[FFmpeg-devel] [PATCH] avdevice/decklink_dec: Extract NTSC VANC
cus at passwd.hu
Mon Feb 5 21:04:00 EET 2018
On Mon, 5 Feb 2018, Devin Heitmueller wrote:
> 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.
Have you found which standard contains reference to interleaved VANC?
> 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.
I think the plan was to check if the mode is NTSC _and_ the first VANC
header is present in an interleaved way. So the HD modes would remain as
I only found ITU-R BT.1364-3 which states that luma and chroma are
separate VANC spaces, so that is why I thought autodetection for even
NTSC would make it more compatible with newer equipment respecting this
If you think this is unnecesary then so be it, I have no experience with
real life baseband NTSC signals.
More information about the ffmpeg-devel