Add support for MPEG-4 ALS to the MP4 demuxer and FFmpeg wrapper.

MPEG-4 ALS is a pure losses audio codec from MPEG. Like other MPEG-4
Audio variants it's muxed into the MP4 container with Object Type
Indication 0x40 followed by its Audio Object Type (36).

Sample:
http://streams.videolan.org/Mpeg_Conformance/ftp.iis.fhg.de/mpeg4audio-conformance/compressedMp4/als_00_2ch48k16b.mp4Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

include/vlc_fourcc.h

@@ -194,6 +194,7 @@
 /* Audio codec */
 #define VLC_CODEC_MPGA      VLC_FOURCC('m','p','g','a')
 #define VLC_CODEC_MP4A      VLC_FOURCC('m','p','4','a')
+#define VLC_CODEC_ALS       VLC_FOURCC('a','l','s',' ')
 #define VLC_CODEC_A52       VLC_FOURCC('a','5','2',' ')
 #define VLC_CODEC_EAC3      VLC_FOURCC('e','a','c','3')
 #define VLC_CODEC_DTS       VLC_FOURCC('d','t','s',' ')

modules/codec/avcodec/fourcc.c

@@ -296,6 +296,7 @@ static const struct
     { VLC_CODEC_MPGA, CODEC_ID_MP3, AUDIO_ES },
 
     { VLC_CODEC_MP4A, CODEC_ID_AAC, AUDIO_ES },
+    { VLC_CODEC_ALS, CODEC_ID_MP4ALS, AUDIO_ES },
 
     { VLC_CODEC_INTERPLAY_DPCM, CODEC_ID_INTERPLAY_DPCM, AUDIO_ES },
 

modules/demux/mp4/mp4.c

@@ -1727,6 +1727,12 @@ static int TrackCreateES( demux_t *p_demux, mp4_track_t *p_track,
                 break;
             case( 0x40):
                 p_track->fmt.i_codec = VLC_FOURCC( 'm','p','4','a' );
+                if( p_decconfig->i_decoder_specific_info_len >= 2 &&
+                     p_decconfig->p_decoder_specific_info[0]       == 0xF8 &&
+                    (p_decconfig->p_decoder_specific_info[1]&0xE0) == 0x80 )
+                {
+                    p_track->fmt.i_codec = VLC_CODEC_ALS;
+                }
                 break;
             case( 0x60):
             case( 0x61):

src/misc/fourcc.c

@@ -875,6 +875,10 @@ static const entry_t p_list_audio[] = {
         A("mp4a"),
         A("aac "),
 
+    /* ALS audio */
+    B(VLC_CODEC_ALS, "MPEG-4 Audio Lossless (ALS)"),
+        A("als "),
+
     /* 4X Technologies */
     B(VLC_CODEC_ADPCM_4XM, "4X Technologies Audio"),
         A("4xma"),