huge vbv buffer size + CBR fix

Originally committed as revision 2929 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mpegvideo.c

@@ -885,8 +885,15 @@ int MPV_encode_init(AVCodecContext *avctx)
 
     if(avctx->rc_min_rate && avctx->rc_max_rate != avctx->rc_min_rate){
         av_log(avctx, AV_LOG_INFO, "Warning min_rate > 0 but min_rate != max_rate isnt recommanded!\n");
-    }    
+    }
+    
+    if(   s->avctx->rc_max_rate && s->avctx->rc_min_rate == s->avctx->rc_max_rate 
+       && (s->codec_id == CODEC_ID_MPEG1VIDEO || s->codec_id == CODEC_ID_MPEG2VIDEO)
+       && 90000LL * (avctx->rc_buffer_size-1) > s->avctx->rc_max_rate*0xFFFFLL){
         
+        av_log(avctx, AV_LOG_INFO, "Warning vbv_delay will be set to 0xFFFF (=VBR) as the specified vbv buffer is too large for the given bitrate!\n");
+    }
+       
     if((s->flags & CODEC_FLAG_4MV) && s->codec_id != CODEC_ID_MPEG4 
        && s->codec_id != CODEC_ID_H263 && s->codec_id != CODEC_ID_H263P && s->codec_id != CODEC_ID_FLV1){
         av_log(avctx, AV_LOG_ERROR, "4MV not supported by codec\n");
@@ -2115,7 +2122,8 @@ int MPV_encode_picture(AVCodecContext *avctx,
         }
 
         /* update mpeg1/2 vbv_delay for CBR */    
-        if(s->avctx->rc_max_rate && s->avctx->rc_min_rate == s->avctx->rc_max_rate && s->out_format == FMT_MPEG1){
+        if(s->avctx->rc_max_rate && s->avctx->rc_min_rate == s->avctx->rc_max_rate && s->out_format == FMT_MPEG1
+           && 90000LL * (avctx->rc_buffer_size-1) <= s->avctx->rc_max_rate*0xFFFFLL){
             int vbv_delay;
 
             assert(s->repeat_first_field==0);