg resamples it internally before using it for convolution. I would expect slightly better results from avoiding this resampling but I haven't done any tests to compare.

The special options to reduce the gap (mentioned in your other post) compensate for the convolved output being slightly time delayed compared with the input. Assuming there is a delay of 32768 samples, the input is padded with 32768 samples of silence at the end and the output has 32768 samples removed from the beginning. The remainder of the file is processed unchanged, so audio quality is not affected. I don't know whether 32768 is always the correct value to use.
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04-05-2020, 12:37
Post: #19
RE: Convolution filtering
(04-05-2020 07:45)tgb Wrote:  for the noob like me ;-) please find here info regarding the implementation of convol to Minim (Minim is on my DS415+, Synology NAS).
Please note that your DS415+ (Intel Atom CPU) will struggle as you implement higher taps and with higher resolution. Strongly recommend getting a decent Intel NUC and run with Linux and MinimServer.

p/s have DS414 which stores music and a separate Intel NUC
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04-05-2020, 14:02
Post: #20
RE: Convolution filtering
(04-05-2020 12:37)Snoopy08 Wrote:  Please note that your DS415+ (Intel Atom CPU) will struggle as you implement higher taps and with higher resolution.
Absolutly not.
Like you, I "expected" some more/much more CPU usage for convolution. But finally : none.
I had only 1.2% CPU usage linked to the use a very big convolution file. With a current size file (1Mo), no extra CPU.
For my setup (music storage > convol&transcoding > streaming), the NAS manage to do it all, with nearly no CPU usage. Thus, no need to add a NUC in that case.
Rgds

Optical LAN & hifi setup : https://www.dropbox.com/s/757c488ovo1zw6...0.pdf?dl=0
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