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simplify transform 

Originally committed as revision 12848 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2008-04-16 13:28:13 +00:00
parent d965c3e7bc
commit e616c6d612
1 changed files with 10 additions and 20 deletions
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30
libavcodec/nellymoserdec.c
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@ -111,30 +111,22 @@ static inline int signed_shift(int i, int shift) {
return i >> -shift;
}
static void overlap_and_window(NellyMoserDecodeContext *s, float *state, float *audio)
static void overlap_and_window(NellyMoserDecodeContext *s, float *state, float *audio, float *a_in)
{
int bot, mid_up, mid_down, top;
float s_bot, s_top;
int bot, top, top2;
bot = 0;
top = NELLY_BUF_LEN-1;
mid_up = NELLY_BUF_LEN/2;
mid_down = (NELLY_BUF_LEN/2)-1;
top2 = 2*NELLY_BUF_LEN-1;
while (bot < NELLY_BUF_LEN/4) {
s_bot = audio[bot];
s_top = -audio[top];
audio[bot] = (-audio[mid_up]*sine_window[bot]-state[bot ]*sine_window[top])/s->scale_bias + s->add_bias;
audio[top] = (-state[bot ]*sine_window[bot]+audio[mid_up]*sine_window[top])/s->scale_bias + s->add_bias;
state[bot] = audio[mid_down];
audio[mid_down] = (s_top *sine_window[mid_down]-state[mid_down]*sine_window[mid_up])/s->scale_bias + s->add_bias;
audio[mid_up ] = (-state[mid_down]*sine_window[mid_down]-s_top *sine_window[mid_up])/s->scale_bias + s->add_bias;
state[mid_down] = s_bot;
while (bot < NELLY_BUF_LEN/2) {
audio[bot] = (- a_in[bot]*sine_window[bot]-state[bot]*sine_window[top])/s->scale_bias;
audio[top] = (-state[bot]*sine_window[bot]+ a_in[bot]*sine_window[top])/s->scale_bias;
state[bot] = a_in[top2];
bot++;
mid_up++;
mid_down--;
top2--;
top--;
}
}
@ -323,9 +315,7 @@ void nelly_decode_block(NellyMoserDecodeContext *s, const unsigned char block[NE
aptr, s->imdct_tmp);
/* XXX: overlapping and windowing should be part of a more
generic imdct function */
memcpy(&aptr[0],&s->imdct_out[NELLY_BUF_LEN+NELLY_BUF_LEN/2], (NELLY_BUF_LEN/2)*sizeof(float));
memcpy(&aptr[NELLY_BUF_LEN / 2],&s->imdct_out[0],(NELLY_BUF_LEN/2)*sizeof(float));
overlap_and_window(s, s->state, aptr);
overlap_and_window(s, s->state, aptr, s->imdct_out);
}
}