AVI: support WAVEFORMATEXTENSIBLE for audio

This is notably used by files produced by FFmpeg
Closes #4742

modules/demux/avi/avi.c

@@ -401,8 +401,16 @@ static int Open( vlc_object_t * p_this )
         {
             case( AVIFOURCC_auds ):
                 tk->i_cat   = AUDIO_ES;
-                tk->i_codec = AVI_FourccGetCodec( AUDIO_ES,
-                                                  p_auds->p_wf->wFormatTag );
+                if( p_auds->p_wf->wFormatTag == WAVE_FORMAT_EXTENSIBLE &&
+                    p_auds->p_wf->cbSize >= sizeof(WAVEFORMATEXTENSIBLE) - sizeof(WAVEFORMATEX) )
+                {
+                    WAVEFORMATEXTENSIBLE *p_wfe = (WAVEFORMATEXTENSIBLE *)p_auds->p_wf;
+                    tk->i_codec = AVI_FourccGetCodec( AUDIO_ES,
+                                                      p_wfe->SubFormat.Data1 );
+                }
+                else
+                    tk->i_codec = AVI_FourccGetCodec( AUDIO_ES,
+                                                      p_auds->p_wf->wFormatTag );
 
                 tk->i_blocksize = p_auds->p_wf->nBlockAlign;
                 if( tk->i_blocksize == 0 )

modules/demux/avi/libavi.c

@@ -342,10 +342,12 @@ static int AVI_ChunkRead_strf( stream_t *s, avi_chunk_t *p_chk )
             AVI_READ4BYTES( p_chk->strf.auds.p_wf->nAvgBytesPerSec );
             AVI_READ2BYTES( p_chk->strf.auds.p_wf->nBlockAlign );
             AVI_READ2BYTES( p_chk->strf.auds.p_wf->wBitsPerSample );
+
             if( p_chk->strf.auds.p_wf->wFormatTag != WAVE_FORMAT_PCM
                  && p_chk->common.i_chunk_size > sizeof( WAVEFORMATEX ) )
             {
                 AVI_READ2BYTES( p_chk->strf.auds.p_wf->cbSize );
+
                 /* prevent segfault */
                 if( p_chk->strf.auds.p_wf->cbSize >
                         p_chk->common.i_chunk_size - sizeof( WAVEFORMATEX ) )
@@ -353,11 +355,10 @@ static int AVI_ChunkRead_strf( stream_t *s, avi_chunk_t *p_chk )
                     p_chk->strf.auds.p_wf->cbSize =
                         p_chk->common.i_chunk_size - sizeof( WAVEFORMATEX );
                 }
+
                 if( p_chk->strf.auds.p_wf->wFormatTag == WAVE_FORMAT_EXTENSIBLE )
                 {
-                    /* Found an extensible header atm almost nothing uses that. */
-                    msg_Warn( (vlc_object_t*)s, "WAVE_FORMAT_EXTENSIBLE or "
-                              "vorbis audio dectected: not supported" );
+                    msg_Dbg( s, "Extended header found" );
                 }
             }
             else