diff --git a/ffmpeg.c b/ffmpeg.c
index 40369b8374..59e19bf205 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -1369,6 +1369,11 @@ void opt_video_bitrate_min(const char *arg)
     video_rc_min_rate = atoi(arg) * 1000;
 }
 
+void opt_video_buffer_size(const char *arg)
+{
+    video_rc_buffer_size = atoi(arg) * 1000;
+}
+
 void opt_video_rc_eq(char *arg)
 {
     video_rc_eq = arg;
@@ -1900,6 +1905,7 @@ void opt_output_file(const char *filename)
             video_enc->rc_max_rate = video_rc_max_rate;
             video_enc->rc_min_rate = video_rc_min_rate;
             video_enc->rc_buffer_size = video_rc_buffer_size;
+            video_enc->rc_buffer_aggressivity= video_rc_buffer_aggressivity;
             video_enc->i_quant_factor = video_i_qfactor;
             video_enc->b_quant_factor = video_b_qfactor;
             video_enc->i_quant_offset = video_i_qoffset;
@@ -2260,6 +2266,7 @@ const OptionDef options[] = {
     { "bt", HAS_ARG, {(void*)opt_video_bitrate_tolerance}, "set video bitrate tolerance (in kbit/s)", "tolerance" },
     { "maxrate", HAS_ARG, {(void*)opt_video_bitrate_max}, "set max video bitrate tolerance (in kbit/s)", "bitrate" },
     { "minrate", HAS_ARG, {(void*)opt_video_bitrate_min}, "set min video bitrate tolerance (in kbit/s)", "bitrate" },
+    { "bufsize", HAS_ARG, {(void*)opt_video_buffer_size}, "set ratecontrol buffere size (in kbit)", "size" },
     { "vd", HAS_ARG | OPT_EXPERT, {(void*)opt_video_device}, "set video grab device", "device" },
     { "vcodec", HAS_ARG | OPT_EXPERT, {(void*)opt_video_codec}, "force video codec", "codec" },
     { "me", HAS_ARG | OPT_EXPERT, {(void*)opt_motion_estimation}, "set motion estimation method", 
diff --git a/libavcodec/ratecontrol.c b/libavcodec/ratecontrol.c
index 77af3c93c4..252ce7f7f6 100644
--- a/libavcodec/ratecontrol.c
+++ b/libavcodec/ratecontrol.c
@@ -377,7 +377,7 @@ static double modify_qscale(MpegEncContext *s, RateControlEntry *rce, double q,
         q*= s->avctx->rc_qmod_amp;
 
     bits= qp2bits(rce, q);
-
+//printf("q:%f\n", q);
     /* buffer overflow/underflow protection */
     if(buffer_size){
         double expected_size= rcc->buffer_index - bits;
@@ -385,16 +385,18 @@ static double modify_qscale(MpegEncContext *s, RateControlEntry *rce, double q,
         if(min_rate){
             double d= 2*(buffer_size - (expected_size + min_rate))/buffer_size;
             if(d>1.0) d=1.0;
-            q/= pow(d, 1.0/s->avctx->rc_buffer_aggressivity);
+            else if(d<0.0001) d=0.0001;
+            q*= pow(d, 1.0/s->avctx->rc_buffer_aggressivity);
         }
 
         if(max_rate){
             double d= 2*expected_size/buffer_size;
             if(d>1.0) d=1.0;
-            q*= pow(d, 1.0/s->avctx->rc_buffer_aggressivity);
+            else if(d<0.0001) d=0.0001;
+            q/= pow(d, 1.0/s->avctx->rc_buffer_aggressivity);
         }
     }
-
+//printf("q:%f max:%f min:%f size:%f index:%d bits:%f agr:%f\n", q,max_rate, min_rate, buffer_size, rcc->buffer_index, bits, s->avctx->rc_buffer_aggressivity);
     if(s->avctx->rc_qsquish==0.0 || qmin==qmax){
         if     (q<qmin) q=qmin;
         else if(q>qmax) q=qmax;
@@ -460,7 +462,7 @@ int ff_rate_estimate_qscale(MpegEncContext *s)
     get_qminmax(&qmin, &qmax, s, pict_type);
 
     fps= (double)s->frame_rate / FRAME_RATE_BASE;
-//printf("input_picture_number:%d picture_number:%d\n", s->input_picture_number, s->picture_number);
+//printf("input_pic_num:%d pic_num:%d frame_rate:%d\n", s->input_picture_number, s->picture_number, s->frame_rate);
         /* update predictors */
     if(picture_number>2){
         const int last_var= s->last_pict_type == I_TYPE ? rcc->last_mb_var_sum : rcc->last_mc_mb_var_sum;
@@ -544,6 +546,8 @@ int ff_rate_estimate_qscale(MpegEncContext *s)
             q= short_term_q= rcc->short_term_qsum/rcc->short_term_qcount;
 //printf("%f ", q);
         }
+        assert(q>0.0);
+        
         q= modify_qscale(s, rce, q, picture_number);
 
         rcc->pass1_wanted_bits+= s->bit_rate/fps;
@@ -566,8 +570,8 @@ int ff_rate_estimate_qscale(MpegEncContext *s)
     qscale= (int)(q + 0.5);
 //printf("%d ", qscale);
     
-//printf("q:%d diff:%d comp:%f rate_q:%d st_q:%f fvar:%d last_size:%d\n", qscale, (int)diff, br_compensation, 
-//       rate_q, short_term_q, s->mc_mb_var, s->frame_bits);
+//printf("q:%d diff:%d comp:%f st_q:%f last_size:%d\n", qscale, (int)diff, br_compensation, 
+//       short_term_q, s->frame_bits);
 //printf("%d %d\n", s->bit_rate, (int)fps);
 
     rcc->last_qscale= qscale;