[LAU] hda_codec_analog 96000 sampling rate?

Clemens Ladisch clemens at ladisch.de
Tue Nov 30 07:59:54 UTC 2010

Mark Rages wrote:
> I would like to play some audio sampled at 96 kHz.  But I don't appear
> to have this enabled:
> markrages at markrages-desktop:~$ cat /proc/asound/card*/codec#0  | grep rates
>     rates [0x7f]: 8000 11025 16000 22050 32000 44100 48000
>     rates [0x60]: 44100 48000
>     rates [0x7f]: 8000 11025 16000 22050 32000 44100 48000
> But the same file lists "Codec: Analog Devices AD1986A".  I looked up
> the datasheet, and the AD1986A is able to support 96 kHz sampling with
> "Double rate audio".

"Double rate audio" is a special AC'97 mode that reuses some surround
channels to transport more samples for the two front channels.  (AC'97
doesn't have enough bandwidth for more channels at 96 kHz.)

HDA assumes that all DACs can run at the same sample rate.  However, it
looks as if this chip is just an AC'97 core that also has a HDA frontend,
so it cannot run all DACs at 96 kHz, so it completely disallows 96 kHz
when connected to a HDA controller.

(All HDA controllers would support 96 kHz playback, but as for AC'97,
only the Intel driver has double-rate support.)

> (Before you ask, I'm not trying to play music for dogs, I'm trying to
> generate FM stereo pilot tone.)
> So, what do I need to do to get 96kHz playback working?

A sound card that actually supports 96 kHz playback and that does not
filter out high frequencies in its analog output stage.

I've seen the M-Audio Audiophile 2496 advertized as being capable of
producing up to 48 kHz tones.

The Xonar D2 ran record frequencies of up to 90 kHz, but its output
filters out anything above 20 kHz.  I've heard rumors that Asus changed
this in the later Xonar models after bat owners and the HiFi Voodoo
crowd complained; try the Xonar D1 or DX.


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