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Old 19th June 2017, 09:04 AM   #2321
miero is offline miero  Czech Republic
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yes, it will be a minimum install like in the old times, but with a newer software:
+ Debian 9
+ SSH
+ Botic-enabled kernel
+ ALSA (with 384kHz support)
+ MPD (with DSD-native support)
+ ympd GUI
+ basic audio tools: alsa-utils + sox
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Old 19th June 2017, 02:47 PM   #2322
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perfect! :-) ...
looking forward to install it .
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Old 19th June 2017, 05:46 PM   #2323
tods is offline tods  Germany
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Any chance you may include squeezelite and brutefir?
It always takes me some time to get squeezelite running and I really would like to give brutefir a try.
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Old 20th June 2017, 04:36 AM   #2324
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Quote:
Originally Posted by tods View Post
Any chance you may include squeezelite and brutefir?
It always takes me some time to get squeezelite running and I really would like to give brutefir a try.
I have experimented with BruteFIR on the BBB running the botic kernel. In important respects, it is less than ideal for the botic/BBB platform. This very clever platform avoids unnecessary resampling, allowing sources of different frequencies as well as DSD to play seamlessly. If you add a layer of FiR filtering, you impose the following limitations:
a) At present, you impose the frequency of the filter set on the source. It is probably possible to script a kill/restart using filter coefficients generated for the desired frequency. I started looking for different means of executing different frequency-specific FIR configurations when I hit this roadblock. It so happens that when BruteFIR is running, the parameters in /proc/asound/Botic/pcm0p/sub0/hw_params are fixed, even when no file is being played.
b) The BBB has limited processing power, such that your number of filter taps for stereo will be limited to about 2048 with 44.1/48 kHz music. For 96kHz, I recall that about 1024 taps was max. What can be accomplished with this kind of filter? You can't have much fun with bass, that's for sure. You are limited to manipulations in the mid- and high signal frequency range. 1024 might be enough to run phase equalization filters. That would perhaps be interesting but unless you know you need it, it would be a big job to undertake with no guarantee of success.
c) BruteFIR is PCM only - no DSD
d) Running BruteFIR with ALSA requires the signal to be routed through loopback channels. Getting those debugged is not trivial, and will test your patience or your familiarity with ALSA.

In summary, my opinion is that BruteFIR is a great tool, but perhaps better implemented on something more powerful than a BBB. Typical high quality filter sets for stereo audio have 16384 taps. Thus, I believe that including Brute FIR in the next distribution would add only marginally useful functionality. Especially considering the potentially daunting process of generating filter sets.

If you want to mess with FIR on the BBB, there is a simpler alternative for stereo sources. SoX has a FIR convolver and it is easier to get that running than BruteFIR. For example, I use the SoX convolver for SPDIF inputs in which the source frequency is 100% constant. Let me know if you would like some example script code in python.

Regards,

Frank
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Old 20th June 2017, 09:25 AM   #2325
tods is offline tods  Germany
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Hi Frank,

thanks for this explanation.
There are distributions for the Raspi using BruteFir, so I thought the BBB should work as well. Especially as the BBB can handle multichannel I2S.
I planned to use two of them to handle crossover and room correction for subwoofers. But according to your explanation, that might not be a good idea.

Not sure what I am going to try next...

Thanks
and best regards

Torsten
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Old 20th June 2017, 11:16 AM   #2326
miero is offline miero  Czech Republic
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I'm just guessing, but IIR filters might be usable in this case.
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Old 20th June 2017, 11:28 AM   #2327
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Quote:
Originally Posted by tods View Post
Not sure what I am going to try next...
Hi Torsten,

My system sounds fine using IIR crossover filters. I suggest Linkwitz-Riley 4th order alignments. There is a thread concerning this where others have helped me and I have tried to help others. Messing with ALSA is not always fun, so having a place to ask specific questions is useful.

LADSPA filters for digital crossovers on the BBB

The filters run in ALSA and processing does not interfere with botic's management of sample rates. Both IIR and FIR filters have sonic disadvantages - FIR can cause 'pre-ringing', while IIR can disrupt phase. With separate woofers, you can correct phase somewhat by changing the time alignment to those drivers (or moving the boxes).

Unfortunately, the LADSPA filters do not work on DSD sources. If you have questions I suggest asking on the LADSPA filter thread.

All the best,

Frank

Last edited by francolargo; 20th June 2017 at 11:48 AM.
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Old 20th June 2017, 10:07 PM   #2328
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Hi miero. I've been planning to use BBB/botic with a DSD 'no-dac' but people still report loud 'pop' noises with switching to DSD, changing rates etc. The issue appears to be Alsa related and doing some research on the issue I stumbled across this patch and wondered if it's been, or should be, applied to Botic?

[PATCH] ALSA: usb-audio: Eliminate noise at the start of DSD playback. — ALSA Devel

Tha patch notes refer a lot to USB DAC connection but I think that is just because of the reference framework of the developer and if Alsa is failing to produce proper DSD silence patterns it will apply beyond USB implementations.

I don't think the DSD pop affects ESS DACs because of the way they operate.
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Old 20th June 2017, 10:29 PM   #2329
miero is offline miero  Czech Republic
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ALSA in Debian 9.0 contains support for silence generating DSD patterns.

Also in the previous version Botic could be configured to control ES9018 via I2C and trigger mute if needed.
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Old 20th June 2017, 10:58 PM   #2330
twluke is offline twluke  Japan
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Quote:
Originally Posted by miero View Post
Also in the previous version Botic could be configured to control ES9018 via I2C and trigger mute if needed.
I hope this could be 'As in the previous version ...".

Regards,
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