Feature request: More specific transcoding options

[tkiapril]

The transcoding options present are useful, but I have suggestions to give more versatility to the features.
First, some formats such as Opus has bitrate up to 510 and are not bound to powers of 2, so max bitrate input would be better if it was a textbox rather than a combobox.
Also, there are instances when a specific format does not work on a client (flac on HTML5), and want other formats sent out raw. Currently on the transcoding configuration, only the destination format is specified and all audio format are transcoded into such. Being able to specify a original format to be transcoded is desirable, and if there is no definition for a specific format, it can maybe fallback to a definition with no original format input (if available) or sent out raw.