Re: [PATCH] snd-via82xx: Support all sample rate conversion capabilities of DXS channels

[Takashi Iwai <tiwai@suse.de>]

At Sun, 10 Apr 2005 19:53:20 +0400,
Sergey Vlasov wrote:
> 
> Hello!
> 
> The current snd-via82xx driver does not use all capabilities of the
> DXS channels present in VIA VT8233/5/7 chips.  In particular:
> 
> - The driver only accepts sample rates which are supported by the
>   AC'97 codec; however, the controller is able to perform sample rate
>   conversion itself, therefore the codec limits do not apply (and even
>   non-standard rates can be used).
> 
> - The driver forces sample rates for all 4 DXS subdevices to be the
>   same; however, the controller has separate sample rate converters
>   for each channel.
> 
> This patch adds support for these capabilities of the VT823x
> controller to the snd-via82xx driver.  I have tested it with the ASUS
> A8V Deluxe board (VT8237 southbridge, Realtek ALC850 codec), with
> simultaneous output with different sample rates (48000, 44100, 8000,
> and some non-standard values like 44444, 12345, etc...).  The SPDIF
> output also seems to work (tested with the Sony MZ-N1 portable
> minidisc recorder).
> 
> To avoid breaking support of some other hardware which may not like
> this mode, the full DXS support is enabled only for known devices (the
> patch adds an entry for ASUS A8V Deluxe), or when the dxs_support=5
> option is used.
> 
> When using dxs_support=5, the AC'97 sample rate is locked at 48000 Hz,
> and the controller performs sample rate conversion for each DXS
> channel.  Therefore output with any sample rate between 8000 and 48000
> Hz is possible even if the codec supports only 48000 Hz (like ALC850,
> which does not support VRA).  SPDIF rate is also locked to 48000 Hz.
> 
> The patch was made for ALSA CVS version from yesterday.
> 
> Best regards,
> 	Sergey Vlasov
> 
> 
> =======================================================================
> 
> Add support for full sample rate conversion capabilities of DXS
> channels present in VIA VT8233/5/7 controllers:
> 
> - any sample rate in the 8000 ... 48000 Hz range is supported even if
>   the AC'97 codec supports only 48000 Hz output;
> 
> - different DXS channels can use different sample rates at the same
>   time (the controller performs required sample rate conversion and
>   mixing in hardware).
> 
> Signed-off-by: Sergey Vlasov <vsu@altlinux.ru>

Thanks.  I applied it to CVS.

If I understand correctly, this feature should be available on all
machines with dxs_support=4, but you added a new dxs_support entry
just to be sure not to break, right?

BTW, the SPDIF rate should be also 48k in dxs_support=4, too.
I'll fix this now...


Takashi


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