[vlc-devel] [PATCH] faad: do not reorder Ambisonics channels

[Adrien Maglo]

Keep the original decoded order to achieve a correct Ambisonics rendering.
---
 modules/codec/faad.c | 49 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 33 insertions(+), 16 deletions(-)

diff --git a/modules/codec/faad.c b/modules/codec/faad.c
index 30b5ac20fe..34733765f2 100644
--- a/modules/codec/faad.c
+++ b/modules/codec/faad.c
@@ -512,24 +512,38 @@ static int DecodeBlock( decoder_t *p_dec, block_t *p_block )
 
         /* Convert frame.channel_position to our own channel values */
         p_dec->fmt_out.audio.i_physical_channels = 0;
-        uint32_t pi_faad_channels_positions[FAAD_CHANNEL_ID_COUNT] = {0};
+
         uint8_t  pi_neworder_table[AOUT_CHAN_MAX];
-        for( size_t i = 0; i < frame.channels; i++ )
+        uint32_t pi_faad_channels_positions[FAAD_CHANNEL_ID_COUNT] = {0};
+
+        switch( p_dec->fmt_out.audio.channel_type )
         {
-            unsigned pos = frame.channel_position[i];
-            if( likely(pos < FAAD_CHANNEL_ID_COUNT) )
+        case AUDIO_CHANNEL_TYPE_BITMAP:
+            for( size_t i = 0; i < frame.channels; i++ )
             {
-                pi_faad_channels_positions[i] = pi_tovlcmapping[pos];
-                p_dec->fmt_out.audio.i_physical_channels |= pi_faad_channels_positions[i];
+                unsigned pos = frame.channel_position[i];
+                if( likely(pos < FAAD_CHANNEL_ID_COUNT) )
+                {
+                    pi_faad_channels_positions[i] = pi_tovlcmapping[pos];
+                    p_dec->fmt_out.audio.i_physical_channels |= pi_faad_channels_positions[i];
+                }
+                else pi_faad_channels_positions[i] = 0;
             }
-            else pi_faad_channels_positions[i] = 0;
-        }
-
-        aout_CheckChannelReorder( pi_faad_channels_positions, NULL,
-                                  p_dec->fmt_out.audio.i_physical_channels, pi_neworder_table );
-
 
-        p_dec->fmt_out.audio.i_channels = popcount(p_dec->fmt_out.audio.i_physical_channels);
+            aout_CheckChannelReorder( pi_faad_channels_positions, NULL,
+                                      p_dec->fmt_out.audio.i_physical_channels, pi_neworder_table );
+
+            p_dec->fmt_out.audio.i_channels = popcount(p_dec->fmt_out.audio.i_physical_channels);
+            break;
+        case AUDIO_CHANNEL_TYPE_AMBISONICS:
+            for( size_t i = 0; i < frame.channels; i++ )
+                pi_neworder_table[i] = i;
+            p_dec->fmt_out.audio.i_channels = frame.channels;
+            break;
+        default:
+            vlc_assert_unreachable();
+            break;
+        }
 
         if( !decoder_UpdateAudioFormat( p_dec ) && p_dec->fmt_out.audio.i_channels > 0 )
             p_out = decoder_NewAudioBuffer( p_dec, frame.samples / p_dec->fmt_out.audio.i_channels );
@@ -541,9 +555,12 @@ static int DecodeBlock( decoder_t *p_dec, block_t *p_block )
                                               frame.samples / frame.channels )
                               - p_out->i_pts;
 
-            /* Don't kill speakers if some weird mapping does not gets 1:1 */
-            if( popcount(p_dec->fmt_out.audio.i_physical_channels) != frame.channels )
-                memset( p_out->p_buffer, 0, p_out->i_buffer );
+            if ( p_dec->fmt_out.audio.channel_type == AUDIO_CHANNEL_TYPE_BITMAP )
+            {
+                /* Don't kill speakers if some weird mapping does not gets 1:1 */
+                if( popcount(p_dec->fmt_out.audio.i_physical_channels) != frame.channels )
+                    memset( p_out->p_buffer, 0, p_out->i_buffer );
+            }
 
             /* FIXME: replace when aout_channel_reorder can take samples from a different buffer */
             DoReordering( (uint32_t *)p_out->p_buffer, samples,
-- 
2.11.0