Re: [LAD] JACK on Gigaport HD+ at 4800kHz (reduced channel count)

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To: Paul Davis <paul@...>
Cc: linux-audio-dev@lists.linuxaudio.org <linux-audio-dev@...>
Date: Tuesday, February 25, 2014 - 11:48 am

On Mon, Feb 24, 2014 at 07:53:58PM -0500, Paul Davis wrote:

> On Mon, Feb 24, 2014 at 6:19 PM, Fons Adriaensen wrote:

v> > In step 2, the set_*** functions are aware of the acceptable

Depends on the driver. For the hdspm driver for example, once the sample rate
is set to 96 kHz in the hw_params (and thus before any real HW configuration
is done), both snd_pcm_hw_params_get_channels_max() and ..._min() return 32
instead of 64. This depends *only* on the contents of the partially filled-in
hw_params struct, not on the actual rate used at the time. And it is the only
way user code can find out the value to use (apart from trying a zillion
combinations).

> Thus the only way to find out if a given combination of parameters is legal

That works only if the driver _lets you set the correct values_ in the first
place. If for example snd_hdspm would not work as described above, it would
be impossible to set the channel count to the correct value. Both min and max
would be 64, and snd_pcm_hw_params_set_channels() would refuse to accept the
correct value, 32.

> I only know the RME Hammerfall driver well, but in that case, where the

Wrong, at least for snd_hdspm (and I did my homework before posting this
message and the previous one).

Ciao,

--
FA

A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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Messages in current thread:
[LAD] JACK on Gigaport HD+ at 4800kHz (reduced channel count), Jörn Nettingsmeier, (Mon Feb 24, 10:35 pm)
Re: [LAD] JACK on Gigaport HD+ at 4800kHz (reduced channel c..., Jörn Nettingsmeier, (Tue Feb 25, 10:08 pm)
Re: [LAD] JACK on Gigaport HD+ at 4800kHz (reduced channel c..., Fons Adriaensen, (Tue Feb 25, 11:48 am)
Re: [LAD] JACK on Gigaport HD+ at 4800kHz (reduced channel c..., Jörn Nettingsmeier, (Tue Feb 25, 1:25 pm)