Preserve explicit VBV and report inactive call encoder state

tools/chatgui/src/live_video_encoder.cpp

@@ -325,7 +325,8 @@ bool LiveVideoEncoder::setBitrate(int bitrate) {
 #ifdef HAVE_FFMPEG
     // libx264 перечитывает эти три значения через reconfig_encoder при подаче следующего кадра.
     if (m->codec && m->name == "libx264" && m->config.profile == LiveVideoProfile::Automatic) {
-        m->codec->bit_rate = m->codec->rc_max_rate = bitrate; m->codec->rc_buffer_size = bitrate / 4; m->config.bitrate = bitrate;
+        m->codec->bit_rate = m->codec->rc_max_rate = bitrate;
+        m->codec->rc_buffer_size = m->config.vbvBits ? m->config.vbvBits : bitrate / 4; m->config.bitrate = bitrate;
         DEBUG_INFO(DEBUG_CATEGORY_VIDEO, "desktop encoder bitrate updated in place name=libx264 bitrate=%d", bitrate); return true;
     }
 #endif