From 34790165dcdd438d9b12b78733740d240af56a65 Mon Sep 17 00:00:00 2001
From: Michael Niedermayer <michaelni@gmx.at>
Date: Sun, 12 Oct 2003 14:01:53 +0000
Subject: [PATCH] intra dc treshold != 0 decoding fixed

Originally committed as revision 2363 to svn://svn.ffmpeg.org/ffmpeg/trunk
---
 libavcodec/h263.c      | 26 ++++++++++++++++++++------
 libavcodec/mpeg4data.h |  4 ++++
 libavcodec/mpegvideo.h |  1 +
 3 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/libavcodec/h263.c b/libavcodec/h263.c
index 06b70d07fc..0acbe65cfa 100644
--- a/libavcodec/h263.c
+++ b/libavcodec/h263.c
@@ -3942,6 +3942,7 @@ static inline int mpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
     //Note intra & rvlc should be optimized away if this is inlined
     
     if(intra) {
+      if(s->qscale < s->intra_dc_threshold){
 	/* DC coef */
         if(s->partitioned_frame){
             level = s->dc_val[0][ s->block_index[n] ];
@@ -3955,6 +3956,9 @@ static inline int mpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
         }
         block[0] = level;
         i = 0;
+      }else{
+            i = -1;
+      }  
         if (!coded) 
             goto not_coded;
         
@@ -4154,7 +4158,19 @@ static inline int mpeg4_decode_block(MpegEncContext * s, DCTELEM * block,
     CLOSE_READER(re, &s->gb);
   }
  not_coded:
-    if (s->mb_intra) {
+    if (intra) {
+        if(s->qscale >= s->intra_dc_threshold){
+            uint16_t *dc_val;
+            block[0] += ff_mpeg4_pred_dc(s, n, &dc_val, &dc_pred_dir);
+            if (n < 4) {
+                *dc_val = block[0] * s->y_dc_scale;
+            } else {
+                *dc_val = block[0] * s->c_dc_scale;
+            }
+
+            if(i == -1) i=0;
+        }
+
         mpeg4_pred_ac(s, block, n, dc_pred_dir);
         if (s->ac_pred) {
             i = 63; /* XXX: not optimal */
@@ -5013,9 +5029,7 @@ static int decode_vop_header(MpegEncContext *s, GetBitContext *gb){
 //FIXME complexity estimation stuff
      
      if (s->shape != BIN_ONLY_SHAPE) {
-         int t;
-         t=get_bits(gb, 3); /* intra dc VLC threshold */
-//printf("threshold %d\n", t);
+         s->intra_dc_threshold= mpeg4_dc_threshold[ get_bits(gb, 3) ];
          if(!s->progressive_sequence){
              s->top_field_first= get_bits1(gb);
              s->alternate_scan= get_bits1(gb);
@@ -5063,12 +5077,12 @@ static int decode_vop_header(MpegEncContext *s, GetBitContext *gb){
              s->b_code=1;
 
          if(s->avctx->debug&FF_DEBUG_PICT_INFO){
-             printf("qp:%d fc:%d,%d %s size:%d pro:%d alt:%d top:%d %spel part:%d resync:%d w:%d a:%d rnd:%d vot:%d%s\n", 
+             printf("qp:%d fc:%d,%d %s size:%d pro:%d alt:%d top:%d %spel part:%d resync:%d w:%d a:%d rnd:%d vot:%d%s dc:%d\n", 
                  s->qscale, s->f_code, s->b_code, 
                  s->pict_type == I_TYPE ? "I" : (s->pict_type == P_TYPE ? "P" : (s->pict_type == B_TYPE ? "B" : "S")), 
                  gb->size_in_bits,s->progressive_sequence, s->alternate_scan, s->top_field_first, 
                  s->quarter_sample ? "q" : "h", s->data_partitioning, s->resync_marker, s->num_sprite_warping_points,
-                 s->sprite_warping_accuracy, 1-s->no_rounding, s->vo_type, s->vol_control_parameters ? " VOLC" : " "); 
+                 s->sprite_warping_accuracy, 1-s->no_rounding, s->vo_type, s->vol_control_parameters ? " VOLC" : " ", s->intra_dc_threshold); 
          }
 
          if(!s->scalability){
diff --git a/libavcodec/mpeg4data.h b/libavcodec/mpeg4data.h
index 8dc8c9deea..d48e874687 100644
--- a/libavcodec/mpeg4data.h
+++ b/libavcodec/mpeg4data.h
@@ -395,3 +395,7 @@ uint8_t ff_mpeg4_c_dc_scale_table[32]={
 const uint16_t ff_mpeg4_resync_prefix[8]={
     0x7F00, 0x7E00, 0x7C00, 0x7800, 0x7000, 0x6000, 0x4000, 0x0000
 };
+
+static const uint8_t mpeg4_dc_threshold[8]={
+    99, 13, 15, 17, 19, 21, 23, 0
+};
diff --git a/libavcodec/mpegvideo.h b/libavcodec/mpegvideo.h
index f1813f7568..69964e1cfd 100644
--- a/libavcodec/mpegvideo.h
+++ b/libavcodec/mpegvideo.h
@@ -566,6 +566,7 @@ typedef struct MpegEncContext {
     int low_delay;                   ///< no reordering needed / has no b-frames 
     int vo_type;
     int vol_control_parameters;      ///< does the stream contain the low_delay flag, used to workaround buggy encoders 
+    int intra_dc_threshold;          ///< QP above whch the ac VLC should be used for intra dc 
     PutBitContext tex_pb;            ///< used for data partitioned VOPs 
     PutBitContext pb2;               ///< used for data partitioned VOPs 
 #define PB_BUFFER_SIZE 1024*256