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Old 7th February 2019, 04:24 AM   #781
francolargo is offline francolargo  United States
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Join Date: Mar 2007
Location: Twin Cities, MN
I now have a RPi3B+ with Raspbian integrated into my system to see what it can do with FIR filter processing.
Good news...
Concurrently, I have the RPi doing these jobs:

1. serving music from an 8T USB hard disc using it's own Logitech Media Server process
2. converting all stored formats to flac (using SoX with no resampling)
3. Running parallel BruteFIR convolver processes for left and right channels using two 64 bit 16384 tap filter sets. (Convolver frequency adapts to original file sample rate)
4. Sending the filtered stereo signal asynchronously over ethernet out to the BBB/Hermes/Cronus, which renders I2S.

I'm watching an 'htop' representation of each core's activity while playing a 176kHz file.
CPU use is not the least bit stressed:
1. fetching and serving uses just 2-3% CPU from one core
2. flac conversion is peaking at almost 30% but is mostly in the low 20%'s of one CPU core. [This step keeps the PCM format constant running into the convolvers.]
3. Parallel BruteFIR convolutions average about 7% and peak around 10% of CPU

Conclusions:
1. RPi/Hermes/Cronus should easily be able to run a 2-way FIR crossover, and with optimization a 3-way.
2. For stereo digital room correction, left/right filter sets at 32k taps should run at 192kHz, or 16k taps at 384kHz.
3. RPi 3B+ is rather slow as a file server, running at 15-20 Mbps. But plenty fast enough for music...

Cheers,

Frank
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Old 7th February 2019, 12:59 PM   #782
miero is offline miero  Czech Republic
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Join Date: Jun 2011
Location: Prague
francolargo: Why do you convert audiodata to FLAC instead of WAV? Non-compresed data should be faster.
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BeagleBone Black with I2S, DSD and SPDIF interface (Linux driver)
http://bbb.ieero.com/
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Old 7th February 2019, 02:27 PM   #783
francolargo is offline francolargo  United States
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Join Date: Mar 2007
Location: Twin Cities, MN
Quote:
Originally Posted by miero View Post
francolargo: Why do you convert audiodata to FLAC instead of WAV? Non-compresed data should be faster.
Hi Miero! Good question. I wanted to get this system running as quickly as possible so I followed the procedure published here:

Archimago's Musings: HOWTO: Logitech Media Server + BrutefirDRC Plugin in Linux Virtual Machine (VM)

This person found that flac worked, but uncompressed 'raw' PCM didn't work in his system. Clearly, there is always room for refinement and this would be an obvious one. The plugin for LMS that runs the BruteFIR engines is in Perl, with which I have no experience. [It was written some time ago by @soundcheck]

One thing I'm doing differently is formatting the filters as text rather than as impulses. So I will mess with trying to simplify that compression step when I can. For me, first I want to learn much more about manipulating phase (using 'rePhase' by @Pos), since I'm still using my trusted IIR filters in ALSA on the BBB.

Cheers,

Frank
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Old 7th February 2019, 05:55 PM   #784
francolargo is offline francolargo  United States
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Join Date: Mar 2007
Location: Twin Cities, MN
I'm running a 96kHz file and seeing CPU use that's inconsistent with what I saw at 176kHz.

I suspect SoX may have been resampling the 176 to, perhaps, 96kHz.

At 96 kHz, one core runs at 5-7% and the second that was active at 176 is sleeping.

Conclusion is the same: The RPi 3-Hermes is going to allow us to re-imagine our system software.

Last edited by francolargo; 7th February 2019 at 05:58 PM.
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Old 17th February 2019, 09:39 AM   #785
mimsguru is offline mimsguru  South Korea
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Join Date: Feb 2007
Location: pusan
Hi,

I am assembling BBB/Hermes/Cronus with i2S-hdmi (something like Teleporter). When I play mp3 file my dac locks (44.1khz) but with no sound. I am using bbb-botic-v4-1gb.img.gz image in the http://bbb.ieero.com/index4.shtml.

what can be wrong?

Thank you in advance.

SM
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Old 21st February 2019, 08:16 AM   #786
Kanutus is offline Kanutus
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Join Date: Jun 2016
Quote:
Originally Posted by mimsguru View Post
Hi,

I am assembling BBB/Hermes/Cronus with i2S-hdmi (something like Teleporter). When I play mp3 file my dac locks (44.1khz) but with no sound. I am using bbb-botic-v4-1gb.img.gz image in the http://bbb.ieero.com/index4.shtml.

what can be wrong?

Thank you in advance.

SM
Does it work with other formats? Flac, wav, aiff?
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Old 21st February 2019, 01:39 PM   #787
pixelpusher is offline pixelpusher  United States
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Join Date: Oct 2004
Location: Minneapolis
Quote:
Originally Posted by mimsguru View Post
Hi,

I am assembling BBB/Hermes/Cronus with i2S-hdmi (something like Teleporter). When I play mp3 file my dac locks (44.1khz) but with no sound. I am using bbb-botic-v4-1gb.img.gz image in the http://bbb.ieero.com/index4.shtml.

what can be wrong?

Thank you in advance.

SM
Do you have the jumper installed on the ADC header?
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Old 22nd February 2019, 05:56 PM   #788
mimsguru is offline mimsguru  South Korea
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Join Date: Feb 2007
Location: pusan
Quote:
Originally Posted by pixelpusher View Post
Do you have the jumper installed on the ADC header?
Thank you for the reply.

No I don't have any jumper on Hermes. Do I need ADC header on Hermes installed? If I install it, what setting should I use?

SM

Last edited by mimsguru; 22nd February 2019 at 06:02 PM.
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Old 22nd February 2019, 05:58 PM   #789
mimsguru is offline mimsguru  South Korea
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Join Date: Feb 2007
Location: pusan
Quote:
Originally Posted by Kanutus View Post
Does it work with other formats? Flac, wav, aiff?
Same thing happes with Flac. 192k flac also locks fine but with no sound.

Thank you

SM
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Old 23rd February 2019, 01:47 PM   #790
pixelpusher is offline pixelpusher  United States
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Join Date: Oct 2004
Location: Minneapolis
Quote:
Originally Posted by mimsguru View Post
Thank you for the reply.

No I don't have any jumper on Hermes. Do I need ADC header on Hermes installed? If I install it, what setting should I use?

SM
I meant the ADC header on the DAC
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