[alsa-devel] safe support for rewind in ALSA

Kai Vehmanen kvehmanen at eca.cx
Mon Feb 1 23:10:18 CET 2010


spamming with one more mail.

On Mon, 1 Feb 2010, Kai Vehmanen wrote:

>  - at T3, application calls snd_pcm_delay() to query how many samples
>    of delay there is currently (e.g. if it write a sample to ALSA
>    PCM device now, how long before it hits the speaker)
>      - note that this is what snd_pcm_delay() is specifically for
> Anyways, the main problem is that snd_pcm_delay() accuracy is limited by
> the transfer/burst size used to move samples from main memory to the sound
> chip, _although_ the hardware _is_ able to tell the exact current position

It just occured to me that could drivers update 'runtime->delay' in their 
pointer callback...? :P And if yes, would it make sense?

Now this would fix snd_pcm_delay() right away (as it already takes 
runtime->delay into consideration). Although definitely not sure whether 
adding standardized side-effects to pointer() is a good idea...

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