Support the TBC (4fsc) CVBS/S-Video signal file format

[harrypm]

Notation to add support for the .tbc formats NTSC and PAL.

These are files are mainly genarated by the decode projects.

The file format can be genarated in software with digital image assets or video assets details are on the chroma-encoder page or from public FM RF archives of composite/colour-under tape formats and LaserDiscs linked on the wiki's.

We currently use the FL2K Method but its far from ideal.

After seeing matts tv barn video on generating broadcast complient CVBS or well as close as possible to it has got me thinking about the future of playout in hardware again, and getting tbc support implimented into hacktv seems like a good step to make it more flexible to do so.

[fsphil]

I tried creating a sample .tbc file with:

ffmpeg -i INPUT.mkv -an -vf "scale=922:576,pad=922:576:0:3" -vcodec rawvideo -pix_fmt yuv444p16 -f rawvideo - | ld-chroma-encoder -p yuv -f PAL - OUTPUT.tbc

This produces a file with 1135 samples per line, but it doesn't seem to show the expected shift each line due to the 0.0064 rounding error. Is that expected?

[Update: Added a quick visual]

ld-chroma-encoder:

And hacktv (manually added the padding):

[harrypm]

I believe that is expected, I'm not 100% sure off the top of my head though would have to confirm with @happycube.