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Wolfson and MPD  working

superpat

Hi,

 

I installed MPD onto the provided Wolfson Audio distribution, running it headless,  console via ssh.

 

I copied the provided demo flac files to the mpd music directory.

 

I ran alsamixer and wound up the digital i/p's and outputs.

 

controlling  MPD with the GMPC client on my LInux desktop

 

96Kbps flacs are playing  superbly, output  lineout  and into my desktop audio amp and speakers,

 

Next I will set mpd to get music from my NAS using nfs, which will be interesting, as this tends load the Pi system and  cause problems with the Pi and usb dacs!

 

cheers

 

 

P

Parents

  • Hi,

     

    As promised an update on using the Wolfson Audio card,  with the music source as a NFS mounted drive  (from my NAS). using wired ethernet.

    Playing my favourite  artist, Miles Davis  2011 release Amandia at 24 / 192kbps  var bit rate up to 5857  kbps  2 chan.  flac.

     

    Firstly   the Nas / MPD  combination has always worked fine with a NFS mount on various boards. inc Beaglebone and Cubieboard, and some old x86 mini pc's.  BUT my  Rapspberry PI has ALWAYS stuttered / brief pauses (using various  USB DAC's  @ 192kbps)

     

    Despite member  shabaz's confidence that it will work with a Wolfson Audio I2s DAC.  I have to report:- 

     

    On 24 /96kbps   The raspberry Pi and Wolfson audio card work well  via the NAS.

     

    but

     

    On 24/ 192 kbps There is a very brief pause every minute or so on the audio when playing file via the NAS.  

     

    I next down loaded  a couple of the 192 kbps tracks onto the Pi's SD card. and  played them  using mpd from the card.

     

    RESULT!   perfect reproduction.  No g;itches or pauses.

     

    There is nothing else using the NAS or the internet at the time  I eas getting the pauses on MPD.  but I never have been able to use the PI, MPD and my NAS although other boards work fine.

     

     

    UMMV !!!!!

     

    regards

     

    Patrick

  • in reply to superpat

    If you're using FLAC files at 192kbps 24-bit, this is possibly over 100MB file size per song.

    So, you're talking a desired transfer rate of a few Mbps your software is streaming this in real time without buffering adequately.

    If you do get pauses it's likely to be a problem elsewhere rather than a fault of the audio board.

    You'd need to investigate the audio player software, or network, or you could write some software to temporarily transfer the music file to local storage

    before playback.

     

    EDIT: calculated the Mbps figure wrong earlier.

  • in reply to shabaz

    Hi Shabaz

     

    I think you have overlooked the point I made, in that My NAS  feeds 192kbps flac files to several other  cpu / mpd combinations,  (Cubieboard, Beaglebone black, x86 700mkz  thin clients and micro computers),  WITHOUT any glitches.

     

    It is only on the Raspberry PI,  whether with an USB DAC or the Wolfson board that I get  any pausing or glitching at 192Khz.

     

    I know it is a throughput problem, but it not straightforward  It is NOT the bandwidth of the NAS.

     

    I have spent some time on this previously with the Pi and USB dacs trying various buffer set ups for MPD, (there is an entry for this in mpd.con), but it never fixes the pauses.

     

    It appears to me to be either a Raspberry PI silicon problem,   (The ethernet on PI's is  derived from the usb channel), a firmware problem at the lowest level or a driver problem

     

    regards 

     

    Patrick

  • in reply to superpat

    As stated earlier:

    From a hardware point of view it won't have effects like skip or anything like the USB ones you've experienced. The interface is very different, and is at a determined rate with no contention from other devices like USB. It is a dedicated audio interface.

    There may well be software or driver, or other issues, but I'm afraid I can't help with that. Perhaps someone else can.

  • in reply to superpat

    I don't think I've read about anyone having usb bandwidth issues after switching from usb dacs to i2s. Shouldn't all the success hifberry users have also be true for wolfson card users in this respect?

     

    I'm not sure if you mentioned this or not, but were you able to play 24/192 files through usb dacs without glitches when the files were on the sd card?

  • in reply to superpat

    I have just played a bunch of 96 and 192 KHz/24bit tracks with the lxmusic player, average bit rate 5 111 Kbps.

    The flac files reside on another RPi that I have NFS-mounted.

    Both Pis use USB hard disks, I only have a boot partition on the SD cards.

    I experience no clicks or pauses whatsoever. When playing 192KHz tracks, the nfs server processes use ~9% CPU, at 96KHz they use less than 0.1%

     

    --

    Ragnar

Reply
  • in reply to superpat

    I have just played a bunch of 96 and 192 KHz/24bit tracks with the lxmusic player, average bit rate 5 111 Kbps.

    The flac files reside on another RPi that I have NFS-mounted.

    Both Pis use USB hard disks, I only have a boot partition on the SD cards.

    I experience no clicks or pauses whatsoever. When playing 192KHz tracks, the nfs server processes use ~9% CPU, at 96KHz they use less than 0.1%

     

    --

    Ragnar

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