access/alsa.c: mmap capture mode.

Capture using alsa mmap functions.

modules/access/alsa.c

@@ -66,6 +66,10 @@
 static int  DemuxOpen ( vlc_object_t * );
 static void DemuxClose( vlc_object_t * );
 
+#define MMAP_TEXT N_( "Memory Mapped I/O" )
+#define MMAP_LONGTEXT N_( \
+    "Capture audio samples using mmap I/O API." )
+
 #define STEREO_TEXT N_( "Stereo" )
 #define STEREO_LONGTEXT N_( \
     "Capture the audio stream in stereo." )
@@ -102,6 +106,8 @@ vlc_module_begin()
     set_capability( "access_demux", 10 )
     set_callbacks( DemuxOpen, DemuxClose )
 
+    add_bool( CFG_PREFIX "mmap", false, MMAP_TEXT, MMAP_LONGTEXT,
+              false )
     add_bool( CFG_PREFIX "stereo", true, STEREO_TEXT, STEREO_LONGTEXT,
                 true )
     add_string( CFG_PREFIX "format", "s16l", FORMAT_TEXT,
@@ -131,6 +137,7 @@ struct demux_sys_t
     /* Audio */
     int i_cache;
     unsigned int i_sample_rate;
+    bool b_mmap;    /* mmap'ed I/O */
     bool b_stereo;
     vlc_fourcc_t i_format;
     size_t i_max_frame_size;
@@ -278,6 +285,7 @@ static int DemuxOpen( vlc_object_t *p_this )
     free( psz_format );
 
     p_sys->i_sample_rate = var_InheritInteger( p_demux, CFG_PREFIX "samplerate" );
+    p_sys->b_mmap = var_InheritBool( p_demux, CFG_PREFIX "mmap" );
     p_sys->b_stereo = var_InheritBool( p_demux, CFG_PREFIX "stereo" );
     p_sys->i_cache = var_InheritInteger( p_demux, CFG_PREFIX "caching" );
     p_sys->p_es = NULL;
@@ -405,8 +413,10 @@ static block_t* GrabAudio( demux_t *p_demux )
     p_sys->p_block = p_block;
 
     /* ALSA */
-    i_read = snd_pcm_readi( p_sys->p_alsa_pcm, p_block->p_buffer,
-                            p_sys->i_alsa_chunk_size );
+    if( p_sys->b_mmap )
+        i_read = snd_pcm_mmap_readi( p_sys->p_alsa_pcm, p_block->p_buffer, p_sys->i_alsa_chunk_size );
+    else
+        i_read = snd_pcm_readi( p_sys->p_alsa_pcm, p_block->p_buffer, p_sys->i_alsa_chunk_size );
     if( i_read == -EAGAIN )
     {
         snd_pcm_wait( p_sys->p_alsa_pcm, 10 ); /* See poll() comment in oss.c */
@@ -567,6 +577,7 @@ static int OpenAudioDevAlsa( demux_t *p_demux, const char *psz_device )
 
     /* Set Interleaved access */
     if( ( i_err = snd_pcm_hw_params_set_access( p_sys->p_alsa_pcm, p_hw_params,
+                    p_sys->b_mmap ? SND_PCM_ACCESS_MMAP_INTERLEAVED :
                                     SND_PCM_ACCESS_RW_INTERLEAVED ) ) < 0 )
     {
         msg_Err( p_demux, "ALSA: cannot set access type (%s)",