diff --git a/libavcodec/h263.c b/libavcodec/h263.c
index 24ba4b09ac..9175eff0ef 100644
--- a/libavcodec/h263.c
+++ b/libavcodec/h263.c
@@ -5418,6 +5418,8 @@ static int decode_vol_header(MpegEncContext *s, GetBitContext *gb){
     if (get_bits1(gb) != 0) {   /* fixed_vop_rate  */
         skip_bits(gb, s->time_increment_bits);
     }
+    
+    s->t_frame=0;
 
     if (s->shape != BIN_ONLY_SHAPE) {
         if (s->shape == RECT_SHAPE) {
@@ -5691,7 +5693,7 @@ static int decode_vop_header(MpegEncContext *s, GetBitContext *gb){
     else time_increment= get_bits(gb, s->time_increment_bits);
     
 //    printf("%d %X\n", s->time_increment_bits, time_increment);
-//printf(" type:%d modulo_time_base:%d increment:%d\n", s->pict_type, time_incr, time_increment);
+//av_log(s->avctx, AV_LOG_DEBUG, " type:%d modulo_time_base:%d increment:%d t_frame %d\n", s->pict_type, time_incr, time_increment, s->t_frame);
     if(s->pict_type!=B_TYPE){
         s->last_time_base= s->time_base;
         s->time_base+= time_incr;
@@ -5713,19 +5715,19 @@ static int decode_vop_header(MpegEncContext *s, GetBitContext *gb){
             return FRAME_SKIPED;
         }
         
-        if(s->t_frame==0) s->t_frame= s->time - s->last_time_base;
+        if(s->t_frame==0) s->t_frame= s->pb_time;
         if(s->t_frame==0) s->t_frame=1; // 1/0 protection
-//printf("%Ld %Ld %d %d\n", s->last_non_b_time, s->time, s->pp_time, s->t_frame); fflush(stdout);
         s->pp_field_time= (  ROUNDED_DIV(s->last_non_b_time, s->t_frame) 
                            - ROUNDED_DIV(s->last_non_b_time - s->pp_time, s->t_frame))*2;
         s->pb_field_time= (  ROUNDED_DIV(s->time, s->t_frame) 
                            - ROUNDED_DIV(s->last_non_b_time - s->pp_time, s->t_frame))*2;
     }
+//av_log(s->avctx, AV_LOG_DEBUG, "last nonb %Ld last_base %d time %Ld pp %d pb %d t %d ppf %d pbf %d\n", s->last_non_b_time, s->last_time_base, s->time, s->pp_time, s->pb_time, s->t_frame, s->pp_field_time, s->pb_field_time);
     
     s->current_picture_ptr->pts= s->time*(int64_t)AV_TIME_BASE / s->time_increment_resolution;
     if(s->avctx->debug&FF_DEBUG_PTS)
         av_log(s->avctx, AV_LOG_DEBUG, "MPEG4 PTS: %f\n", s->current_picture_ptr->pts/(float)AV_TIME_BASE);
-    
+
     check_marker(gb, "before vop_coded");
     
     /* vop coded */