Sets the audio decoder tags and how they should be merged with any upstream stream tags.
This will override any tags previously-set with merge_tags.
Note that this is provided for convenience, and the subclass is not required to use this and can still do tag handling on its own.
| this |
a Decoder |
| tags |
a TagList to merge, or NULL |
| mode |
the TagMergeMode to use, usually REPLACE |