Subroutine to copy an AAC Program Config Element (PCE)

Originally committed as revision 18817 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpeg4audio.c

 /*
  * MPEG-4 Audio common code
  * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>
+ * Copyright (c) 2009 Alex Converse <alex.converse@gmail.com>
  *
  * This file is part of FFmpeg.
  *
@@ -20,6 +21,7 @@
  */
 
 #include "get_bits.h"
+#include "put_bits.h"
 #include "mpeg4audio.h"
 
 const int ff_mpeg4audio_sample_rates[16] = {
@@ -84,3 +86,43 @@ int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_si
     }
     return specific_config_bitindex;
 }
+
+static av_always_inline unsigned int copy_bits(PutBitContext *pb,
+                                               GetBitContext *gb,
+                                               int bits)
+{
+    unsigned int el = get_bits(gb, bits);
+    put_bits(pb, bits, el);
+    return el;
+}
+
+int ff_copy_pce_data(PutBitContext *pb, GetBitContext *gb)
+{
+    int five_bit_ch, four_bit_ch, comment_size, bits;
+    int offset = put_bits_count(pb);
+
+    copy_bits(pb, gb, 10);                  //Tag, Object Type, Frequency
+    five_bit_ch  = copy_bits(pb, gb, 4);    //Front
+    five_bit_ch += copy_bits(pb, gb, 4);    //Side
+    five_bit_ch += copy_bits(pb, gb, 4);    //Back
+    four_bit_ch  = copy_bits(pb, gb, 2);    //LFE
+    four_bit_ch += copy_bits(pb, gb, 3);    //Data
+    five_bit_ch += copy_bits(pb, gb, 4);    //Coupling
+    if (copy_bits(pb, gb, 1))               //Mono Mixdown
+        copy_bits(pb, gb, 4);
+    if (copy_bits(pb, gb, 1))               //Stereo Mixdown
+        copy_bits(pb, gb, 4);
+    if (copy_bits(pb, gb, 1))               //Matrix Mixdown
+        copy_bits(pb, gb, 3);
+    for (bits = five_bit_ch*5+four_bit_ch*4; bits > 16; bits -= 16)
+        copy_bits(pb, gb, 16);
+    if (bits)
+        copy_bits(pb, gb, bits);
+    align_put_bits(pb);
+    align_get_bits(gb);
+    comment_size = copy_bits(pb, gb, 8);
+    for (; comment_size > 0; comment_size--)
+        copy_bits(pb, gb, 8);
+
+    return put_bits_count(pb) - offset;
+}

libavcodec/mpeg4audio.h

@@ -23,6 +23,8 @@
 #define AVCODEC_MPEG4AUDIO_H
 
 #include <stdint.h>
+#include "get_bits.h"
+#include "put_bits.h"
 
 typedef struct {
     int object_type;
@@ -90,4 +92,9 @@ enum AudioObjectType {
     AOT_SMR_MAIN,              ///< N                       Symbolic Music Representation Main
 };
 
+#define MAX_PCE_SIZE 304 ///<Maximum size of a PCE including the 3-bit ID_PCE
+                         ///<marker and the comment
+
+int ff_copy_pce_data(PutBitContext *pb, GetBitContext *gb);
+
 #endif /* AVCODEC_MPEG4AUDIO_H */