volume=replaygain=track requires a + sign in front of positive values, but this is not standard replaygain spec

[simcc]

Summary of the bug:
The RGv2 specification clearly mentions the format of the tags, and it should not contain a '+' char. Try any files with replay_track_gain tags with positive values, i.e. 9.70 will not work, but if you adjust the metadata manually to +9.70, then it does work.
How to reproduce:

% ffmpeg -i input.m4a -af volume=replaygain=track output.m4a 

ffmpeg -i input.mp4 -c:v copy -af volume=replaygain=track output.mp4

etc.

ffmpeg version 4.4
built on OSX w/ homebrew

Obviously the input file will need to have replay_track_gain tags with positive values for the bug to appear, i.e. nothing happens...it works as expected with negative values.