Fix Live Stream vcodec copy on Raspberry Pi3b (maybe also for Pi2 etc)

Hello,

I've had the issue with vcodec copy option for a long time - Live stream was always failing after 1 second. Not it's fixed (config for Xiaomi Xiaofang 1S):

{
               "name":"Camera",
               "videoConfig":{
                 "source": "-rtsp_transport tcp -re -i rtsp://your_ip_address
                 "maxFPS":30,
                 "maxWidth": 1280,
                 "maxHeight": 720,
                 "videoFilter":"none",
                 "maxBitrate":1024,
                 "packetSize": 188,
                 "maxStreams":2,
                 "vcodec":"copy",
                 "audio":false
               }

Tested on ffmpeg version 4.1.4 (built with gcc 8.3.0 (Alpine 8.3.0) configuration: --prefix=/usr --enable-avresample --enable-avfilter --enable-gnutls --enable-gpl --enable-libass --enable-libmp3lame --enable-libvorbis --enable-libvpx --enable-libxvid --enable-libx264 --enable-libx265 --enable-libtheora --enable-libv4l2 --enable-postproc --enable-pic --enable-pthreads --enable-shared --enable-libxcb --disable-stripping --disable-static --disable-librtmp --enable-vaapi --enable-vdpau --enable-libopus --disable-asm --disable-debug libavutil 56. 22.100 / 56. 22.100 libavcodec 58. 35.100 / 58. 35.100 libavformat 58. 20.100 / 58. 20.100 libavdevice 58. 5.100 / 58. 5.100 libavfilter 7. 40.101 / 7. 40.101 libavresample 4. 0. 0 / 4. 0. 0 libswscale 5. 3.100 / 5. 3.100 libswresample 3. 3.100 / 3. 3.100 libpostproc 55. 3.100 / 55. 3.100