On 24 May 2017 at 20:18, Cheng Sun chengsun9@gmail.com wrote:
Hi all,
The following commit (released in v1.1.3) introduced an issue where dmix reports its state differently when snd_pcm_state is queried, compared to snd_pcm_status.
38a2d2eda880fda9ed5a4a219db498d9c0856d71(I suspect faf53c197cabeb1eb0fd1f66cd001d1469ebac09 affects dshare similarly, but this is not tested)
The sample program attached at the bottom of this email demonstrates this behaviour by printing the following on underrun:
try 1: status_state=3, state=4 try 2: status_state=3, state=4 ALSA lib pcm.c:8306:(snd_pcm_recover) underrun occurred
Cheers, Cheng
Just realised that my original sample program had a slight flaw (snd_pcm_status only called once). Here's the corrected version, which still exhibits the erroneous behaviour.
(Also to clarify, this problem is still present in v1.1.4 and master.)
Cheers, Cheng
---
#include <assert.h> #include <alsa/asoundlib.h> #include <stdint.h> #define FRAMES 100 int32_t buffer[FRAMES][2]; int main(int argc, char *argv[]) { const char *pcmname = argc == 2 ? argv[1] : "default"; snd_pcm_t *pcm; assert( snd_pcm_open(&pcm, pcmname, SND_PCM_STREAM_PLAYBACK, 0) == 0 ); assert( snd_pcm_set_params(pcm, SND_PCM_FORMAT_S32_LE, SND_PCM_ACCESS_RW_INTERLEAVED, 2, 48000, 1, 250) == 0 ); for (;;) { snd_pcm_sframes_t written = snd_pcm_writei(pcm, buffer, FRAMES); if (written <= 0) { snd_pcm_status_t *status; snd_pcm_status_alloca(&status);
int status_state, state;
assert( snd_pcm_status(pcm, status) == 0 ); status_state = snd_pcm_status_get_state(status); state = snd_pcm_state(pcm); printf("try 1: status_state=%d, state=%d\n", status_state, state);
assert( snd_pcm_status(pcm, status) == 0 ); status_state = snd_pcm_status_get_state(status); state = snd_pcm_state(pcm); printf("try 2: status_state=%d, state=%d\n", status_state, state);
assert( snd_pcm_recover(pcm,written,0) == 0 ); } } }