FFmpeg: AC3DSPContext Struct Reference

FFmpeg

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.

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

libavcodec/ac3dsp.h

Generated on Wed Aug 24 2022 21:38:54 for FFmpeg by doxygen 1.8.17