lavc: set the default rc_initial_buffer_occupancy

rc_buffer_size is not set before.

Solve the initial the rate control underflow issue reported in
bug 222.

CC: libav-stable@libav.org

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

avconv_opt.c

@@ -950,8 +950,6 @@ static OutputStream *new_video_stream(OptionsContext *o, AVFormatContext *oc)
             if (p) p++;
         }
         video_enc->rc_override_count = i;
-        if (!video_enc->rc_initial_buffer_occupancy)
-            video_enc->rc_initial_buffer_occupancy = video_enc->rc_buffer_size * 3 / 4;
         video_enc->intra_dc_precision = intra_dc_precision - 8;
 
         /* two pass mode */

libavcodec/utils.c

@@ -824,6 +824,9 @@ int attribute_align_arg avcodec_open2(AVCodecContext *avctx, const AVCodec *code
         } else if (avctx->channel_layout) {
             avctx->channels = av_get_channel_layout_nb_channels(avctx->channel_layout);
         }
+
+        if (!avctx->rc_initial_buffer_occupancy)
+            avctx->rc_initial_buffer_occupancy = avctx->rc_buffer_size * 3 / 4;
     }
 
     if (avctx->codec->init && !(avctx->active_thread_type & FF_THREAD_FRAME)) {