[LAU] hda_codec_analog 96000 sampling rate?

Mark Rages markrages at gmail.com
Tue Nov 30 17:55:30 UTC 2010


On Tue, Nov 30, 2010 at 1:59 AM, Clemens Ladisch <clemens at ladisch.de> wrote:
> 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.)
>

Excellent answer.  Thank you.

Regards,
Mark
markrages at gmail
-- 
Mark Rages, Engineer
Midwest Telecine LLC
markrages at midwesttelecine.com


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