mpeg4audio.c

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/*
 * 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.
 *
 * 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 "get_bits.h"
#include "mpeg4audio.h"
 
/**
 * Parse MPEG-4 audio configuration for ALS object type.
 * @param[in] gb       bit reader context
 * @param[in] c        MPEG4AudioConfig structure to fill
 * @return on success 0 is returned, otherwise a value < 0
 */
static int parse_config_ALS(GetBitContext *gb, MPEG4AudioConfig *c, void *logctx)
{
    if (get_bits_left(gb) < 112)
        return AVERROR_INVALIDDATA;
 
    if (get_bits_long(gb, 32) != MKBETAG('A','L','S','\0'))
        return AVERROR_INVALIDDATA;
 
    // override AudioSpecificConfig channel configuration and sample rate
    // which are buggy in old ALS conformance files
    c->sample_rate = get_bits_long(gb, 32);
 
    if (c->sample_rate <= 0) {
        av_log(logctx, AV_LOG_ERROR, "Invalid sample rate %d\n", c->sample_rate);
        return AVERROR_INVALIDDATA;
    }
 
    // skip number of samples
    skip_bits_long(gb, 32);
 
    // read number of channels
    c->chan_config = 0;
    c->channels    = get_bits(gb, 16) + 1;
 
    return 0;
}
 
const uint8_t ff_mpeg4audio_channels[15] = {
    0,
    1, // mono (1/0)
    2, // stereo (2/0)
    3, // 3/0
    4, // 3/1
    5, // 3/2
    6, // 3/2.1
    8, // 5/2.1
    0,
    0,
    0,
    7, // 3/3.1
    8, // 3/2/2.1
    24, // 3/3/3 - 5/2/3 - 3/0/0.2
    8, // 3/2.1 - 2/0
};
 
static inline int get_object_type(GetBitContext *gb)
{
    int object_type = get_bits(gb, 5);
    if (object_type == AOT_ESCAPE)
        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_gb(MPEG4AudioConfig *c, GetBitContext *gb,
                                int sync_extension, void *logctx)
{
    int specific_config_bitindex, ret;
    int start_bit_index = get_bits_count(gb);
    c->object_type = get_object_type(gb);
    c->sample_rate = get_sample_rate(gb, &c->sampling_index);
    c->chan_config = get_bits(gb, 4);
    if (c->chan_config < FF_ARRAY_ELEMS(ff_mpeg4audio_channels))
        c->channels = ff_mpeg4audio_channels[c->chan_config];
    else {
        av_log(logctx, AV_LOG_ERROR, "Invalid chan_config %d\n", c->chan_config);
        return AVERROR_INVALIDDATA;
    }
    c->sbr = -1;
    c->ps  = -1;
    if (c->object_type == AOT_SBR || (c->object_type == AOT_PS &&
        // check for W6132 Annex YYYY draft MP3onMP4
        !(show_bits(gb, 3) & 0x03 && !(show_bits(gb, 9) & 0x3F)))) {
        if (c->object_type == AOT_PS)
            c->ps = 1;
        c->ext_object_type = AOT_SBR;
        c->sbr = 1;
        c->ext_sample_rate = get_sample_rate(gb, &c->ext_sampling_index);
        c->object_type = get_object_type(gb);
        if (c->object_type == AOT_ER_BSAC)
            c->ext_chan_config = get_bits(gb, 4);
    } else {
        c->ext_object_type = AOT_NULL;
        c->ext_sample_rate = 0;
    }
    specific_config_bitindex = get_bits_count(gb);
 
    if (c->object_type == AOT_ALS) {
        skip_bits(gb, 5);
        if (show_bits(gb, 24) != MKBETAG('\0','A','L','S'))
            skip_bits(gb, 24);
 
        specific_config_bitindex = get_bits_count(gb);
 
        ret = parse_config_ALS(gb, c, logctx);
        if (ret < 0)
            return ret;
    }
    switch (c->object_type) {
    case AOT_AAC_MAIN:
    case AOT_AAC_LC:
    case AOT_AAC_SSR:
    case AOT_AAC_LTP:
    case AOT_ER_AAC_LC:
        c->frame_length_short = get_bits1(gb);
        c->frame_length = c->frame_length_short ? 960 : 1024;
        break;
    case AOT_ER_AAC_LD:
    case AOT_ER_AAC_ELD:
        c->frame_length_short = get_bits1(gb);
        c->frame_length = c->frame_length_short ? 480 : 512;
        break;
    case AOT_USAC: {
        int core_sbr_frame_len_idx, sbr_ratio;
        int ratio_mult, ratio_dec, frame_length;
        if (get_bits(gb, 5) == 0x1f) /* usacSamplingFrequencyIndex */ {
            skip_bits(gb, 24); /* usacSamplingFrequency */
        }
        core_sbr_frame_len_idx = get_bits(gb, 3);
        c->frame_length_short = core_sbr_frame_len_idx == 0 ||
                                core_sbr_frame_len_idx == 2;
        sbr_ratio = core_sbr_frame_len_idx == 2 ? 2 :
                    core_sbr_frame_len_idx == 3 ? 3 :
                    core_sbr_frame_len_idx == 4 ? 1 :
                    0;
 
        if (sbr_ratio == 2) {
            ratio_mult = 8;
            ratio_dec = 3;
        } else if (sbr_ratio == 3) {
            ratio_mult = 2;
            ratio_dec = 1;
        } else if (sbr_ratio == 4) {
            ratio_mult = 4;
            ratio_dec = 1;
        } else {
            ratio_mult = 1;
            ratio_dec = 1;
        }
 
        frame_length = c->frame_length_short ? 768 : 1024;
        c->frame_length = (frame_length * ratio_mult) / ratio_dec;
        break;
    }
    }
 
    if (c->ext_object_type != AOT_SBR && sync_extension) {
        while (get_bits_left(gb) > 15) {
            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 == AOT_SBR && (c->sbr = get_bits1(gb)) == 1) {
                    c->ext_sample_rate = get_sample_rate(gb, &c->ext_sampling_index);
                    if (c->ext_sample_rate == c->sample_rate)
                        c->sbr = -1;
                }
                if (get_bits_left(gb) > 11 && get_bits(gb, 11) == 0x548)
                    c->ps = get_bits1(gb);
                break;
            } else
                get_bits1(gb); // skip 1 bit
        }
    }
 
    //PS requires SBR
    if (!c->sbr)
        c->ps = 0;
    //Limit implicit PS to the HE-AACv2 Profile
    if ((c->ps == -1 && c->object_type != AOT_AAC_LC) || c->channels & ~0x01)
        c->ps = 0;
 
    return specific_config_bitindex - start_bit_index;
}
 
int avpriv_mpeg4audio_get_config2(MPEG4AudioConfig *c, const uint8_t *buf,
                                  int size, int sync_extension, void *logctx)
{
    GetBitContext gb;
    int ret;
 
    if (size <= 0)
        return AVERROR_INVALIDDATA;
 
    ret = init_get_bits8(&gb, buf, size);
    if (ret < 0)
        return ret;
 
    return ff_mpeg4audio_get_config_gb(c, &gb, sync_extension, logctx);
}