* Adds some missing methods signatures.
* integer vs float framerate is a longstanging debate. In theory,
in digital a/v there should not be need for floating point framerates.
This is because unless the software is run on exoteric hardware, there
is not need for it. Unfortunately, some legacy from the past like the
29.7 hz debate (NTSC) still may need to work under floating point framerates.
Even if in pratice it'd be run at 30 hz anyway.
* In theory, to handle all those correctly we should use a rational framerate,
however most code should be rewritten to support that correctly, and
it'd add some excessive complexities.
* All integer types are reverted back to unsigned ones. There's really
no reason to use signed integers there, and more importantly the danger
for integer underflows and the attached security concerns is very big.
* We try to conform to what ffmpeg does, it is
unuseful to support metadata keys formats which
aren't really used anywhere.
* Add TODO with some infos for future improvements.
* Use string keys. I am still convinced we need BValue.
* Use boolean instead of status_t in return, this is
much more handy in pratical use given that there's no
really a status to check.
