Add WSS (Wide Screen Signaling) Support For ld-process-vbi & ld-chroma-encoder

[harrypm]

Was just reading over a couple of things and noticed issue #677 which support was not implemented for WSS, so I am making this issue to add WSS support.

This would be incredibly useful on the tape side not only to set flags properly for video rendering via gen_chroma_vid.sh scripts, but also as some tapes are recorded in the cropped letterbox format.

Most fully equipped colour bar generators can flag 16:9/4:3 like ones found in HDV cameras with Composite/S-Video out for legacy use, also this is possible with the HackTV, but this implementation mostly applies to 16:9 anamorphic or squeezed output found in broadcast airings and some release media.

Implimentation

• Add reading support to ld-process-vbi
• Add writing support to ld-chroma-encoder

Sample Data Permalink

Sample data from CVBS-Decode (Via HVR-Z5E PAL) 16:9 Anamorphic (Squeeze) / 4:3 Edge Crop / 16:9 Letterbox

WSS Basic Flags

• full format 4:3

• full format 16:9 (anamorphic)

• letterbox

• pillar-box

• zoomed letterbox

WSS Full Flags

Raster Example

16:9 Example

Technical

Line 23 is its standard position typically observed.

EN 300 294 V1.3.2 (1998-04)

Rec. ITU-R BT.1119-2 (1994-1995-1998)

[ifb]

What do you mean by "Add writing support to ld-chroma-encoder"? The only way it has to signal any sort of metadata (PAR or otherwise) is when you use y4m. That code is already there.

[harrypm]

@ifb I mean literally generating based on the file or by manual flags, then embedding WSS lines into line 23 or higher.

It's a small thing but a relatively large upgrade for test media generation, and correct metadata flagging.

[ifb]

Oh, I read that (several times) as ld-chroma-decoder.

WSS reading isn't too far different from closed captions. @atsampson might be interested in adding it. XDS (in closed captions) can signal aspect ratio too, but I don't think that was ever widely used. V-chip and time of day (for automatically setting VCR time) was its main use case.

Writing WSS is pretty obscure. Maybe someone will work on it. Personally, I'd want to add an SCC writer but that'd be more involved.

[harrypm]

Well, it's a simple repeating pattern to replicate for anamorphic 16:9 (we have sample data on the drive) also we have a software VITC generator thanks to Unai VITC so integrating that at some point in future would be helpful.

[DreckSoft]

It the WSS used anywhere besides PALplus?

So this could be a start for #555

[harrypm]

@DreckSoft Mostly tape media releases, and pretty normal in 2000s era TV recordings, and most HD/HDV era camcorders have WSS on their outputs for composite.