Manipulate frame metadata.

This filter accepts the following options:

mode

Set mode of operation of the filter.

Can be one of the following:

select

If both value and key is set, select frames which have such metadata. If only key is set, select every frame that has such key in metadata.

add

Add new metadata key and value. If key is already available do nothing.

modify

Modify value of already present key.

delete

If value is set, delete only keys that have such value. Otherwise, delete key. If key is not set, delete all metadata values in the frame.

print

Print key and its value if metadata was found. If key is not set print all metadata values available in frame.

key

Set key used with all modes. Must be set for all modes except print and delete.

value

Set metadata value which will be used. This option is mandatory for modify and add mode.

function

Which function to use when comparing metadata value and value.

Can be one of following:

same_str

Values are interpreted as strings, returns true if metadata value is same as value.

starts_with

Values are interpreted as strings, returns true if metadata value starts with the value option string.

less

Values are interpreted as floats, returns true if metadata value is less than value.

equal

Values are interpreted as floats, returns true if value is equal with metadata value.

greater

Values are interpreted as floats, returns true if metadata value is greater than value.

expr

Values are interpreted as floats, returns true if expression from option expr evaluates to true.

ends_with

Values are interpreted as strings, returns true if metadata value ends with the value option string.

expr

Set expression which is used when function is set to expr. The expression is evaluated through the eval API and can contain the following constants:

VALUE1, FRAMEVAL

Float representation of value from metadata key.

VALUE2, USERVAL

Float representation of value as supplied by user in value option.

file

If specified in print mode, output is written to the named file. Instead of plain filename any writable url can be specified. Filename “-” is a shorthand for standard output. If file option is not set, output is written to the log with AV_LOG_INFO loglevel.

direct

Reduces buffering in print mode when output is written to a URL set using file.