FFmpeg error message when converting MKV to MP4

[BigPhil1]

When using the command line:

ffmpeg -i input.mkv -vcodec copy -acodec copy output.mp4

I receive the following message:

'Using AVStream.codec to pass codec parameters to muxers is deprecated, use ASTream.codecpar instead'

The resulting file seems ok when I play it but was just wondering if anyone knows what this message means?

Thank you

[JVRaines]

Looks like a warning message prompted by an internal component that's using a deprecated method. Of course, the message is most apropos to the component developer, not to us poor end users. FFmpeg can be clunky that way. I wouldn't worry about it if you're getting good output.