mpeg4audio.c File Reference

#include "bitstream.h"
#include "mpeg4audio.h"

Go to the source code of this file.

Functions
static int	get_object_type (GetBitContext *gb)
static int	get_sample_rate (GetBitContext *gb, int *index)
int	ff_mpeg4audio_get_config (MPEG4AudioConfig *c, const uint8_t *buf, int buf_size)
Variables
const int	ff_mpeg4audio_sample_rates [16]
const uint8_t	ff_mpeg4audio_channels [8]

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Function Documentation

int ff_mpeg4audio_get_config	(	MPEG4AudioConfig *	c,
		const uint8_t *	buf,
		int	buf_size
	)

Parse MPEG-4 systems extradata to retrieve audio configuration.

Parameters:

[in]	c	MPEG4AudioConfig structure to fill.
[in]	buf	Extradata from container.
[in]	buf_size	Extradata size.

Returns:

On error -1 is returned, on success AudioSpecificConfig bit index in extradata.

Definition at line 49 of file mpeg4audio.c.

References c, get_bits(), get_bits1(), get_bits_count(), get_object_type(), get_sample_rate(), init_get_bits(), and show_bits().

Referenced by mov_read_esds().

{
    GetBitContext gb;
    int specific_config_bitindex;

    init_get_bits(&gb, buf, buf_size*8);
    c->object_type = get_object_type(&gb);
    c->sample_rate = get_sample_rate(&gb, &c->sampling_index);
    c->chan_config = get_bits(&gb, 4);
    c->sbr = -1;
    if (c->object_type == 5) {
        c->ext_object_type = c->object_type;
        c->sbr = 1;
        c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
        c->object_type = get_object_type(&gb);
    } else
        c->ext_object_type = 0;

    specific_config_bitindex = get_bits_count(&gb);

    if (c->ext_object_type != 5) {
        int bits_left = buf_size*8 - specific_config_bitindex;
        for (; bits_left > 15; bits_left--) {
            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 == 5 && (c->sbr = get_bits1(&gb)) == 1)
                    c->ext_sample_rate = get_sample_rate(&gb, &c->ext_sampling_index);
                break;
            } else
                get_bits1(&gb); // skip 1 bit
        }
    }
    return specific_config_bitindex;
}

static int get_object_type

(

GetBitContext *

gb

)

[inline, static]

Definition at line 34 of file mpeg4audio.c.

References get_bits().

Referenced by ff_mpeg4audio_get_config().

{
    int object_type = get_bits(gb, 5);
    if (object_type == 31)
        object_type = 32 + get_bits(gb, 6);
    return object_type;
}

static int get_sample_rate	(	GetBitContext *	gb,
		int *	index
	)			[inline, static]

Definition at line 42 of file mpeg4audio.c.

References ff_mpeg4audio_sample_rates, and get_bits().

Referenced by ff_mpeg4audio_get_config().

{
    *index = get_bits(gb, 4);
    return *index == 0x0f ? get_bits(gb, 24) :
        ff_mpeg4audio_sample_rates[*index];
}

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Variable Documentation

const uint8_t ff_mpeg4audio_channels[8]

Initial value:

 {
    0, 1, 2, 3, 4, 5, 6, 8
}

Definition at line 30 of file mpeg4audio.c.

Referenced by aac_sync(), and mov_read_esds().

const int ff_mpeg4audio_sample_rates[16]

Initial value:

 {
    96000, 88200, 64000, 48000, 44100, 32000,
    24000, 22050, 16000, 12000, 11025, 8000, 7350
}

Definition at line 25 of file mpeg4audio.c.

Referenced by aac_sync(), get_aac_sample_rates(), get_sample_rate(), and matroska_aac_sri().

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