[alsa-devel] Question: PCM short and long sync formats

[Omair Mohammed Abdullah]

On Monday 26 March 2012 05:38 PM, Mark Brown wrote:
> On Mon, Mar 26, 2012 at 05:37:15PM +0530, Omair Mohammed Abdullah wrote:
>> On Monday 26 March 2012 03:56 PM, Mark Brown wrote:
>
>>> I'm sorry but I still have no idea what you're talking about.  You've
>>> described PCM mode but not explained what "short frame sync" and "long
>>> frame sync" mode are.
>
>> This diagram may explain things better:
>> http://picpaste.com/pcm_fs-7dBlrkuW.png
>
> Sorry, that's not really clarifying things.  It looks like "long frame
> sync" is just I2S but presumably there's some difference?

Yes, in I2S mode, according to the spec I have, the frame sync leads the 
MSB of the data by 1 bit clock cycle. Whereas the 'long frame sync' mode 
starts with the MSB of the data.