Let's brainstorm..Setting up MinimServer to feed a USB DAC

[classical11]

Quote:The sound is very low-pitched and appears to play more slowly, and is also "chopped up". I am using the powered USB hub supplied by NewIT in the UK. This problem occurs without transcoding enabled.

I am using a Belkin 7 port powered hub:
http://www.amazon.com/Belkin-USB-2-0-7-P...rt+usb+hub

It comes with a 5V, 2.5A power supply.

This may be a red herring but I noticed that your hub's power supply can only give 1A so perhaps it's a power issue?

Do you feed power from the hub back into the Raspberry Pi (via a USB port on the hub)? Or do you power the Raspberry Pi independently? Do you have other devices plugged into your USB hub?

If the DAC is the only device and you power the Raspberry Pi independently, then this can't be it.

If you have other devices plugged into the hub maybe the DAC is not getting enough power from the hub.

I've read various reports from Raspberry Pi users complaining of system stability issues when using low powered hubs (or no hub at all).

Quote:Perhaps this is the cause of my sound distortion problem when using the USB hub. I am currently using 0.0 as the device. Should I be using 1,0 instead? How can I find the correct number? Is it significant whether the numbers are separated by a period or a comma?

I believe the format you are using is correct for mplayer.

The standard ALSA format for a device is hw:<card#>,<subdevice#>. mpd uses the standard ALSA format as is. mplayer requires some minor adjustments as described in the manual page:

Code:

device=<device>
                      Sets the device name.  Replace any ',' with '.' and any ':' with '=' in the ALSA device name.  For hwac3 output via  S/PDIF,  use
                      an "iec958" or "spdif" device, unless you really know how to set it correctly.

You can list your ALSA playback devices with "aplay -l". In my case, I get this:

Code:

pi@pi1 ~ $ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 1: UD110v2 [UD110v2], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

I am using 1,0 because the card ID of the DAC is 1. It's strange that it is 0 in your case because I would expect the built in analog card to always be the first. But I would have thought that you'd get absolutely no sound at all if you used an incorrect card id.

Quote:I would like to try to using mpd if I can get it running with WAV streams. Do you have any suggestions for how to do this?

I have not experimented with this yet and I am not very familiar with mpd. I will try it at some point and if I have any luck with it I will post my findings here.

Quote:I have found a noticeable improvement with wav24 transcoding of 16-bit FLAC files. With wav16 transcoding of 16-bit FLAC files, it's hard to be sure whether there's an improvement.

Looking forward to trying out transcoding to wav24 (if I can figure out how to stream it to mpd).