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libavcodec/aac_parser.c

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00001 /*
00002  * Audio and Video frame extraction
00003  * Copyright (c) 2003 Fabrice Bellard
00004  * Copyright (c) 2003 Michael Niedermayer
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "parser.h"
00024 #include "aac_ac3_parser.h"
00025 #include "aac_parser.h"
00026 #include "bitstream.h"
00027 #include "mpeg4audio.h"
00028 
00029 #define AAC_HEADER_SIZE 7
00030 
00031 int ff_aac_parse_header(GetBitContext *gbc, AACADTSHeaderInfo *hdr)
00032 {
00033     int size, rdb, ch, sr;
00034     int aot, crc_abs;
00035 
00036     if(get_bits(gbc, 12) != 0xfff)
00037         return AAC_AC3_PARSE_ERROR_SYNC;
00038 
00039     skip_bits1(gbc);             /* id */
00040     skip_bits(gbc, 2);           /* layer */
00041     crc_abs = get_bits1(gbc);    /* protection_absent */
00042     aot     = get_bits(gbc, 2);  /* profile_objecttype */
00043     sr      = get_bits(gbc, 4);  /* sample_frequency_index */
00044     if(!ff_mpeg4audio_sample_rates[sr])
00045         return AAC_AC3_PARSE_ERROR_SAMPLE_RATE;
00046     skip_bits1(gbc);             /* private_bit */
00047     ch      = get_bits(gbc, 3);  /* channel_configuration */
00048 
00049     if(!ff_mpeg4audio_channels[ch])
00050         return AAC_AC3_PARSE_ERROR_CHANNEL_CFG;
00051 
00052     skip_bits1(gbc);             /* original/copy */
00053     skip_bits1(gbc);             /* home */
00054 
00055     /* adts_variable_header */
00056     skip_bits1(gbc);             /* copyright_identification_bit */
00057     skip_bits1(gbc);             /* copyright_identification_start */
00058     size    = get_bits(gbc, 13); /* aac_frame_length */
00059     if(size < AAC_HEADER_SIZE)
00060         return AAC_AC3_PARSE_ERROR_FRAME_SIZE;
00061 
00062     skip_bits(gbc, 11);          /* adts_buffer_fullness */
00063     rdb = get_bits(gbc, 2);      /* number_of_raw_data_blocks_in_frame */
00064 
00065     hdr->object_type    = aot + 1;
00066     hdr->chan_config    = ch;
00067     hdr->crc_absent     = crc_abs;
00068     hdr->num_aac_frames = rdb + 1;
00069     hdr->sampling_index = sr;
00070     hdr->sample_rate    = ff_mpeg4audio_sample_rates[sr];
00071     hdr->samples        = (rdb + 1) * 1024;
00072     hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;
00073 
00074     return size;
00075 }
00076 
00077 static int aac_sync(uint64_t state, AACAC3ParseContext *hdr_info,
00078         int *need_next_header, int *new_frame_start)
00079 {
00080     GetBitContext bits;
00081     AACADTSHeaderInfo hdr;
00082     int size;
00083     union {
00084         uint64_t u64;
00085         uint8_t  u8[8];
00086     } tmp;
00087 
00088     tmp.u64 = be2me_64(state);
00089     init_get_bits(&bits, tmp.u8+8-AAC_HEADER_SIZE, AAC_HEADER_SIZE * 8);
00090 
00091     if ((size = ff_aac_parse_header(&bits, &hdr)) < 0)
00092         return 0;
00093     *need_next_header = 0;
00094     *new_frame_start  = 1;
00095     hdr_info->sample_rate = hdr.sample_rate;
00096     hdr_info->channels    = ff_mpeg4audio_channels[hdr.chan_config];
00097     hdr_info->samples     = hdr.samples;
00098     hdr_info->bit_rate    = hdr.bit_rate;
00099     return size;
00100 }
00101 
00102 static av_cold int aac_parse_init(AVCodecParserContext *s1)
00103 {
00104     AACAC3ParseContext *s = s1->priv_data;
00105     s->header_size = AAC_HEADER_SIZE;
00106     s->sync = aac_sync;
00107     return 0;
00108 }
00109 
00110 
00111 AVCodecParser aac_parser = {
00112     { CODEC_ID_AAC },
00113     sizeof(AACAC3ParseContext),
00114     aac_parse_init,
00115     ff_aac_ac3_parse,
00116     ff_parse_close,
00117 };

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