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Old 18th February 2020, 04:09 AM   #3041
chientechnical is online now chientechnical  Viet Nam
diyAudio Member
 
Join Date: May 2016
Location: 122050, Hanoi
Quote:
Originally Posted by francolargo View Post
This is my experience as well, and I use Debian. My mpd.conf file includes:
Code:
audio_output {
        type            "alsa"
        name            "J20"
        device          "hw:0,0"        # optional
        dsd_usb         "no"
        dsd_native      "yes"
        dsd_native_type "3"
        priority        "FIFO:32"
        mixer_type      "hardware"
        period_time     "1"
#       mixer_device    "default"       # optional
#       mixer_control   "PCM"           # optional
#       mixer_index     "0"             # optional
}
I have experience manipulating asound.conf in order to run various filters, mixers and channel alignments. *You are looking at 'arecord' sources.* These will have nothing to do with output from MPD or any other player software that the OS is running. You only need to address 'recording' ports if you want to *import* a PCM stream (for example, via external USB). Then ALSA will manage the synchronous PCM stream and make the stream available in the system. For player software (like MPD) running on the linux board, the only ALSA parameter that software needs are the available *play* ports and those you can list using 'aplay -L'. Each of the listed channels will be a working input channel into ALSA. One of the channels should be 'hw:xxxx,xxxx'. You can type out the words after the colon (the 'xxxx' in my example), or you can just use the numbers 0,0 if there is no need to further process the signal. The 'hw:0,0' sends the PCM out of the ALSA system.

If you have modified asound.conf and it is not working, try this for pcm.!default:
Code:
pcm.!default {
    type plug
    slave {
     pcm "hw:0,0"
     rate "unchanged"
    }
}
In general, manipulating ALSA takes patience and study of documentation that is not at all simple nor even complete. Good luck.
I am interested in adding / extending input for (BBB+Botic): spdif, usb
An TFT LCD for display input selected and keyboard for choices input would be fine.

Last edited by chientechnical; 18th February 2020 at 04:12 AM.
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Old 18th February 2020, 03:16 PM   #3042
francolargo is offline francolargo  United States
diyAudio Member
 
Join Date: Mar 2007
Location: Twin Cities, MN
Quote:
Originally Posted by chientechnical View Post
I am interested in adding / extending input for (BBB+Botic): spdif, usb
An TFT LCD for display input selected and keyboard for choices input would be fine.
I did something similar a few years ago by adding Toslink SPDIF inputs to the system, which has increased my enjoyment in many ways.

The exact way I did it is probably not available now because the hardware I added is no longer made. Basically, it is a converter between a synchronous and asynchronous signal and it can convert either direction. I have Toslink converted to an asynchronous input to the BBB via its USB port. The BBB recognizes the asynchronous USB source and reconstructs the synchronous audio stream. In my system, it is important to run all streaming sources into ALSA because the BBB is acting as an active crossover (in addition to other tasks). Without that limitation, the Toslink signal streams could more easily bypass the BBB and connect directly to the DAC.

Your first consideration is: Why do you want/need the BBB to process the audio streams? If this really isn't necessary, you can still use BBB to manage stream routing via a digital switch (e.g. I use the TPA Otto driven from BBB GPIO output to select one of two Toslink sources). I posted information about my experiences here. If I can answer any additional questions, please ask them on that other DIY Audio thread.

In closing, I think the BBB is a great system controller because of the extensive I/O options. I started by writing bash scripts for a few tasks, but as the control options became more detailed I eventually converted to a Python command server that listens for TCP text commands from any network source. [more info here] For simple control, like DAC volume, I usually use a small command screen on my phone. For more detailed control I made a tablet version with detailed options like a) turning the DAC oversampling filters on/off and selecting the FIR filter curve, or b) selecting headphone output (no crossover) or speaker output, or c) choosing among several different crossover filter chains depending on the source of the stream (e.g. music or video?). [Please direct questions about these things to the DIYAudio thread linked above.]

The BBB can do a lot for those willing to write a bit of code!

Best,

Frank
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Old 21st February 2020, 02:45 PM   #3043
francolargo is offline francolargo  United States
diyAudio Member
 
Join Date: Mar 2007
Location: Twin Cities, MN
Quote:
Originally Posted by francolargo View Post
The exact way I did it is probably not available now because the hardware I added is no longer made.
Correction: miniDSP still sells a product that will convert SPDIF to USB. It now uses an XMOS processor and is priced around $100 US.
Quote:
Why do you want/need the BBB to process the audio streams?
...still the main question...

Off Topic: Brian or Russ, any progress on a TPA successor to the Amanero USB receiver? (Clearly, there are more than enough "average" XMOS interfaces, but where to push the envelope?)

Frank

Last edited by francolargo; 21st February 2020 at 03:02 PM.
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