Burr Brown PCM290x USB CODEC

Burr Brown PCM290x USB CODEC

[Edson Pereira]

Greetings,

I am in the process of implementing a small software defined radio 
receiver using the PCM2903 codec and have a question for the 
alsa-developers.

The ALSA USB-Audio interface is working very well. The audio quality of 
the chip is quite good, but the chip has a bug! The audio stream of one 
channel is delayed by one sample in respect to the other channel. This 
is drastic for the mentioned application since the phase correlation 
between channels is critical. I have contacted Burr Brown technical 
support and they have acknowledged the problem. The error is in the FIFO 
addressing hardware and is present in the ADC as well in the DAC (but in 
reversed channels).

The problem is quite easy to get around in the application, but this 
prevents the hardware interface being used with other programs (testing 
software for example). My question is: Where in the system software 
chain could a work around be implemented? In the ALSA snd-usb-audio? Or 
is there any other more appropriate place?

Thanks and best regards,

-- Edson

 


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Re: Delay channel X by one sample

[James Courtier-Dutton]

Edson Pereira wrote:
> 
> Greetings,
> 
> I am in the process of implementing a small software defined radio 
> receiver using the PCM2903 codec and have a question for the 
> alsa-developers.
> 
> The ALSA USB-Audio interface is working very well. The audio quality of 
> the chip is quite good, but the chip has a bug! The audio stream of one 
> channel is delayed by one sample in respect to the other channel. This 
> is drastic for the mentioned application since the phase correlation 
> between channels is critical. I have contacted Burr Brown technical 
> support and they have acknowledged the problem. The error is in the FIFO 
> addressing hardware and is present in the ADC as well in the DAC (but in 
> reversed channels).
> 
> The problem is quite easy to get around in the application, but this 
> prevents the hardware interface being used with other programs (testing 
> software for example). My question is: Where in the system software 
> chain could a work around be implemented? In the ALSA snd-usb-audio? Or 
> is there any other more appropriate place?
> 
> Thanks and best regards,
> 
> -- Edson
> 

I think adding this "delay channel X by one sample" feature would be a 
nice feature to add to alsa-lib. We are going to need it in order to 
support 96khz SPDIF out on the Audigy 2 cards via the P16V chip.
So, if other cards also need it, it would be good to add.

James



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