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mpegvideo_enc: factor out denominator and explicitly cast operands

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CC: libav-stable@libav.org
Bug-Id: CID 608053
pull/94/head
Vittorio Giovara 10 years ago
parent e0a1d0a2b0
commit 0a66647061
1 changed files with 7 additions and 9 deletions
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  1. 16
      libavcodec/mpegvideo_enc.c

16
libavcodec/mpegvideo_enc.c
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@ -95,42 +95,40 @@ void ff_convert_matrix(MpegEncContext *s, int (*qmat)[64],
fdsp->fdct == ff_jpeg_fdct_islow_10) {
for (i = 0; i < 64; i++) {
const int j = s->idsp.idct_permutation[i];
int64_t den = (int64_t) qscale * quant_matrix[j];
/* 16 <= qscale * quant_matrix[i] <= 7905
* Assume x = ff_aanscales[i] * qscale * quant_matrix[i]
* 19952 <= x <= 249205026
* (1 << 36) / 19952 >= (1 << 36) / (x) >= (1 << 36) / 249205026
* 3444240 >= (1 << 36) / (x) >= 275 */
qmat[qscale][i] = (int)((UINT64_C(1) << QMAT_SHIFT) /
(qscale * quant_matrix[j]));
qmat[qscale][i] = (int)((UINT64_C(1) << QMAT_SHIFT) / den);
}
} else if (fdsp->fdct == ff_fdct_ifast) {
for (i = 0; i < 64; i++) {
const int j = s->idsp.idct_permutation[i];
int64_t den = ff_aanscales[i] * (int64_t) qscale * quant_matrix[j];
/* 16 <= qscale * quant_matrix[i] <= 7905
* Assume x = ff_aanscales[i] * qscale * quant_matrix[i]
* 19952 <= x <= 249205026
* (1 << 36) / 19952 >= (1 << 36) / (x) >= (1 << 36) / 249205026
* 3444240 >= (1 << 36) / (x) >= 275 */
qmat[qscale][i] = (int)((UINT64_C(1) << (QMAT_SHIFT + 14)) /
(ff_aanscales[i] * qscale *
quant_matrix[j]));
qmat[qscale][i] = (int)((UINT64_C(1) << (QMAT_SHIFT + 14)) / den);
}
} else {
for (i = 0; i < 64; i++) {
const int j = s->idsp.idct_permutation[i];
int64_t den = (int64_t) qscale * quant_matrix[j];
/* We can safely suppose that 16 <= quant_matrix[i] <= 255
* Assume x = qscale * quant_matrix[i]
* So 16 <= x <= 7905
* so (1 << 19) / 16 >= (1 << 19) / (x) >= (1 << 19) / 7905
* so 32768 >= (1 << 19) / (x) >= 67 */
qmat[qscale][i] = (int)((UINT64_C(1) << QMAT_SHIFT) /
(qscale * quant_matrix[j]));
qmat[qscale][i] = (int)((UINT64_C(1) << QMAT_SHIFT) / den);
//qmat [qscale][i] = (1 << QMAT_SHIFT_MMX) /
// (qscale * quant_matrix[i]);
qmat16[qscale][0][i] = (1 << QMAT_SHIFT_MMX) /
(qscale * quant_matrix[j]);
qmat16[qscale][0][i] = (1 << QMAT_SHIFT_MMX) / den;
if (qmat16[qscale][0][i] == 0 ||
qmat16[qscale][0][i] == 128 * 256)

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