From 40116978de50c41b1e63ba6434f0d562cf173785 Mon Sep 17 00:00:00 2001 From: Dan Maas Date: Tue, 28 Feb 2006 02:54:48 +0000 Subject: Assign class 2 to most macroblocks by default, instead of a more conservative method defined by SMPTE Patch by Dan Maas Originally committed as revision 5074 to svn://svn.ffmpeg.org/ffmpeg/trunk --- libavcodec/dv.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) (limited to 'libavcodec/dv.c') diff --git a/libavcodec/dv.c b/libavcodec/dv.c index 9c315705bc..d4661fec5d 100644 --- a/libavcodec/dv.c +++ b/libavcodec/dv.c @@ -658,8 +658,22 @@ static always_inline void dv_set_class_number(DCTELEM* blk, EncBlockInfo* bi, const uint8_t* zigzag_scan, const int *weight, int bias) { int i, area; + /* We offer two different methods for class number assignment: the + method suggested in SMPTE 314M Table 22, and an improved + method. The SMPTE method is very conservative; it assigns class + 3 (i.e. severe quantization) to any block where the largest AC + component is greater than 36. ffmpeg's DV encoder tracks AC bit + consumption precisely, so there is no need to bias most blocks + towards strongly lossy compression. Instead, we assign class 2 + to most blocks, and use class 3 only when strictly necessary + (for blocks whose largest AC component exceeds 255). */ + +#if 0 /* SMPTE spec method */ static const int classes[] = {12, 24, 36, 0xffff}; - int max=12; +#else /* improved ffmpeg method */ + static const int classes[] = {-1, -1, 255, 0xffff}; +#endif + int max=classes[0]; int prev=0; bi->mb[0] = blk[0]; -- cgit v1.2.3