Hi Jaroslav,
Thank you for your suggestion. But unfortunately the problem persists.
Giuliano
-----Messaggio originale----- Da: Jaroslav Kysela perex@perex.cz Inviato: lunedì 25 marzo 2019 16:15 A: Giuliano Zannetti - ART S.p.A. giuliano.zannetti@artgroup-spa.com; alsa-devel@alsa-project.org Cc: Takashi Iwai tiwai@suse.de Oggetto: Re: [alsa-devel] snd_pcm_writei 0 frames
Dne 25. 03. 19 v 15:16 Giuliano Zannetti - ART S.p.A. napsal(a):
Hi,
I've the following configuration in my asound.conf:
|-----| - - > |-----| - - > |-----| - - > |-----| - - > |-----| - - > |-----| |----------| |plug | | | - - > | | - - > | | - - > | | - - > | (output) | |-----| - - > | | - - > | | - - > | | - - > | | - - > | hw | | | - - > | | - - > | | - - > | | - - > | | | | | | |route| - - > |dmix | - - > | | | | | | | | - - > | | - - > | | | | | | | | - - > | | - - > | | | | | | |-----| - - > |-----| - - > |----------| |route| |multi| | | - - > | | | | - - > | | - - > |----| - - > |----| - - > |----------| | | - - > | | - - > | | - - > | | - - > |(loopback)| |-----| - - > | | - - > |plug| - - > |dmix| - - > | hw | |-----| - - > |----| - - > |----| - - > |----------|
As you can see I'm using a loopback interface. I open the pcm plug in the block mode to write.
writtenFrames = snd_pcm_writei(handle, bufferToWrite, bufferToWriteSize);
Using the configuration above I have several "writes" with 0 written frames. It seems like the snd_pcm_writei does not hold until data will be written.
In general, 0 written frames sounds weird to me, because snd_pcm_writei should block itself if no space is available in the circular buffer right?
So, my questions are two:
- Writing 0 frames is an expected behaviour (regardless of my configuration in the asound.conf)? In what scenarios can I have that?
- How my configuration could trigger this behaviour?
I guess that snd_pcm_multi_may_wait_for_avail_min() implementation is the culprit. It should take in account all slaves - not only the master one.
Could you test this modification?
diff --git a/src/pcm/pcm_multi.c b/src/pcm/pcm_multi.c index 28440378..0afd31bf 100644 --- a/src/pcm/pcm_multi.c +++ b/src/pcm/pcm_multi.c @@ -775,11 +775,15 @@ static int snd_pcm_multi_mmap(snd_pcm_t *pcm) return 0; }
-static int snd_pcm_multi_may_wait_for_avail_min(snd_pcm_t *pcm, snd_pcm_uframes_t avail ATTRIBUTE_UNUSED) +static int snd_pcm_multi_may_wait_for_avail_min(snd_pcm_t *pcm, +snd_pcm_uframes_t avail) { snd_pcm_multi_t *multi = pcm->private_data; - snd_pcm_t *slave = multi->slaves[multi->master_slave].pcm; - return snd_pcm_may_wait_for_avail_min(slave, snd_pcm_mmap_avail(slave)); + unsigned int i; + for (i = 0; i < multi->slaves_count; ++i) { + if (snd_pcm_may_wait_for_avail_min(multi->slaves[i].pcm, avail)) + return 1; + } + return 0; }
static snd_pcm_chmap_query_t **snd_pcm_multi_query_chmaps(snd_pcm_t *pcm)
Jaroslav
-- Jaroslav Kysela perex@perex.cz Linux Sound Maintainer; ALSA Project; Red Hat, Inc.