[FFmpeg-devel] [PATCH] avdevice/decklink_dec: Extract 1080i and NTSC VANC

[Ray Tiley]

On Sun, Jan 28, 2018 at 4:54 PM Marton Balint <cus at passwd.hu> wrote:

>
> On Thu, 25 Jan 2018, Ray Tiley wrote:
>
> > On Tue, Jan 23, 2018 at 9:07 AM Devin Heitmueller <
> > dheitmueller at ltnglobal.com> wrote:
> >
> >> Hi Ray,
> >>
> >>> On Jan 22, 2018, at 11:20 PM, Ray Tiley <raytiley at gmail.com> wrote:
> >>>
> >>> I'm reading 334-1:2017 Sec 4
> >>> "When the ANC packets defined in this standard are carried in a high
> >>> definition signal, they shall be carried in the Y stream."
> >>>
> >>> I couldn't find anywhere in the document where it calls out standard
> >>> definition
> >>
> >> Right, so my understanding was that allowing the ability to use both
> luma
> >> and chroma was a result of having less space in the VANC to hold data,
> >> compared to HD resolutions where that is much less likely to be an
> issue.
> >> That said, I’ve never seen an implementation that actually puts it in
> the
> >> chroma.
> >>
> >>>
> >>> Conversation is here:
> >>> https://video-dev.slack.com/archives/C0XKDDH5Y/p1516141555000074 <
> >> https://video-dev.slack.com/archives/C0XKDDH5Y/p1516141555000074> with
> >>> kierank at obe.tv <mailto:kierank at obe.tv> who I believe is in the
> >> ffmpeg-devel IRC.
> >>>
> >>
> >> Ah, ok.  That’s Kieran.  He’s really knowledgable in this area,
> although I
> >> cannot see the conversation you’ve linked to as it seems that room is
> only
> >> accessible by people with email accounts from certain domains.
> >>
> >> Devin
> >> _______________________________________________
> >> ffmpeg-devel mailing list
> >> ffmpeg-devel at ffmpeg.org
> >> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> >
> > Please find updated patch attatched. I reverted the vanc lines changes
> and
> > found that all my tests worked as expected, so not sure what was wrong w/
> > my original test. The need to extract vanc from the entire line vs just
> the
> > luma in NTSC is still required.
>
> Is interleaved VANC data is always the case for SD NTSC, or it depends on
> the equipment? Maybe we should add some auto detection, and check for the
> first VANC header. E.g.
>
> if (ctx->bmd_mode == bmdModeNTSC &&
>      (*(uint32_t*)buf & 0x3ffffffff == 0x3fffffc00))
>      unpack_v210
> else
>      unpack_luma_v210
>

Sounds good to me. Will send patch shortly.


>
> Also, later on in the code, you only parse half of the decoded VANC.
> If you decode from both the luma and chroma, get_metadata should be called
> with frame width*2, no?
>

Good catch. I was testing with very small caption packets so I did not see
it cut off. Will send patch shortly.


>
> Regards,
> Marton
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