Takashi Iwai wrote:
> At Sat, 20 May 2006 20:46:34 +0200,
> Gerald Grabner wrote:
>> Takashi Iwai wrote:
>>> At Fri, 19 May 2006 21:17:45 +0000 (UTC),
>>> Gerald Grabner wrote:
>>>> Takashi Iwai <tiwai <at> suse.de> writes:
>>>>> At Mon, 15 May 2006 12:06:47 +0200,
>>>>> I wrote:
>>>>>> At Sat, 13 May 2006 13:06:51 +0200,
>>>>>> Gerald Grabner wrote:
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm experimenting with the ALSA PCM API and was wondering whether
>>>>>>> there is a simple way to exit a record loop by stopping the pcm, but
>>>>>>> without loosing pending frames.
>>>>>>>
>>>>>>> Initially, I was thinking of something like this, where I would call
>>>>>>> snd_pcm_drop(pcm) from some other thread:
>>>>>>>
>>>>>>> while ( true )
>>>>>>> {
>>>>>>> r = snd_pcm_readi (pcm, data, frames);
>>>>>>> fwrite (data, 2, 2*r, file);
>>>>>>> if ( r != frames )
>>>>>>> break;
>>>>>>> }
>>>>>>>
>>>>>>> However, snd_pcm_drain(pcm) doesn't work here; the loop continues.
>>>>>>> snd_pcm_drop(pcm) breaks the loop, but pending frames are lost, and
>>>>>>> r=-EBADFD.
>>>>>>>
>>>>>>> Is there an easy way to stop snd_pcm_readi in a way that I can
>>>>>>> retrieve the residual frames? Do I need to set any parameters for
>>>>>>> that purpose?
>>>>>> If you're using hw or plughw, it's likely a bug in alsa-driver.
>>>>>> Try the patch below.
>>>>> Actually the patch was also wrong. snd_pcm_drain() shouldn't wait for
>>>>> the capture streams. So, the patch becomes pretty simple like below.
>>>>> I'll commit it to HG repo.
>>>>>
>>>>> Takashi
>>>>>
>>>>> diff -r 44d28ed5d3d5 core/pcm_native.c
>>>>> --- a/core/pcm_native.c Wed May 17 11:26:39 2006 +0200
>>>>> +++ b/core/pcm_native.c Wed May 17 17:07:17 2006 +0200
>>>>> <at> <at> -1469,8 +1469,6 <at> <at> static int snd_pcm_drain(
>>>> struct snd_pcm_
>>>>> }
>>>>> }
>>>>> up_read(&snd_pcm_link_rwsem);
>>>>> - if (! num_drecs)
>>>>> - goto _error;
>>>>>
>>>>> snd_pcm_stream_lock_irq(substream);
>>>>> /* resume pause */
>>>> Hi Takashi,
>>>>
>>>> there seems to be some problem with this patch (the short one). After
>>>> recompiling the kernel (and my application), my application doesn't
>>>> exit and I can't kill it anymore. The pcm device is kind of lost. See
>>>> below for the /var/log/messages entry.
>>> Hmm, according the error message below, I suspect it's something
>>> different since the patch isn't so intrusive.
>>>
>>> Could you test again after reverting the patched part?
>> After recompiling the kernel with the original source, the problem
>> disappeared.
>
> OK, could you try the patch below?
>
>
> thanks,
>
> Takashi
>
>
> ------------------------------------------------------------------------
>
> diff -r 18da48cda4cc core/pcm_native.c
> --- a/core/pcm_native.c Mon May 22 12:05:42 2006 +0200
> +++ b/core/pcm_native.c Mon May 22 12:39:22 2006 +0200
> @@ -1381,7 +1381,8 @@ static int snd_pcm_do_drain_init(struct
> if (runtime->status->state == SNDRV_PCM_STATE_RUNNING) {
> int state = snd_pcm_capture_avail(runtime) > 0 ?
> SNDRV_PCM_STATE_DRAINING : SNDRV_PCM_STATE_SETUP;
> - snd_pcm_do_stop(substream, state);
> + substream->ops->trigger(substream,
> + SNDRV_PCM_TRIGGER_STOP);
> snd_pcm_post_stop(substream, state);
> }
> }
With this patch, I don't run into the same problem as with the last
one, i.e. there are no error messages.
However, it still doesn't do what I want - which is most probably my
own fault. In my program, there is one thread like this:
while ( true )
{
r = snd_pcm_readi (pcm, data, frames);
fwrite (data, 2, 2*r, file);
if ( r != frames )
break;
}
My idea was to arrive at the break statement by calling
snd_pcm_drain(pcm) from another thread, but without loosing the
pending frames. If I understood Clemens Ladisch correctly, I will have
to use poll() for that purpose...
Thx,
Gerald
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