Julf wrote:
> "Transcoding" in this case is only reshuffling the data into the proper
> order for a PCM chain. It doesn't involve any change to the actual audio
> data. It is still a "bit perfect" chain with no audible difference, so
> from that point of view it is "just as good" as "native".
The native->DoP "shuffling" of data is usable with squeezelite doing it
on the Pi. It'll burn 10% CPU, (after the initial surge at startup to
fill the output buffer), which is fine.
It's the DSD->PCM transcode that's likely to result in less than optimal
sound output. See below .... ~80% CPU. DSD64 -> native 176k4 PCM. You're
definitely going to get the odd pop and click streaming 176k4 via USB
while "burning" ~80% CPU.
Code:
--------------------
top - 15:50:35 up 10 min, 2 users, load average: 0.81, 0.69, 0.42
Tasks: 85 total, 1 running, 84 sleeping, 0 stopped, 0 zombie
%Cpu(s): 68.4 us, 3.5 sy, 0.0 ni, 26.3 id, 0.0 wa, 0.0 hi, 1.8 si, 0.0
st
KiB Mem: 494992 total, 216980 used, 278012 free, 16092 buffers
KiB Swap: 524284 total, 0 used, 524284 free, 124348 cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
911 squeeze+ 10 -10 53272 49556 24160 S 78.8 10.0 0:20.71 squeezelite
[fedora@pidora sysconfig]$ cat /proc/asound/Amanero/stream0
Amanero Technologies Combo384 Amanero at usb-bcm2708_usb-1.2, high speed :
USB Audio
Momentary freq = 176417 Hz (0x16.0d58)
--------------------
Contrast to doing the DSD->PCM trascode on the backend and squeezelite
just decoding the native PCM streamed as flac.
Code:
--------------------
top - 15:58:03 up 18 min, 2 users, load average: 0.64, 0.58, 0.50
Tasks: 84 total, 2 running, 82 sleeping, 0 stopped, 0 zombie
%Cpu(s): 13.0 us, 7.6 sy, 0.0 ni, 0.0 id, 77.2 wa, 0.0 hi, 2.2 si, 0.0
st
KiB Mem: 494992 total, 218040 used, 276952 free, 17592 buffers
KiB Swap: 524284 total, 0 used, 524284 free, 124352 cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
930 squeeze+ 10 -10 52820 49104 24160 S 18.0 9.9 0:03.69 squeezelite
[fedora@pidora sysconfig]$ cat /proc/asound/Amanero/stream0
Amanero Technologies Combo384 Amanero at usb-bcm2708_usb-1.2, high speed :
USB Audio
Momentary freq = 176417 Hz (0x16.0d58)
--------------------
So, if you have a DAC which supports DoP it will probably be OK to use a
squeezelite built with -DDSD and the '-D' runtime flag for DoP output.
For DSD->PCM, with a DAC that isn't capable of DoP, do it on the
back-end.
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