BBB - Audio notes

RE: BBB - Audio notes

morgaine — Tue, 03 Dec 2013 00:40:16 GMT

shabaz wrote:

I tried to play the same audio file but directing to HDMI:

ffmpeg -i test2.mp3 -f alsa "default:CARD=Black" -re -vol 20

It did work, but the current software build has known HDMI audio issues and it was noticeable - it didn't sound great always. Not noise, but some other digital effect.

I've just tried this with BBB running Debian on the 3.8.13-bone30 kernel, with the same bad result as yourself --- there's a pretty nasty distortion effect of some kind received on HDMI audio. It's not overload clipping, as the output level is fairly low at all -vol settings. (In case it may be relevant, there was only a VT console displaying on HDMI, no X11.) Although the audio is still identifiable as music, the quality is not usable in this state.

I haven't yet eliminated the possibility of ground continuity problems between BBB and the HDMI receiver, which I have seen mentioned as a cause of audio problems for BBB.

In contrast, USB audio works perfectly for me on the BBB into one of these cheap unbranded USB Sound Boxes, which identifies as "Microdia A56AK". My magic incantation for ffmpeg into this device is:

ffmpeg -i INPUTFILE.mp3 -f alsa "default:CARD=U0xc450x1158" -re -vol 128

I'd be interested to hear if anyone manages to get undistorted audio from BBB over HDMI.

Morgaine.

RE: BBB - Audio notes

cstiegman123 — Thu, 18 Jul 2013 14:43:44 GMT

Hello Shabaz-

Thank you so much for posting your article on USB Audio with respect to Beaglebone Black. I was wondering if I could ask a few additional questions regarding this topic. Looking to use Beaglebone Black for audio purposes.

On a high level, here is what I am looking for:

- USB audio class version supported by BB Black -> Audio class 1.0 or Audio class 2.0 or both?

- USB audio streams supported -> audio OUT only (playback) or audio IN only (recording) or both IN & OUT (simultaneous recording and playback)

- USB audio clocking system supported -> Synchronous or Asynchronous or Adaptive or some combination of these 3 types

- Digital audio bit resolution supported -> 16 bit only, 24 bit only or both 16 & 24 bit support

- USB audio sampling rate support -> 32k/44..1k/48k/88.2k/96k etc.

- USB audio configuration applications available on the BB Black platform -> Something similar to Audio MIDI Setup on Mac or Windows Sound utility.

- Audio and MIDI applications available on the BB Black platform etc..

Thank you in advance for whatever light you can shed on these inquiries.

Best Regards,

Craig

RE: BBB - Audio notes

Former Member — Thu, 20 Jun 2013 07:15:56 GMT

All your articles are very helpful, and they provide great insights for people who are looking for a starting point. Thank you for putting so much time and effort in them. With the help of this article (I simply used the pins you mentioned), I managed to get (very low quality, due to long wires, passive I / V output, and cheap perf-board connections) sound (mp3 play with ffmpeg) from my BBB using a 74HCT74 (to divide the bit-clock by 4) and a TDA1543 (16-bit I2S DAC @ 9MHz). I'm going to print a suitable PCB and try again with opamps at the outputs soon, and hopefully have cheap and usefull audio output for my portable SDR project. Thanks again [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-94b0ad68-90ee-4f4b-8275-d6110db5e8ce/contentimage_5F00_1.png:16:16]