[mythtv-users] mythmusic iec958 help

Robin Gilks g8ecj at gilks.org
Mon Jul 7 12:51:15 UTC 2008


>
> So it would seem that my sound card is doing the resampling correctly.
> However that's not the solution I thought everybody needed, because they
> all want bit-perfect audio which is not what I am getting. The only
> solution to this I can see, if you want pass-through audio to work
> correctly at any sample rate is to get a sound card that correctly sets
> the header *and* to have a processor that can accept multiple input sample
> rates.
>
> My USB sound card, while it can output digital and analog at the same
> time, doesn't appear to support an output such as ALSA:spdif - although I
> have those entries in my setup, I get no sound when I select them which
> probably means they're referring to the onboard sound card. Which is odd,
> as that doesn't have a spdif connector.. ho hum.
>
> Mark

To identify the capabilities of your soundcard, try 'aplay -l'.

If, like me your sound card will only do 48KHz then install the
alsa-plugins and use the bitrate converter with
         defaults.pcm.rate_converter "samplerate_best"
in your .asoundrc file.

With a recent kernel, you may not even need that - my Via Epia all-in-one
m/b [VIA 8237 chip] outputs to both analog and spdif at the same  time and
resamples anything that is not at 48k to suit the spdif output of the
hardware. No config files in sight!!

You might find useful info from 'aplay -L' as well and the contents of
your asound.state that alsa saves at shutdown and loads at startup (may
have a different name according to distro) also has heaps of stuff in it
that will give some clues about your hardware.

-- 
Robin Gilks




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