mpeg4audio common code

Originally committed as revision 12662 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 83 insertions, 0 deletions

diff --git a/libavcodec/mpeg4audio.c b/libavcodec/mpeg4audio.c
new file mode 100644
index 0000000000..ce5c723411
--- /dev/null
+++ b/libavcodec/mpeg4audio.c
@@ -0,0 +1,83 @@
+/*
+ * MPEG-4 Audio common code
+ * Copyright (c) 2008 Baptiste Coudurier <baptiste.coudurier@free.fr>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "bitstream.h"
+#include "mpeg4audio.h"
+
+const int ff_mpeg4audio_sample_rates[16] = {
+    96000, 88200, 64000, 48000, 44100, 32000,
+    24000, 22050, 16000, 12000, 11025, 8000, 7350
+};
+
+const uint8_t ff_mpeg4audio_channels[8] = {
+    0, 1, 2, 3, 4, 5, 6, 8
+};
+
+static inline int get_object_type(GetBitContext *gb)
+{
+    int object_type = get_bits(gb, 5);
+    if (object_type == 31)
+        object_type = 32 + get_bits(gb, 6);
+    return object_type;
+}
+
+static inline int get_sample_rate(GetBitContext *gb, int *index)
+{
+    *index = get_bits(gb, 4);
+    return *index == 0x0f ? get_bits(gb, 24) :
+        ff_mpeg4audio_sample_rates[*index];
+}
+
+int ff_mpeg4audio_get_config(MPEG4AudioConfig *c, const uint8_t *buf, int buf_size)
+{
+    GetBitContext gb;
+    int specific_config_bitindex;
+
+    init_get_bits(&gb, buf, buf_size*8);
+    c->object_type = get_object_type(&gb);
+    c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
+    c->chan_config = get_bits(&gb, 4);
+    c->sbr = -1;
+    if (c->object_type == 5) {
+        c->ext_object_type = c->object_type;
+        c->sbr = 1;
+        c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
+        c->object_type = get_object_type(&gb);
+    } else
+        c->ext_object_type = 0;
+
+    specific_config_bitindex = get_bits_count(&gb);
+
+    if (c->ext_object_type != 5) {
+        int bits_left = buf_size*8 - specific_config_bitindex;
+        for (; bits_left > 15; bits_left--) {
+            if (show_bits(&gb, 11) == 0x2b7) { // sync extension
+                get_bits(&gb, 11);
+                c->ext_object_type = get_object_type(&gb);
+                if (c->ext_object_type == 5 && (c->sbr = get_bits1(&gb)) == 1)
+                    c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
+                break;
+            } else
+                get_bits1(&gb); // skip 1 bit
+        }
+    }
+    return specific_config_bitindex;
+}