Change default alsa device lookup

If ALSA_DEFAULT cannot be opened, loop through all available alsa input devices.
(And if an alsa device was provided in the mrl but couldn't be opened, print the list of available alsa input devices in the debug output after the open error message.)

modules/access/alsa.c

@@ -116,13 +116,12 @@ static int Demux( demux_t * );
 
 static block_t* GrabAudio( demux_t *p_demux );
 
-static int OpenAudioDev( demux_t * );
-static bool ProbeAudioDevAlsa( demux_t *, const char *psz_device );
+static int OpenAudioDev( demux_t *, const char * );
+static bool ProbeAudioDevAlsa( demux_t *, const char * );
+static char *ListAvailableDevices( demux_t *, bool b_probe );
 
 struct demux_sys_t
 {
-    const char *psz_device;  /* Alsa device from MRL */
-
     /* Audio */
     int i_cache;
     unsigned int i_sample_rate;
@@ -139,16 +138,27 @@ struct demux_sys_t
     int64_t i_next_demux_date; /* Used to handle alsa:// as input-slave properly */
 };
 
-static int FindMainDevice( demux_t *p_demux )
+static int FindMainDevice( demux_t *p_demux, const char *psz_device )
 {
-    /* TODO: if using default device, loop through all alsa devices until
-     * one works. */
-    msg_Dbg( p_demux, "opening device '%s'", p_demux->p_sys->psz_device );
-    if( ProbeAudioDevAlsa( p_demux, p_demux->p_sys->psz_device ) )
+    if( psz_device )
+    {
+        msg_Dbg( p_demux, "opening device '%s'", psz_device );
+        if( ProbeAudioDevAlsa( p_demux, psz_device ) )
+        {
+            msg_Dbg( p_demux, "'%s' is an audio device", psz_device );
+            OpenAudioDev( p_demux, psz_device );
+        }
+    }
+    else if( ProbeAudioDevAlsa( p_demux, ALSA_DEFAULT ) )
     {
-        msg_Dbg( p_demux, "'%s' is an audio device",
-                 p_demux->p_sys->psz_device );
-        OpenAudioDev( p_demux );
+        msg_Dbg( p_demux, "'%s' is an audio device", ALSA_DEFAULT );
+        OpenAudioDev( p_demux, ALSA_DEFAULT );
+    }
+    else if( ( psz_device = ListAvailableDevices( p_demux, true ) ) )
+    {
+        msg_Dbg( p_demux, "'%s' is an audio device", psz_device );
+        OpenAudioDev( p_demux, psz_device );
+        free( (char *)psz_device );
     }
 
     if( p_demux->p_sys->p_alsa_pcm == NULL )
@@ -156,7 +166,7 @@ static int FindMainDevice( demux_t *p_demux )
     return VLC_SUCCESS;
 }
 
-static void ListAvailableDevices( demux_t *p_demux )
+static char *ListAvailableDevices( demux_t *p_demux, bool b_probe )
 {
     snd_ctl_card_info_t *p_info = NULL;
     snd_ctl_card_info_alloca( &p_info );
@@ -164,7 +174,8 @@ static void ListAvailableDevices( demux_t *p_demux )
     snd_pcm_info_t *p_pcminfo = NULL;
     snd_pcm_info_alloca( &p_pcminfo );
 
-    msg_Dbg( p_demux, "Available alsa capture devices:" );
+    if( !b_probe )
+        msg_Dbg( p_demux, "Available alsa capture devices:" );
     int i_card = -1;
     while( !snd_card_next( &i_card ) && i_card >= 0 )
     {
@@ -175,9 +186,10 @@ static void ListAvailableDevices( demux_t *p_demux )
         if( snd_ctl_open( &p_ctl, psz_devname, 0 ) < 0 ) continue;
 
         snd_ctl_card_info( p_ctl, p_info );
-        msg_Dbg( p_demux, "  %s (%s)",
-                 snd_ctl_card_info_get_id( p_info ),
-                 snd_ctl_card_info_get_name( p_info ) );
+        if( !b_probe )
+            msg_Dbg( p_demux, "  %s (%s)",
+                     snd_ctl_card_info_get_id( p_info ),
+                     snd_ctl_card_info_get_name( p_info ) );
 
         int i_dev = -1;
         while( !snd_ctl_pcm_next_device( p_ctl, &i_dev ) && i_dev >= 0 )
@@ -187,13 +199,29 @@ static void ListAvailableDevices( demux_t *p_demux )
             snd_pcm_info_set_stream( p_pcminfo, SND_PCM_STREAM_CAPTURE );
             if( snd_ctl_pcm_info( p_ctl, p_pcminfo ) < 0 ) continue;
 
-            msg_Dbg( p_demux, "    hw:%d,%d : %s (%s)", i_card, i_dev,
-                     snd_pcm_info_get_id( p_pcminfo ),
-                     snd_pcm_info_get_name( p_pcminfo ) );
+            if( !b_probe )
+                msg_Dbg( p_demux, "    hw:%d,%d : %s (%s)", i_card, i_dev,
+                         snd_pcm_info_get_id( p_pcminfo ),
+                         snd_pcm_info_get_name( p_pcminfo ) );
+            else
+            {
+                char *psz_device;
+                if( asprintf( &psz_device, "hw:%d,%d", i_card, i_dev ) > 0 )
+                {
+                    if( ProbeAudioDevAlsa( p_demux, psz_device ) )
+                    {
+                        snd_ctl_close( p_ctl );
+                        return psz_device;
+                    }
+                    else
+                        free( psz_device );
+                }
+            }
         }
 
         snd_ctl_close( p_ctl );
     }
+    return NULL;
 }
 
 /*****************************************************************************
@@ -228,16 +256,16 @@ static int DemuxOpen( vlc_object_t *p_this )
     p_sys->p_block = NULL;
     p_sys->i_next_demux_date = -1;
 
+    const char *psz_device = NULL;
     if( p_demux->psz_path && *p_demux->psz_path )
-        p_sys->psz_device = p_demux->psz_path;
+        psz_device = p_demux->psz_path;
     else
-    {
-        p_sys->psz_device = ALSA_DEFAULT;
-        ListAvailableDevices( p_demux );
-    }
+        ListAvailableDevices( p_demux, false );
 
-    if( FindMainDevice( p_demux ) != VLC_SUCCESS )
+    if( FindMainDevice( p_demux, psz_device ) != VLC_SUCCESS )
     {
+        if( p_demux->psz_path && *p_demux->psz_path )
+            ListAvailableDevices( p_demux, false );
         DemuxClose( p_this );
         return VLC_EGENERIC;
     }
@@ -443,10 +471,9 @@ static block_t* GrabAudio( demux_t *p_demux )
 /*****************************************************************************
  * OpenAudioDev: open and set up the audio device and probe for capabilities
  *****************************************************************************/
-static int OpenAudioDevAlsa( demux_t *p_demux )
+static int OpenAudioDevAlsa( demux_t *p_demux, const char *psz_device )
 {
     demux_sys_t *p_sys = p_demux->p_sys;
-    const char *psz_device = p_sys->psz_device;
     p_sys->p_alsa_pcm = NULL;
     snd_pcm_hw_params_t *p_hw_params = NULL;
     snd_pcm_uframes_t buffer_size;
@@ -612,14 +639,14 @@ static int OpenAudioDevAlsa( demux_t *p_demux )
 
 }
 
-static int OpenAudioDev( demux_t *p_demux )
+static int OpenAudioDev( demux_t *p_demux, const char *psz_device )
 {
     demux_sys_t *p_sys = p_demux->p_sys;
-    if( OpenAudioDevAlsa( p_demux ) != VLC_SUCCESS )
+    if( OpenAudioDevAlsa( p_demux, psz_device ) != VLC_SUCCESS )
         return VLC_EGENERIC;
 
     msg_Dbg( p_demux, "opened adev=`%s' %s %dHz",
-             p_sys->psz_device, p_sys->b_stereo ? "stereo" : "mono",
+             psz_device, p_sys->b_stereo ? "stereo" : "mono",
              p_sys->i_sample_rate );
 
     es_format_t fmt;