Re: [PATCH 01/10] alsa_stream: port changes made on xawtv3

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On Tue, Sep 6, 2011 at 11:42 PM, Devin Heitmueller
<dheitmueller@xxxxxxxxxxxxxx> wrote:
> One more thing worth noting before I quit for the night:
>
> What audio processor is on your WinTV USB 2 device?  The DVC-90 has an
> emp202.  Perhaps the WInTV uses a different audio processor (while
> still using an em2820 as the bridge)?  That might explain why your
> device advertises effectively only one capture rate (32), while mine
> advertises a whole range (8-48).

Just took a look at the driver code.  Seems we are calling
em28xx_analog_audio_set() even if it's not using vendor audio.  And
that function actually hard-codes the rate to 48KHz.

So here's the question:  if using snd-usb-audio, should we really be
poking at the AC97 registers at all?  It seems that doing such can
just get the audio processor state out of sync with however
snd-usb-audio set it up.  For example, the snd-usb-audio driver may
very well be configuring the audio to 32 KHz, and then we reset the
chip's state to 48Khz when we start streaming without the
snd-usb-audio driver's knowledge.

It seems like we should only be setting up the AC97 registers if it's
an AC97 audio processor *and* it's using vendor audio.

Devin

-- 
Devin J. Heitmueller - Kernel Labs
http://www.kernellabs.com
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