/*
 * This file was stolen from ffmpeg and modified for usability here.
 *  The original is
 * 
 * Copyright (c) 2003 Fabrice Bellard
 * Copyright (c) 2003 Michael Niedermayer
 * Copyright (c) 2009 Alex Converse
 *
 * This version is a derivative work of that version.  It is not free
 *  software; it is licensed under the GNU Lesser General Public
 *  License version 2.1, which places nontrivial restrictions on what
 *  may be done with it.  (I'm not terribly happy about that, but for
 *  my purposes accepting LGPL-infected code is a lower price than
 *  reimplementing it all myself.)
 *
 * The LGPL v2.1 as distributed with ffmpeg is in the accompanying file
 *  `LGPL-v2.1'.
 */

#include "get_bits.h"
#include "aacadtsdec.h"
#include "mpeg4audio.h"
#include "aac_ac3_parser.h"

int avpriv_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(!avpriv_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    = avpriv_mpeg4audio_sample_rates[sr];
    hdr->samples        = (rdb + 1) * 1024;
    hdr->bit_rate       = size * 8 * hdr->sample_rate / hdr->samples;

    return size;
}