AC3DSPContext Struct Reference

#include <ac3dsp.h>

Data Fields
void(*	ac3_exponent_min )(uint8_t *exp, int num_reuse_blocks, int nb_coefs)
	Set each encoded exponent in a block to the minimum of itself and the exponents in the same frequency bin of up to 5 following blocks. More...
void(*	float_to_fixed24 )(int32_t *dst, const float *src, unsigned int len)
	Convert an array of float in range [-1.0,1.0] to int32_t with range [-(1<<24),(1<<24)]. More...
void(*	bit_alloc_calc_bap )(int16_t *mask, int16_t *psd, int start, int end, int snr_offset, int floor, const uint8_t *bap_tab, uint8_t *bap)
	Calculate bit allocation pointers. More...
void(*	update_bap_counts )(uint16_t mant_cnt[16], uint8_t *bap, int len)
	Update bap counts using the supplied array of bap. More...
int(*	compute_mantissa_size )(uint16_t mant_cnt[6][16])
	Calculate the number of bits needed to encode a set of mantissas. More...
void(*	extract_exponents )(uint8_t *exp, int32_t *coef, int nb_coefs)
void(*	sum_square_butterfly_int32 )(int64_t sum[4], const int32_t *coef0, const int32_t *coef1, int len)
void(*	sum_square_butterfly_float )(float sum[4], const float *coef0, const float *coef1, int len)
int	out_channels
int	in_channels
void(*	downmix )(float **samples, float **matrix, int len)
void(*	downmix_fixed )(int32_t **samples, int16_t **matrix, int len)

Detailed Description

Definition at line 33 of file ac3dsp.h.

Field Documentation

ac3_exponent_min

void(* AC3DSPContext::ac3_exponent_min) (uint8_t *exp, int num_reuse_blocks, int nb_coefs)

Set each encoded exponent in a block to the minimum of itself and the exponents in the same frequency bin of up to 5 following blocks.

Parameters

exp	pointer to the start of the current block of exponents. constraints: align 16
num_reuse_blocks	number of blocks that will reuse exponents from the current block. constraints: range 0 to 5
nb_coefs	number of frequency coefficients.

Definition at line 43 of file ac3dsp.h.

float_to_fixed24

void(* AC3DSPContext::float_to_fixed24) (int32_t *dst, const float *src, unsigned int len)

Convert an array of float in range [-1.0,1.0] to int32_t with range [-(1<<24),(1<<24)].

Parameters

dst	destination array of int32_t. constraints: 16-byte aligned
src	source array of float. constraints: 16-byte aligned
len	number of elements to convert. constraints: multiple of 32 greater than zero

Definition at line 56 of file ac3dsp.h.

bit_alloc_calc_bap

void(* AC3DSPContext::bit_alloc_calc_bap) (int16_t *mask, int16_t *psd, int start, int end, int snr_offset, int floor, const uint8_t *bap_tab, uint8_t *bap)

Calculate bit allocation pointers.

The SNR is the difference between the masking curve and the signal. AC-3 uses this value for each frequency bin to allocate bits. The snroffset parameter is a global adjustment to the SNR for all bins.

Parameters

[in]	mask	masking curve
[in]	psd	signal power for each frequency bin
[in]	start	starting bin location
[in]	end	ending bin location
[in]	snr_offset	SNR adjustment
[in]	floor	noise floor
[in]	bap_tab	look-up table for bit allocation pointers
[out]	bap	bit allocation pointers

Definition at line 73 of file ac3dsp.h.

update_bap_counts

void(* AC3DSPContext::update_bap_counts) (uint16_t mant_cnt[16], uint8_t *bap, int len)

Update bap counts using the supplied array of bap.

Parameters

[out]	mant_cnt	bap counts for 1 block
[in]	bap	array of bap, pointing to start coef bin
[in]	len	number of elements to process

Definition at line 84 of file ac3dsp.h.

compute_mantissa_size

int(* AC3DSPContext::compute_mantissa_size) (uint16_t mant_cnt[6][16])

Calculate the number of bits needed to encode a set of mantissas.

Parameters

[in]

mant_cnt

bap counts for all blocks

Returns

mantissa bit count

Definition at line 92 of file ac3dsp.h.

extract_exponents

void(* AC3DSPContext::extract_exponents) (uint8_t *exp, int32_t *coef, int nb_coefs)

Definition at line 94 of file ac3dsp.h.

sum_square_butterfly_int32

void(* AC3DSPContext::sum_square_butterfly_int32) (int64_t sum[4], const int32_t *coef0, const int32_t *coef1, int len)

Definition at line 96 of file ac3dsp.h.

sum_square_butterfly_float

void(* AC3DSPContext::sum_square_butterfly_float) (float sum[4], const float *coef0, const float *coef1, int len)

Definition at line 99 of file ac3dsp.h.

out_channels

int AC3DSPContext::out_channels

Definition at line 102 of file ac3dsp.h.

in_channels

int AC3DSPContext::in_channels

Definition at line 103 of file ac3dsp.h.

downmix

void(* AC3DSPContext::downmix) (float **samples, float **matrix, int len)

Definition at line 104 of file ac3dsp.h.

downmix_fixed

void(* AC3DSPContext::downmix_fixed) (int32_t **samples, int16_t **matrix, int len)

Definition at line 105 of file ac3dsp.h.

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The documentation for this struct was generated from the following file:

• libavcodec/ac3dsp.h