tor-browser

mpeg4audio.c (5691B)

---

/*
* 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;
   }

   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);
}