libavcodec/ra144enc.c File Reference

Real Audio 1.0 (14.4K) encoder. More...

#include <float.h>
#include "avcodec.h"
#include "put_bits.h"
#include "celp_filters.h"
#include "ra144.h"

Go to the source code of this file.

Functions

static av_cold int ra144_encode_init (AVCodecContext *avctx)
static av_cold int ra144_encode_close (AVCodecContext *avctx)
static int quantize (int value, const int16_t *table, unsigned int size)
 Quantize a value by searching a sorted table for the element with the nearest value.
static void orthogonalize (float *v, const float *u)
 Orthogonalize a vector to another vector.
static void get_match_score (float *work, const float *coefs, float *vect, const float *ortho1, const float *ortho2, const float *data, float *score, float *gain)
 Calculate match score and gain of an LPC-filtered vector with respect to input data, possibly othogonalizing it to up to 2 other vectors.
static void create_adapt_vect (float *vect, const int16_t *cb, int lag)
 Create a vector from the adaptive codebook at a given lag value.
static int adaptive_cb_search (const int16_t *adapt_cb, float *work, const float *coefs, float *data)
 Search the adaptive codebook for the best entry and gain and remove its contribution from input data.
static void find_best_vect (float *work, const float *coefs, const int8_t cb[][BLOCKSIZE], const float *ortho1, const float *ortho2, float *data, int *idx, float *gain)
 Find the best vector of a fixed codebook by applying an LPC filter to codebook entries, possibly othogonalizing them to up to 2 other vectors and matching the results with input data.
static void fixed_cb_search (float *work, const float *coefs, float *data, int cba_idx, int *cb1_idx, int *cb2_idx)
 Search the two fixed codebooks for the best entry and gain.
static void ra144_encode_subblock (RA144Context *ractx, const int16_t *sblock_data, const int16_t *lpc_coefs, unsigned int rms, PutBitContext *pb)
 Encode a subblock of the current frame.
static int ra144_encode_frame (AVCodecContext *avctx, uint8_t *frame, int buf_size, void *data)

Variables

AVCodec ff_ra_144_encoder


Detailed Description

Real Audio 1.0 (14.4K) encoder.

Author:
Francesco Lavra <francescolavra@interfree.it>

Definition in file ra144enc.c.


Function Documentation

static int adaptive_cb_search ( const int16_t *  adapt_cb,
float *  work,
const float *  coefs,
float *  data 
) [static]

Search the adaptive codebook for the best entry and gain and remove its contribution from input data.

Parameters:
adapt_cb array from which the adaptive codebook is extracted
work array used to calculate LPC-filtered vectors
coefs coefficients of the LPC filter
data input data
Returns:
index of the best entry of the adaptive codebook

Re-calculate the filtered vector from the vector with maximum match score and remove its contribution from input data.

Definition at line 189 of file ra144enc.c.

Referenced by ra144_encode_subblock().

static void create_adapt_vect ( float *  vect,
const int16_t *  cb,
int  lag 
) [static]

Create a vector from the adaptive codebook at a given lag value.

Parameters:
vect array where vector is stored
cb adaptive codebook
lag lag value

Definition at line 166 of file ra144enc.c.

Referenced by adaptive_cb_search().

static void find_best_vect ( float *  work,
const float *  coefs,
const int8_t  cb[][BLOCKSIZE],
const float *  ortho1,
const float *  ortho2,
float *  data,
int *  idx,
float *  gain 
) [static]

Find the best vector of a fixed codebook by applying an LPC filter to codebook entries, possibly othogonalizing them to up to 2 other vectors and matching the results with input data.

Parameters:
work array used to calculate the filtered vectors
coefs coefficients of the LPC filter
cb fixed codebook
ortho1 first vector against which orthogonalization is performed
ortho2 second vector against which orthogonalization is performed
data input data
idx pointer to variable where the index of the best codebook entry is returned
gain pointer to variable where the gain of the best codebook entry is returned

Definition at line 237 of file ra144enc.c.

Referenced by fixed_cb_search().

static void fixed_cb_search ( float *  work,
const float *  coefs,
float *  data,
int  cba_idx,
int *  cb1_idx,
int *  cb2_idx 
) [static]

Search the two fixed codebooks for the best entry and gain.

Parameters:
work array used to calculate LPC-filtered vectors
coefs coefficients of the LPC filter
data input data
cba_idx index of the best entry of the adaptive codebook
cb1_idx pointer to variable where the index of the best entry of the first fixed codebook is returned
cb2_idx pointer to variable where the index of the best entry of the second fixed codebook is returned

The filtered vector from the adaptive codebook can be retrieved from work, because this function is called just after adaptive_cb_search().

Re-calculate the filtered vector from the vector with maximum match score and remove its contribution from input data.

Definition at line 272 of file ra144enc.c.

Referenced by ra144_encode_subblock().

static void get_match_score ( float *  work,
const float *  coefs,
float *  vect,
const float *  ortho1,
const float *  ortho2,
const float *  data,
float *  score,
float *  gain 
) [static]

Calculate match score and gain of an LPC-filtered vector with respect to input data, possibly othogonalizing it to up to 2 other vectors.

Parameters:
work array used to calculate the filtered vector
coefs coefficients of the LPC filter
vect original vector
ortho1 first vector against which orthogonalization is performed
ortho2 second vector against which orthogonalization is performed
data input data
score pointer to variable where match score is returned
gain pointer to variable where gain is returned

Definition at line 133 of file ra144enc.c.

Referenced by adaptive_cb_search(), and find_best_vect().

static void orthogonalize ( float *  v,
const float *  u 
) [static]

Orthogonalize a vector to another vector.

Parameters:
v vector to orthogonalize
u vector against which orthogonalization is performed

Definition at line 105 of file ra144enc.c.

Referenced by fixed_cb_search(), and get_match_score().

static int quantize ( int  value,
const int16_t *  table,
unsigned int  size 
) [static]

Quantize a value by searching a sorted table for the element with the nearest value.

Parameters:
value value to quantize
table array containing the quantization table
size size of the quantization table
Returns:
index of the quantization table corresponding to the element with the nearest value

Definition at line 80 of file ra144enc.c.

static av_cold int ra144_encode_close ( AVCodecContext avctx  )  [static]

Definition at line 62 of file ra144enc.c.

static int ra144_encode_frame ( AVCodecContext avctx,
uint8_t *  frame,
int  buf_size,
void *  data 
) [static]

< reflection coefficients of the frame

< RMS of the reflection coefficients

Since the LPC coefficients are calculated on a frame centered over the fourth subframe, to encode a given frame, data from the next frame is needed. In each call to this function, the previous frame (whose data are saved in the encoder context) is encoded, and data from the current frame are saved in the encoder context to be used in the next function call.

TODO: apply perceptual weighting of the input speech through bandwidth expansion of the LPC filter.

The filter is unstable: use the coefficients of the previous frame.

Definition at line 422 of file ra144enc.c.

static av_cold int ra144_encode_init ( AVCodecContext avctx  )  [static]

Definition at line 36 of file ra144enc.c.

static void ra144_encode_subblock ( RA144Context ractx,
const int16_t *  sblock_data,
const int16_t *  lpc_coefs,
unsigned int  rms,
PutBitContext pb 
) [static]

Encode a subblock of the current frame.

Parameters:
ractx encoder context
sblock_data input data of the subblock
lpc_coefs coefficients of the LPC filter
rms RMS of the reflection coefficients
pb pointer to PutBitContext of the current frame

Calculate the zero-input response of the LPC filter and subtract it from input data.

Codebook search is performed without taking into account the contribution of the previous subblock, since it has been just subtracted from input data.

The filtered vector from the adaptive codebook can be retrieved from work, see implementation of adaptive_cb_search().

Definition at line 321 of file ra144enc.c.

Referenced by ra144_encode_frame().


Variable Documentation

Initial value:

{
    "real_144",
    AVMEDIA_TYPE_AUDIO,
    CODEC_ID_RA_144,
    sizeof(RA144Context),
    ra144_encode_init,
    ra144_encode_frame,
    ra144_encode_close,
    .long_name = NULL_IF_CONFIG_SMALL("RealAudio 1.0 (14.4K) encoder"),
}

Definition at line 511 of file ra144enc.c.


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