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Code Issues Releases Activity

WMAPRO: use some type punning in decode_coeffs()

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Originally committed as revision 20284 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Måns Rullgård 2009-10-18 18:51:54 +00:00
parent f122ef36b1
commit 4df254f1f1
1 changed files with 25 additions and 13 deletions
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38
libavcodec/wmaprodec.c
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@ -762,6 +762,15 @@ static int decode_channel_transform(WMAProDecodeCtx* s)
*/ */
static int decode_coeffs(WMAProDecodeCtx *s, int c) static int decode_coeffs(WMAProDecodeCtx *s, int c)
{ {
/* Integers 0..15 as single-precision floats. The table saves a
costly int to float conversion, and storing the values as
integers allows fast sign-flipping. */
static const int fval_tab[16] = {
0x00000000, 0x3f800000, 0x40000000, 0x40400000,
0x40800000, 0x40a00000, 0x40c00000, 0x40e00000,
0x41000000, 0x41100000, 0x41200000, 0x41300000,
0x41400000, 0x41500000, 0x41600000, 0x41700000,
};
int vlctable; int vlctable;
VLC* vlc; VLC* vlc;
WMAProChannelCtx* ci = &s->channel[c]; WMAProChannelCtx* ci = &s->channel[c];
@ -797,29 +806,32 @@ static int decode_coeffs(WMAProDecodeCtx *s, int c)
for (i = 0; i < 4; i += 2) { for (i = 0; i < 4; i += 2) {
idx = get_vlc2(&s->gb, vec2_vlc.table, VLCBITS, VEC2MAXDEPTH); idx = get_vlc2(&s->gb, vec2_vlc.table, VLCBITS, VEC2MAXDEPTH);
if (idx == HUFF_VEC2_SIZE - 1) { if (idx == HUFF_VEC2_SIZE - 1) {
vals[i] = get_vlc2(&s->gb, vec1_vlc.table, VLCBITS, VEC1MAXDEPTH); int v0, v1;
if (vals[i] == HUFF_VEC1_SIZE - 1) v0 = get_vlc2(&s->gb, vec1_vlc.table, VLCBITS, VEC1MAXDEPTH);
vals[i] += ff_wma_get_large_val(&s->gb); if (v0 == HUFF_VEC1_SIZE - 1)
vals[i+1] = get_vlc2(&s->gb, vec1_vlc.table, VLCBITS, VEC1MAXDEPTH); v0 += ff_wma_get_large_val(&s->gb);
if (vals[i+1] == HUFF_VEC1_SIZE - 1) v1 = get_vlc2(&s->gb, vec1_vlc.table, VLCBITS, VEC1MAXDEPTH);
vals[i+1] += ff_wma_get_large_val(&s->gb); if (v1 == HUFF_VEC1_SIZE - 1)
v1 += ff_wma_get_large_val(&s->gb);
((float*)vals)[i ] = v0;
((float*)vals)[i+1] = v1;
} else { } else {
vals[i] = symbol_to_vec2[idx] >> 4; vals[i] = fval_tab[symbol_to_vec2[idx] >> 4 ];
vals[i+1] = symbol_to_vec2[idx] & 0xF; vals[i+1] = fval_tab[symbol_to_vec2[idx] & 0xF];
} }
} }
} else { } else {
vals[0] = symbol_to_vec4[idx] >> 12; vals[0] = fval_tab[ symbol_to_vec4[idx] >> 12 ];
vals[1] = (symbol_to_vec4[idx] >> 8) & 0xF; vals[1] = fval_tab[(symbol_to_vec4[idx] >> 8) & 0xF];
vals[2] = (symbol_to_vec4[idx] >> 4) & 0xF; vals[2] = fval_tab[(symbol_to_vec4[idx] >> 4) & 0xF];
vals[3] = symbol_to_vec4[idx] & 0xF; vals[3] = fval_tab[ symbol_to_vec4[idx] & 0xF];
} }
/** decode sign */ /** decode sign */
for (i = 0; i < 4; i++) { for (i = 0; i < 4; i++) {
if (vals[i]) { if (vals[i]) {
int sign = get_bits1(&s->gb) - 1; int sign = get_bits1(&s->gb) - 1;
ci->coeffs[cur_coeff] = (vals[i] ^ sign) - sign; *(uint32_t*)&ci->coeffs[cur_coeff] = vals[i] ^ sign<<31;
num_zeros = 0; num_zeros = 0;
} else { } else {
ci->coeffs[cur_coeff] = 0; ci->coeffs[cur_coeff] = 0;