[FFmpeg-devel] [PATCH] avdevice/decklink_dec: Extract NTSC VANC

Devin Heitmueller dheitmueller at ltnglobal.com
Mon Feb 5 20:23:55 EET 2018

Hello Marton,

> I thought you are working on an updated patch, or I just missed the new one? The email you replied to here definitely contains the old, without interleaved VANC autodetection or proper width for get_metadata.

I did some digging into this after discussion with Ray (both by reviewing the SMPTE specs as well as doing some testing here with my Sencore MRD4400 decoder).  The use of VANC over both luma and chroma is because it’s an SD format. Hence it will only be present in specific modes.  When doing HD formats, the VANC packets will be exclusively found in the luma region.

That said, the list of modes should probably be expanded to include all the SD resolutions (although you’re unlikely to see CEA-708 over non-NTSC streams).  However I don’t think it would be a good idea to attempt to ‘autodetect” by applying both algorithms over all VANC lines regardless of mode.

As a result of these findings I’ll also be making a tweak to libklvanc, adding an entry point to the library which simply takes the entire V210 line, and the library can apply the appropriate colorspace conversions internally (hence eliminating the need for this sort of decision making to occur in the application).


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