issue snd_pcm_start() when capturing audio

snd_pcm_start() starts the capture process and ensures that the events
are delivered to the poll handler. Without the call, capture can be started
only when there is simultaneous playback running.
Signed-off-by: NJindrich Makovicka <makovick@gmail.com>
Signed-off-by: Nmalc <av1474@comtv.ru>

audio/alsaaudio.c

@@ -843,11 +843,15 @@ static int alsa_init_out (HWVoiceOut *hw, struct audsettings *as)
     return 0;
 }
 
-static int alsa_voice_ctl (snd_pcm_t *handle, const char *typ, int pause)
+#define VOICE_CTL_PAUSE 0
+#define VOICE_CTL_PREPARE 1
+#define VOICE_CTL_START 2
+
+static int alsa_voice_ctl (snd_pcm_t *handle, const char *typ, int ctl)
 {
     int err;
 
-    if (pause) {
+    if (ctl == VOICE_CTL_PAUSE) {
         err = snd_pcm_drop (handle);
         if (err < 0) {
             alsa_logerr (err, "Could not stop %s\n", typ);
@@ -860,6 +864,13 @@ static int alsa_voice_ctl (snd_pcm_t *handle, const char *typ, int pause)
             alsa_logerr (err, "Could not prepare handle for %s\n", typ);
             return -1;
         }
+        if (ctl == VOICE_CTL_START) {
+            err = snd_pcm_start(handle);
+            if (err < 0) {
+                alsa_logerr (err, "Could not start handle for %s\n", typ);
+                return -1;
+            }
+        }
     }
 
     return 0;
@@ -884,7 +895,7 @@ static int alsa_ctl_out (HWVoiceOut *hw, int cmd, ...)
                 poll_mode = 0;
             }
             hw->poll_mode = poll_mode;
-            return alsa_voice_ctl (alsa->handle, "playback", 0);
+            return alsa_voice_ctl (alsa->handle, "playback", VOICE_CTL_PREPARE);
         }
 
     case VOICE_DISABLE:
@@ -893,7 +904,7 @@ static int alsa_ctl_out (HWVoiceOut *hw, int cmd, ...)
             hw->poll_mode = 0;
             alsa_fini_poll (&alsa->pollhlp);
         }
-        return alsa_voice_ctl (alsa->handle, "playback", 1);
+        return alsa_voice_ctl (alsa->handle, "playback", VOICE_CTL_PAUSE);
     }
 
     return -1;
@@ -1106,7 +1117,7 @@ static int alsa_ctl_in (HWVoiceIn *hw, int cmd, ...)
             }
             hw->poll_mode = poll_mode;
 
-            return alsa_voice_ctl (alsa->handle, "capture", 0);
+            return alsa_voice_ctl (alsa->handle, "capture", VOICE_CTL_START);
         }
 
     case VOICE_DISABLE:
@@ -1115,7 +1126,7 @@ static int alsa_ctl_in (HWVoiceIn *hw, int cmd, ...)
             hw->poll_mode = 0;
             alsa_fini_poll (&alsa->pollhlp);
         }
-        return alsa_voice_ctl (alsa->handle, "capture", 1);
+        return alsa_voice_ctl (alsa->handle, "capture", VOICE_CTL_PAUSE);
     }
 
     return -1;