When playing a video with dynamic metadata, METERING is not created, so the variable does not exist. however, due to the BIND, these passes will not execute even if the WHEN condition evaluates to true. I think should first determine whether the BIND condition holds, and then evaluate the WHEN condition.
natural-harmonia-gropius/hdr-toys@5bcc2bc
//!WHEN METERING.w 1024 > throw an exception:

When playing a video with dynamic metadata, METERING is not created, so the variable does not exist. however, due to the BIND, these passes will not execute even if the WHEN condition evaluates to true. I think should first determine whether the BIND condition holds, and then evaluate the WHEN condition.
natural-harmonia-gropius/hdr-toys@5bcc2bc
//!WHEN METERING.w 1024 >throw an exception: