[alsa-devel] XRUN handling

[Jaroslav Kysela]

On Mon, 19 Jul 2010, Jaroslav Kysela wrote:

> On Wed, 14 Jul 2010, melwyn lobo wrote:
>
>> Another query, if setting runtime parameters like:
>> runtime->silence_threshold = runtime->boundary;
>> runtime->silence_size = runtime->boundary;
>> runtime->stop_threshold = runtime->boundary;
>>
>> Also to avoid the bug in snd_pcm_playback_silence()  i.e.,
>> snd_BUG_ON(frames > runtime->buffer_size),
>> I have added a tweak in the driver IRQ handler:
>
> This patch might fix this problem:
>
> diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
> index bcf95d3..e23e0e7 100644
> --- a/sound/core/pcm_lib.c
> +++ b/sound/core/pcm_lib.c
> @@ -67,6 +67,8 @@ void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_ufram
>  	} else {
>  		if (new_hw_ptr == ULONG_MAX) {	/* initialization */
>  			snd_pcm_sframes_t avail = snd_pcm_playback_hw_avail(runtime);
> +			if (avail > runtime->buffer_size)
> +				avail = runtime->buffer_size;
>  			runtime->silence_filled = avail > 0 ? avail : 0;
>  			runtime->silence_start = (runtime->status->hw_ptr +
>  						  runtime->silence_filled) %
>
> But it looks that you do something wrong with hw_ptr or appl_ptr in your
> driver, because this condition would be true only when an large underrun
> occurs immediatelly.

Not underrun but overfill (but this should not occur - the PCM core 
functions check for this). Could you print appl_ptr, hw_ptr and 
buffer_size before you call snd_pcm_elapsed()?

 						Jaroslav

-----
Jaroslav Kysela <perex at perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.