[patch] dmix skipping first set of samples

[patch] dmix skipping first set of samples

[Mike Gorse]

There was a change in alsa-lib 1.0.16 which looks like it was designed to 
make dmix skip samples in the case of underruns, but it causes the first 
sample to be skipped since dmix->slave_hw_ptr == dmix->slave_appl_ptr. 
The following patch fixes this and fixes a small typo in the comment:

--- src/pcm/pcm_dmix.c.orig	2008-01-18 20:00:10.000000000 -0500
+++ src/pcm/pcm_dmix.c	2008-03-09 18:01:13.000000000 -0400
@@ -311,9 +311,9 @@
  	if (size >= pcm->boundary / 2)
  		size = pcm->boundary - size;

-	/* the slave_app_ptr can be far behing the slave_hw_ptr */
+	/* the slave_app_ptr can be far behind the slave_hw_ptr */
  	/* reduce mixing and errors here - just skip not catched writes */
-	if (dmix->slave_hw_ptr < dmix->slave_appl_ptr)
+	if (dmix->slave_hw_ptr <= dmix->slave_appl_ptr)
  		slave_size = dmix->slave_appl_ptr - dmix->slave_hw_ptr;
  	else
  		slave_size = dmix->slave_appl_ptr + (dmix->slave_boundary - dmix->slave_hw_ptr);

Thanks,
-- Mike Gorse / AIM:linvortex / http://mgorse.freeshell.org --

Re: [patch] dmix skipping first set of samples

[Takashi Iwai]

At Sun, 9 Mar 2008 18:20:47 -0400 (EDT),
Mike Gorse wrote:
> 
> There was a change in alsa-lib 1.0.16 which looks like it was designed to 
> make dmix skip samples in the case of underruns, but it causes the first 
> sample to be skipped since dmix->slave_hw_ptr == dmix->slave_appl_ptr. 
> The following patch fixes this and fixes a small typo in the comment:

A good catch!  Applied to HG tree now.

Thanks.


Takashi

> 
> --- src/pcm/pcm_dmix.c.orig	2008-01-18 20:00:10.000000000 -0500
> +++ src/pcm/pcm_dmix.c	2008-03-09 18:01:13.000000000 -0400
> @@ -311,9 +311,9 @@
>   	if (size >= pcm->boundary / 2)
>   		size = pcm->boundary - size;
> 
> -	/* the slave_app_ptr can be far behing the slave_hw_ptr */
> +	/* the slave_app_ptr can be far behind the slave_hw_ptr */
>   	/* reduce mixing and errors here - just skip not catched writes */
> -	if (dmix->slave_hw_ptr < dmix->slave_appl_ptr)
> +	if (dmix->slave_hw_ptr <= dmix->slave_appl_ptr)
>   		slave_size = dmix->slave_appl_ptr - dmix->slave_hw_ptr;
>   	else
>   		slave_size = dmix->slave_appl_ptr + (dmix->slave_boundary - dmix->slave_hw_ptr);
> 
> Thanks,
> -- Mike Gorse / AIM:linvortex / http://mgorse.freeshell.org --
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