Convolution filtering

[tgb]

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