diff options
Diffstat (limited to 'thirdparty/libtheora/quant.c')
| -rw-r--r-- | thirdparty/libtheora/quant.c | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/thirdparty/libtheora/quant.c b/thirdparty/libtheora/quant.c index 8359f5abea..e206202844 100644 --- a/thirdparty/libtheora/quant.c +++ b/thirdparty/libtheora/quant.c @@ -11,7 +11,7 @@ ******************************************************************** function: - last mod: $Id: quant.c 16503 2009-08-22 18:14:02Z giles $ + last mod: $Id$ ********************************************************************/ @@ -21,6 +21,14 @@ #include "quant.h" #include "decint.h" +/*The maximum output of the DCT with +/- 255 inputs is +/- 8157. + These minimum quantizers ensure the result after quantization (and after + prediction for DC) will be no more than +/- 510. + The tokenization system can handle values up to +/- 580, so there is no need + to do any coefficient clamping. + I would rather have allowed smaller quantizers and had to clamp, but these + minimums were required when constructing the original VP3 matrices and have + been formalized in the spec.*/ static const unsigned OC_DC_QUANT_MIN[2]={4<<2,8<<2}; static const unsigned OC_AC_QUANT_MIN[2]={2<<2,4<<2}; |