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Problem with ohplayer and snd-aloop (for using brutefir convolution)
29-10-2016, 09:32 PM (This post was last modified: 30-10-2016 11:19 PM by droebbel.)
Post: #1
Problem with ohplayer and snd-aloop (for using brutefir convolution)

Thank you first of all for your amazing work! I have been using ohplayer for a while now and am very happy with it.

I have now tried to incorporate some room correction using brutefir. This was done using the loopback alsa device. The setup has been proved working on a ubuntu pc.

Hovewer, on my rpi3 with raspbian jessie I get only severely distorted sound. It's crackling, it is significantly too slow, although with correct pitch. I assume there are some kind of permanent underruns.

I first suspected brutefir, so I ruled that out by replacing it with alsaloop. The problem remained the same. Load is quite low anyway.

I then ruled out the soundcard by using the USB-soundcard that was working on the ubuntu-pc instead of the hifiberry on the rpi3. Now change.

I also tried a different playback application. Playing with aplay works fine through the loopback device, both with alsaloop as "connector" to the real soundcard and with brutefir.

As ohplayer works perfectly wen playing directly to the "real" soundcard I assume there must be some kind of problem in the interaction between ohplayer and the loopback device, but I have now run out of ideas.

I would be immensely thankful if someone could try and reproduce this problem on a raspi.

Steps to reproduce:

sudo modprobe snd_aloop

edit /etc/asound.conf and change the default soundcard to
pcm.!default  {
type hw card 1
You may leave the ctl device alone.
alsaloop -f S16_LE -c 44100 -U -C hw:Loopback,1 -P plughw:CARD=sndrpihifiberry,DEV=0
(you may have to replace soundcard and drop or change format and SR options - find the card with "aplay -L")
Restart ohplayer
turn down volume
play back audio

Thanks in advance for any ideas!
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Problem with ohplayer and snd-aloop (for using brutefir convolution) - droebbel - 29-10-2016 09:32 PM

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