ffmpeg | branch: master | Marton Balint <c...@passwd.hu> | Mon Jan 6 21:18:36 2025 +0100| [ed26812337b397e602e68dae5c39b20b8b599565] | committer: Marton Balint
avcodec/mpegvideo_enc: fix qmat value comments The comments supposed to track the possible value of the qmat and qmat16 matrices, but they were not updated properly in the long history of the mpegvideo encoder. Also they wrongly assumed the usage of built-in quantizer matrices and linear quantization. Signed-off-by: Marton Balint <c...@passwd.hu> > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=ed26812337b397e602e68dae5c39b20b8b599565 --- libavcodec/mpegvideo_enc.c | 37 ++++++++++++++++++++----------------- 1 file changed, 20 insertions(+), 17 deletions(-) diff --git a/libavcodec/mpegvideo_enc.c b/libavcodec/mpegvideo_enc.c index b72e4a8cf2..d5088fe67f 100644 --- a/libavcodec/mpegvideo_enc.c +++ b/libavcodec/mpegvideo_enc.c @@ -133,11 +133,11 @@ void ff_convert_matrix(MpegEncContext *s, int (*qmat)[64], for (i = 0; i < 64; i++) { const int j = s->idsp.idct_permutation[i]; int64_t den = (int64_t) qscale2 * 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 */ + /* 1 * 1 <= qscale2 * quant_matrix[j] <= 112 * 255 + * Assume x = qscale2 * quant_matrix[j] + * 1 <= x <= 28560 + * (1 << 22) / 1 >= (1 << 22) / (x) >= (1 << 22) / 28560 + * 4194304 >= (1 << 22) / (x) >= 146 */ qmat[qscale][i] = (int)((UINT64_C(2) << QMAT_SHIFT) / den); } @@ -145,11 +145,11 @@ void ff_convert_matrix(MpegEncContext *s, int (*qmat)[64], for (i = 0; i < 64; i++) { const int j = s->idsp.idct_permutation[i]; int64_t den = ff_aanscales[i] * (int64_t) qscale2 * 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 */ + /* 1247 * 1 * 1 <= ff_aanscales[i] * qscale2 * quant_matrix[j] <= 31521 * 112 * 255 + * Assume x = ff_aanscales[i] * qscale2 * quant_matrix[j] + * 1247 <= x <= 900239760 + * (1 << 36) / 1247 >= (1 << 36) / (x) >= (1 << 36) / 900239760 + * 55107840 >= (1 << 36) / (x) >= 76 */ qmat[qscale][i] = (int)((UINT64_C(2) << (QMAT_SHIFT + 14)) / den); } @@ -157,14 +157,17 @@ void ff_convert_matrix(MpegEncContext *s, int (*qmat)[64], for (i = 0; i < 64; i++) { const int j = s->idsp.idct_permutation[i]; int64_t den = (int64_t) qscale2 * 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 */ + /* 1 * 1 <= qscale2 * quant_matrix[j] <= 112 * 255 + * Assume x = qscale2 * quant_matrix[j] + * 1 <= x <= 28560 + * (1 << 22) / 1 >= (1 << 22) / (x) >= (1 << 22) / 28560 + * 4194304 >= (1 << 22) / (x) >= 146 + * + * 1 <= x <= 28560 + * (1 << 17) / 1 >= (1 << 17) / (x) >= (1 << 17) / 28560 + * 131072 >= (1 << 17) / (x) >= 4 */ + qmat[qscale][i] = (int)((UINT64_C(2) << QMAT_SHIFT) / den); - //qmat [qscale][i] = (1 << QMAT_SHIFT_MMX) / - // (qscale * quant_matrix[i]); qmat16[qscale][0][i] = (2 << QMAT_SHIFT_MMX) / den; if (qmat16[qscale][0][i] == 0 || _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog To unsubscribe, visit link above, or email ffmpeg-cvslog-requ...@ffmpeg.org with subject "unsubscribe".
