s12m timecodes

[JDarnley]

Supersedes #530

Comments very much welcome

[kierank]

I'm not sure what I think about storing them in a uref as BCD. I see why you did it but it's a bit ugly. But then again anything else would add complexity.

[nto]

Perhaps the functions in uref_attr_s12m.h should validate their input values and return UBASE_ERR_INVALID when out of range?

[JDarnley]

I added that, well something that a user can choose to use if they don't trust the data. I assume you wanted the check in the to/from functions and for those to return an error code rather than the timecode pack itself.

I wonder if I should change the check function to return false if the count is 0. Is something, someone going to add a 4 byte attribute just to hold one 0?

I also needed a function to set a flag in a different position for NTSC and PAL so that got created.

[JDarnley]

I can't get timecodes out of upipe_blackmagic_sink with any of the equipment I have available. I'm not sure why. The driver might be too old or there could be a problem with the C++ code. I'll investigate some more in the future.