[alsa-devel] Via VT82xx VT1708 ICE1724HT and higher sample rate/bit depth files through SPDIF

[Demian Martin]

I have several problems trying to play files higher than 48000 KHz and with
bit depth of 24 bits. I submitted this to the users and got a resounding
silence.

 

First- sample rate

Even though the documents claim that it will play at 176.4 KHz and 192KHz
whenever I play a file at these rates it down converts to ½ the rate (88200
and 96000). I tested this with the ICE1724HT (Juli@) which has almost the
same core, I never could get 176.4KHz at the SPDIF output. I confirmed that
the ICE1724 will play the file at 176.4KHz in Windows so its not a hardware
limitation. I tried to do the same with the VT1708 (on a Via CX700  chipset)
and the Windows driver wouldn’t let me at anything other than 48000. 

 

Second, the only way I can get the 24 bit files out in a form that the card
can play is to pass them through dmix. But I need to reconfigure dmix for
each sample rate. And I’m not convinced that it isn’t resampling twice, both
at the input and the output. Or how to configure the buffers etc. to prevent
underruns even when the only conversion is to pass a 24 bit file to the
card.

 

I’m trying to build a high quality music server that will pass the files to
either the internal or an external DAC at the bit depth and sample rate they
were recorded at. I have tried to understand the various plugs and settings
but it seems they are all focused on mixing various streams. I want to send
the files unmixed to the output. I can’t figure out what set of plugs and
settings in asound.conf would enable this.