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.
int(* ac3_max_msb_abs_int16 )(const int16_t *src, int len)
Calculate the maximum MSB of the absolute value of each element in an array of int16_t.
void(* ac3_lshift_int16 )(int16_t *src, unsigned int len, unsigned int shift)
Left-shift each value in an array of int16_t by a specified amount.
void(* ac3_rshift_int32 )(int32_t *src, unsigned int len, unsigned int shift)
Right-shift each value in an array of int32_t by a specified amount.
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)].
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.
void(* update_bap_counts )(uint16_t mant_cnt[16], uint8_t *bap, int len)
Update bap counts using the supplied array of bap.
int(* compute_mantissa_size )(uint16_t mant_cnt[6][16])
Calculate the number of bits needed to encode a set of mantissas.
void(* extract_exponents )(uint8_t *exp, int32_t *coef, int nb_coefs)

Detailed Description

Definition at line 33 of file ac3dsp.h.

Field Documentation

 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.

Referenced by encode_exponents(), ff_ac3dsp_init(), ff_ac3dsp_init_arm(), and ff_ac3dsp_init_x86().

 void(* AC3DSPContext::ac3_lshift_int16)(int16_t *src, unsigned int len, unsigned int shift)

Left-shift each value in an array of int16_t by a specified amount.

Parameters:
 src input array constraints: align 16 len number of values in the array constraints: multiple of 32 greater than 0 shift left shift amount constraints: range [0,15]

Referenced by ff_ac3dsp_init(), ff_ac3dsp_init_arm(), and ff_ac3dsp_init_x86().

 int(* AC3DSPContext::ac3_max_msb_abs_int16)(const int16_t *src, int len)

Calculate the maximum MSB of the absolute value of each element in an array of int16_t.

Parameters:
 src input array constraints: align 16. values must be in range [-32767,32767] len number of values in the array constraints: multiple of 16 greater than 0
Returns:
a value with the same MSB as max(abs(src[]))

Referenced by ff_ac3dsp_init(), ff_ac3dsp_init_arm(), ff_ac3dsp_init_x86(), and log2_tab().

 void(* AC3DSPContext::ac3_rshift_int32)(int32_t *src, unsigned int len, unsigned int shift)

Right-shift each value in an array of int32_t by a specified amount.

Parameters:
 src input array constraints: align 16 len number of values in the array constraints: multiple of 16 greater than 0 shift right shift amount constraints: range [0,31]

Referenced by ff_ac3dsp_init(), ff_ac3dsp_init_arm(), and ff_ac3dsp_init_x86().

 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

Referenced by bit_alloc(), decode_audio_block(), ff_ac3dsp_init(), and ff_ac3dsp_init_arm().

 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

Referenced by count_mantissa_bits(), ff_ac3dsp_init(), and ff_ac3dsp_init_x86().

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

 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

 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

Referenced by count_mantissa_bits_update_ch(), ff_ac3dsp_init(), and ff_ac3dsp_init_arm().

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

Generated on Fri Oct 26 02:39:50 2012 for FFmpeg by  1.5.8