Peter wroteThank you very much Skrodahl. I now understand the USB DAC thing, but reiterate that this did not happen with the same hardware setup, and Rune 0.2 beta, nor does it happen with Raspbmc or Volumio. I am not directly using a USB DAC, but a USB to S/PDIF converter, feeding a Beresford 7520 Dac, through coaxial digital input. :?:
I nominate Skrodahl as a moderator for Rune - you are very knowledgeable, and would help to lighten the load for the developers. Hope you don't mind! :oops:
I have just received my new Raspbery Pi B+, and I am now actively considering an I2S DAC, come on Gordon, we are waiting with anticipation( we, I am sure there are more than just me!)
Thanks for the appreciation Peter 🙂
I haven't been using USB -> S/PDIF -> DAC before, so I can't be certain. But to me it sounds like an overly complicated setup, one that could introduce more jitter. Now this may or may not be noticeable in the sound your system is producing, the I2S route is still a lot less complicated and more suited for the Raspberry Pi platform.
Your music files, unless they reside on the SD card, will have to be accessed in some way. Either through Wi-Fi, ethernet or a USB-connected storage. This is most likely the bottleneck when combined with a USB dac, and it seems unlikely that this will improve. The Raspberry Pi B+ could be better in that regard, it will be interesting to hear about your experiences with this board.
That said, I was able to play hires files in RuneAudio 0.2 for short periods of time. This was never stable though. With HifiBerry, my average CPU load when playing 24/192 is about 20% and the load average is somewhere between 0.5-0.7.
The tools nmon and iotop are great tools to see what's using the resources on your system though. Nmon will monitor most things, but only local disks, while iotop also monitors network shares. To install these tools:
[root@runeaudio ~]# sudo pacman -S nmon iotop
When using nmon, start it up and you'll have to press a number of keys to make it show relevant information. I like to use "v c m t k n" which will show overall health, CPU utilization, memory stats, top processes, kernel stats, network I/O. Press "h" to show what the different toggles are in nmon. Just be aware that nmon itself will utilize ~3% CPU.
I have all my music on a NAS, connected with ethernet and the network utilization in nmon will mainly show my disk activity. When playing a 24/192 track, the network usage is constant at >7mbps. A standard 16/44.1 track just gives small bursts of network traffic. All this data has to go to USB on the same bus, and you get the bottleneck with hires files. If you're connected to the network with a USB Wi-Fi dongle, it will get worse. Then you might even bump into problems with Wi-Fi network throughput.
The RuneAudio team is headed in the right direction and what they've produced in such a short time is nothing less than astounding. For some unknown reason, they're able to produce a sound quality that is way above what I've heard from similar initiatives. And from the looks of it, it is only getting better.
