Upsampling to 176.4/192 and transcoding

[simoncn]

(28-12-2012 21:04)Alekz Wrote:  I do not think that window/packet size will be affected in a local 100/1000Mbit network. The most vulnerable is 24/192, of course, but still well within switchable Ethernet LAN limits. The bottleneck here is the disk (and the disk interface) and the CPU of the server. For example, a USB connected disk, or a server running on a busy Windows box. Then WiFi.

Yes, I agree. The current FLAC to WAV transcoding using JFLAC uses about 20% of the CPU for a 24/96 file on a 1.2 GHz ARM NAS (QNAP TS-119). This overhead should be much lower when support for using an external converter such as ffmpeg or libav is available.

[Alekz]

(28-12-2012 21:08)simoncn Wrote:  

(28-12-2012 20:54)Alekz Wrote:  Not the CPU on the NAS, but the CPU on the player. E.g. Logitech Transporter, PS Audio PerfectWave DAC or Linn DS.

I think I misunderstood your earlier comment. MinimServer already transcodes on the NAS, which removes CPU load from the player. I thought you were suggesting that this transcoding should be moved to another device to remove CPU load from the NAS. My apologies for the misunderstanding.

Sorry, I should've expressed myself more clear.

Just to clarify my point about the upsampling. Linn DS upsamples using its own CPU, my idea is to use the NAS CPU for upsampling.

[simoncn]

(28-12-2012 21:32)Alekz Wrote:  Sorry, I should've expressed myself more clear.

Just to clarify my point about the upsampling. Linn DS upsamples using its own CPU, my idea is to use the NAS CPU for upsampling.

OK, I understand your point now. The Linn DS uses an FPGA for upsampling, which in theory shouldn't load the internal CPU. Also, the Linn DS always upsamples to 352.8 or 384 kHz internally, so adding an external upsampling step won't avoid the internal upsampling step.

Despite the above, it might be interesting to try this as an experiment to find out if there's any audible difference.

[Alekz]

(28-12-2012 23:12)simoncn Wrote:  The Linn DS uses an FPGA for upsampling

Ah, didn't know that. Probably the best solution, if this is indeed true:

(28-12-2012 23:12)simoncn Wrote:  which in theory shouldn't load the internal CPU

And this is unreachable externally:

(28-12-2012 23:12)simoncn Wrote:  Linn DS always upsamples to 352.8 or 384 kHz internally

However for devices without internal upsampling it may help.