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Separate window function from autocorrelation.

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Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Justin Ruggles
2011-01-21 00:12:03 +00:00
committed by Mans Rullgard
parent 56f8952b25
commit 77a78e9bdc
6 changed files with 99 additions and 39 deletions
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57
libavcodec/lpc.c
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@ -28,7 +28,7 @@
/**
* Apply Welch window function to audio block
*/
static void apply_welch_window(const int32_t *data, int len, double *w_data)
static void apply_welch_window_c(const int32_t *data, int len, double *w_data)
{
int i, n2;
double w;
@ -54,24 +54,16 @@ static void apply_welch_window(const int32_t *data, int len, double *w_data)
* Calculate autocorrelation data from audio samples
* A Welch window function is applied before calculation.
*/
static void lpc_compute_autocorr_c(const int32_t *data, int len, int lag,
static void lpc_compute_autocorr_c(const double *data, int len, int lag,
double *autoc)
{
int i, j;
double tmp[len + lag + 1];
double *data1= tmp + lag;
apply_welch_window(data, len, data1);
for(j=0; j<lag; j++)
data1[j-lag]= 0.0;
data1[len] = 0.0;
for(j=0; j<lag; j+=2){
double sum0 = 1.0, sum1 = 1.0;
for(i=j; i<len; i++){
sum0 += data1[i] * data1[i-j];
sum1 += data1[i] * data1[i-j-1];
sum0 += data[i] * data[i-j];
sum1 += data[i] * data[i-j-1];
}
autoc[j ] = sum0;
autoc[j+1] = sum1;
@ -80,8 +72,8 @@ static void lpc_compute_autocorr_c(const int32_t *data, int len, int lag,
if(j==lag){
double sum = 1.0;
for(i=j-1; i<len; i+=2){
sum += data1[i ] * data1[i-j ]
+ data1[i+1] * data1[i-j+1];
sum += data[i ] * data[i-j ]
+ data[i+1] * data[i-j+1];
}
autoc[j] = sum;
}
@ -177,8 +169,19 @@ int ff_lpc_calc_coefs(LPCContext *s,
assert(max_order >= MIN_LPC_ORDER && max_order <= MAX_LPC_ORDER &&
lpc_type > AV_LPC_TYPE_FIXED);
/* reinit LPC context if parameters have changed */
if (blocksize != s->blocksize || max_order != s->max_order ||
lpc_type != s->lpc_type) {
ff_lpc_end(s);
ff_lpc_init(s, blocksize, max_order, lpc_type);
}
if (lpc_type == AV_LPC_TYPE_LEVINSON) {
s->lpc_compute_autocorr(samples, blocksize, max_order, autoc);
double *windowed_samples = s->windowed_samples + max_order;
s->lpc_apply_welch_window(samples, blocksize, windowed_samples);
s->lpc_compute_autocorr(windowed_samples, blocksize, max_order, autoc);
compute_lpc_coefs(autoc, max_order, &lpc[0][0], MAX_LPC_ORDER, 0, 1);
@ -236,10 +239,32 @@ int ff_lpc_calc_coefs(LPCContext *s,
return opt_order;
}
av_cold void ff_lpc_init(LPCContext *s)
av_cold int ff_lpc_init(LPCContext *s, int blocksize, int max_order,
enum AVLPCType lpc_type)
{
s->blocksize = blocksize;
s->max_order = max_order;
s->lpc_type = lpc_type;
if (lpc_type == AV_LPC_TYPE_LEVINSON) {
s->windowed_samples = av_mallocz((blocksize + max_order + 2) *
sizeof(*s->windowed_samples));
if (!s->windowed_samples)
return AVERROR(ENOMEM);
} else {
s->windowed_samples = NULL;
}
s->lpc_apply_welch_window = apply_welch_window_c;
s->lpc_compute_autocorr = lpc_compute_autocorr_c;
if (HAVE_MMX)
ff_lpc_init_x86(s);
return 0;
}
av_cold void ff_lpc_end(LPCContext *s)
{
av_freep(&s->windowed_samples);
}