« Back to Knowledge Base

Understanding FFMPEG streaming logs

vMix will uses FFMPEG for streaming by default and saves log files for each streaming session in C:\ProgramData\vMix\streaming for diagnostic purposes.
This knowledge base article will cover some common messages you may encounter:

frame=   38 fps=30.0 q=0.0 size=       1665kB time=00:00:01.23 bitrate=   2315.6kbits/s

This message means the stream at this point in time is live and working correctly.

real-time buffer [vMix Video] [video input] too full or near too full

This message coincides with the Stream button turning amber/orange in vMix and can occur in the following situations:
Starting up
If a streaming provider / CDN takes longer than usual to connect, you may see this error at the start of the log file.
This message is nothing to worry about in this situation and just means vMix is waiting a bit longer than usual for the connection to be established.
Network congestion
If this error appears after the Stream button has already turned red, and the Stream button is now Amber/Orange then it usually indicates network congestion, and less likely due to the computer or graphics card not being fast enough.

av_interleaved_write_frame(): Unknown error
av_interleaved_write_frame(): Input/output error

This error means the stream has disconnected which can occur for one of the following reasons:
1. Local internet outage
2. Streaming provider internet outage
3. Streaming provider has closed the stream for some reason
4. Third party anti virus and security software

Server error: Initialization failed

This error means the streaming provider has rejected the connection, this can be due to invalid stream key, username or password, or the stream has expired.
If using a provider such as Facebook, try creating a new stream through Facebook Settings from scratch, otherwise contact the streaming provider to verify the details being used are correct.
This may also include additional information in the message such as (2: Broadcast state is bad) which means the streaming details used are no longer valid.

Failed to update header

This message is normal and is nothing to worry about. It just means that since FFMPEG is not recording to file and only streaming, it has no file to write the header to when the stream is complete.

Last Updated: Thursday, December 9, 2021 9:22:39 AM