Split the ADTS header decoder off of the ADTS parser.

The AAC decoder and ADTS-to-ASC BSF both require the header decoder
but not full parsing capabilities.

Originally committed as revision 24217 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 70 insertions, 0 deletions

diff --git a/libavcodec/aacadtsdec.c b/libavcodec/aacadtsdec.c
new file mode 100644
index 0000000000..fd86d288a6
--- /dev/null
+++ b/libavcodec/aacadtsdec.c
@@ -0,0 +1,70 @@
+/*
+ * Audio and Video frame extraction
+ * Copyright (c) 2003 Fabrice Bellard
+ * Copyright (c) 2003 Michael Niedermayer
+ * Copyright (c) 2009 Alex Converse
+ *
+ * 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 "aac_ac3_parser.h"
+#include "aacadtsdec.h"
+#include "get_bits.h"
+#include "mpeg4audio.h"
+
+int ff_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
+{
+    int size, rdb, ch, sr;
+    int aot, crc_abs;
+
+    if(get_bits(gbc, 12) != 0xfff)
+        return AAC_AC3_PARSE_ERROR_SYNC;
+
+    skip_bits1(gbc);             /* id */
+    skip_bits(gbc, 2);           /* layer */
+    crc_abs = get_bits1(gbc);    /* protection_absent */
+    aot     = get_bits(gbc, 2);  /* profile_objecttype */
+    sr      = get_bits(gbc, 4);  /* sample_frequency_index */
+    if(!ff_mpeg4audio_sample_rates[sr])
+        return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
+    skip_bits1(gbc);             /* private_bit */
+    ch      = get_bits(gbc, 3);  /* channel_configuration */
+
+    skip_bits1(gbc);             /* original/copy */
+    skip_bits1(gbc);             /* home */
+
+    /* adts_variable_header */
+    skip_bits1(gbc);             /* copyright_identification_bit */
+    skip_bits1(gbc);             /* copyright_identification_start */
+    size    = get_bits(gbc, 13); /* aac_frame_length */
+    if(size < AAC_ADTS_HEADER_SIZE)
+        return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
+
+    skip_bits(gbc, 11);          /* adts_buffer_fullness */
+    rdb = get_bits(gbc, 2);      /* number_of_raw_data_blocks_in_frame */
+
+    hdr->object_type    = aot + 1;
+    hdr->chan_config    = ch;
+    hdr->crc_absent     = crc_abs;
+    hdr->num_aac_frames = rdb + 1;
+    hdr->sampling_index = sr;
+    hdr->sample_rate    = ff_mpeg4audio_sample_rates[sr];
+    hdr->samples        = (rdb + 1) * 1024;
+    hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;
+
+    return size;
+}