[FFmpeg-devel] [PATCH v3] avcodec/atrac3plus: reorder channels to match the output layout

[James Almer <jamrial@gmail.com>]

The order in which the channels are coded in the bitstream do not always follow
the native, bitmask-based order of channels both signaled by the WAV container
and forced by this same decoder. This is the case with layouts containing an
LFE channel, as it's always coded last.

Fixes ticket #9964.

Signed-off-by: James Almer <jamrial@gmail.com>
---
 libavcodec/atrac3plusdec.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/libavcodec/atrac3plusdec.c b/libavcodec/atrac3plusdec.c
index ee71645a3c..2bc023cb23 100644
--- a/libavcodec/atrac3plusdec.c
+++ b/libavcodec/atrac3plusdec.c
@@ -48,6 +48,17 @@
 #include "atrac.h"
 #include "atrac3plus.h"
 
+static const uint8_t channel_map[8][8] = {
+    { 0, },
+    { 0, 1, },
+    { 0, 1, 2, },
+    { 0, 1, 2, 3, },
+    { 0, },
+    { 0, 1, 2, 4, 5, 3, },
+    { 0, 1, 2, 4, 5, 6, 3, },
+    { 0, 1, 2, 4, 5, 6, 7, 3, },
+};
+
 typedef struct ATRAC3PContext {
     GetBitContext gb;
     AVFloatDSPContext *fdsp;
@@ -65,6 +76,7 @@ typedef struct ATRAC3PContext {
 
     int num_channel_blocks;     ///< number of channel blocks
     uint8_t channel_blocks[5];  ///< channel configuration descriptor
+    const uint8_t *channel_map; ///< channel layout map
 } ATRAC3PContext;
 
 static av_cold int atrac3p_decode_close(AVCodecContext *avctx)
@@ -143,6 +155,8 @@ static av_cold int set_channel_params(ATRAC3PContext *ctx,
         return AVERROR_INVALIDDATA;
     }
 
+    ctx->channel_map = channel_map[channels - 1];
+
     return 0;
 }
 
@@ -378,7 +392,7 @@ static int atrac3p_decode_frame(AVCodecContext *avctx, AVFrame *frame,
                           channels_to_process, avctx);
 
         for (i = 0; i < channels_to_process; i++)
-            memcpy(samples_p[out_ch_index + i], ctx->outp_buf[i],
+            memcpy(samples_p[ctx->channel_map[out_ch_index + i]], ctx->outp_buf[i],
                    ATRAC3P_FRAME_SAMPLES * sizeof(**samples_p));
 
         ch_block++;
-- 
2.38.1

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