Hi @w0nger.

Now a year later - is this still an issue? I am also looking to record 4x4K video feeds in prores, and also have great hardware for the task. I am wondering if vMix updated their FFMPEG encoder or if i am going to run into the same issue a you :) - Do you know?

Thanks !

So vMix is giving me an I/O error whenever I try to stream out. This is to YouTube, but I tried others - I originally started trying to stream with Restream and got the error.

I know this is an internal issue, so I disabled the firewall and the problem didn't go away.

Streaming through other programs (OBS, Wirecast) is not an issue, so it's definitely located in some vMix setting.

I am short of re-installing vMix, but I thought I'd come here to see if there is anyone that has an idea of what's going on.

ffmpeg started on 2024-11-20 at 09:54:45
Report written to "C:\ProgramData\vMix\streaming\streaming1 20241120-095445.log"
Command line:
"C:\\Program Files (x86)\\vMix\\streaming\\ffmpeg2.exe" -report -rtbufsize 128M -f dshow -i "video=vMix Video YV12:audio=vMix Audio" -codec:v libx264 -s:v 1920x1080 -pix_fmt:v yuv420p -threads 4 -bufsize:v 4500k -g:v 120 -preset:v veryfast -profile:v baseline -level:v 3.1 -b:v 4500k -maxrate:v 4950k -codec:a aac -b:a 128k -strict -2 -rtmp_flashver "FMLE/3.0 (compatible; vMix/27.0.0.88)" -f flv rtmp://a.rtmp.youtube.com/live2/secret-key -codec:v h264_nvenc -s:v 1280x720 -pix_fmt:v yuv420p -threads 4 -bufsize:v 2800k -g:v 120 -preset:v llhq -profile:v baseline -b:v 2800k -maxrate:v 3080k -codec:a aac -b:a 128k -strict -2 -rtmp_flashver "FMLE/3.0 (compatible; vMix/27.0.0.88)" -f flv rtmp://a.rtmp.youtube.com/live2/secret-key
ffmpeg version 3.3.git Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 4.8.1 (rev2, Built by MinGW-W64 project)
configuration: --enable-gpl --enable-version3 --enable-libx264 --enable-zlib --enable-nvenc --cpu=i686
libavutil 55. 76.100 / 55. 76.100
libavcodec 57.106.101 / 57.106.101
libavformat 57. 82.101 / 57. 82.101
libavdevice 57. 8.101 / 57. 8.101
libavfilter 6.105.100 / 6.105.100
libswscale 4. 7.103 / 4. 7.103
libswresample 2. 8.100 / 2. 8.100
libpostproc 54. 6.100 / 54. 6.100
Guessed Channel Layout for Input Stream #0.1 : stereo
Input #0, dshow, from 'video=vMix Video YV12:audio=vMix Audio':
Duration: N/A, start: 5243.235000, bitrate: 1536 kb/s
Stream #0:0: Video: rawvideo (YV12 / 0x32315659), yuv420p, 1920x1080, 60 fps, 60 tbr, 10000k tbn, 10000k tbc
Stream #0:1: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
[tcp @ 05f88640] TCP Buffer has been set to 18890752 bytes
rtmp://a.rtmp.youtube.com/live2/secret-key: I/O error

Update:

I was correct, the issues were caused by the ridiculously outdated ffmpeg libraries being used by vmix. But then again I have a feeling the vmix team is already aware of the issue and have simply chosen to keep quiet. I'm pretty annoyed to say the least and will re-consider my choice to continue using vmix in the future.

For anyone googling this problem, I solved it by download gyan's build of ffmpeg for windows, and deleting "ffmpeg2.exe" in the vmix/streaming folder, then I moved the new ffmpeg from gyan and renamed it ffmpeg2.

I can now record 8 4k prores 422 streams without my xeon breaking a sweat.