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

[Marton Balint]

On Mon, 5 Feb 2018, Ray Tiley wrote:

> This changes how NTSC VANC is extracted from the buffer. In NTSC the vanc
> data interleved between the uyvy and not just the luma as in
> high definition resolutions.
>
> In my testing this allows a decklink card encoding valid NTSC closed
> captions to pass the caption data to the x264 encoder.
>
> Updated with rewviews from Devon Heitmueller and Marton Balint.
>
> Signed-off-by: Ray Tiley <raytiley at gmail.com>
> ---
> libavdevice/decklink_dec.cpp | 37 ++++++++++++++++++++++++++++++++++---
> 1 file changed, 34 insertions(+), 3 deletions(-)
>
> diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
> index 94dae26..c3683bb 100644
> --- a/libavdevice/decklink_dec.cpp
> +++ b/libavdevice/decklink_dec.cpp
> @@ -149,6 +149,30 @@ static void extract_luma_from_v210(uint16_t *dst, const uint8_t *src, int width)
>     }
> }
> 
> +static void unpack_v210(uint16_t *dst, const uint8_t *src, int width)
> +{
> +    int i;
> +    for (i = 0; i < width / 6; i++) {
> +        *dst++ =  src[0]       + ((src[1] & 3)  << 8);
> +        *dst++ = (src[1] >> 2) + ((src[2] & 15) << 6);
> +        *dst++ = (src[2] >> 4) + ((src[3] & 63) << 4);
> +
> +        *dst++ =  src[4]       + ((src[5] & 3)  << 8);
> +        *dst++ = (src[5] >> 2) + ((src[6] & 15) << 6);
> +        *dst++ = (src[6] >> 4) + ((src[7] & 63) << 4);
> +
> +        *dst++ =  src[8]       + ((src[9] & 3)  << 8);
> +        *dst++ = (src[9] >> 2) + ((src[10] & 15) << 6);
> +        *dst++ = (src[10] >> 4) + ((src[11] & 63) << 4);
> +
> +        *dst++ =  src[12]       + ((src[13] & 3)  << 8);
> +        *dst++ = (src[13] >> 2) + ((src[14] & 15) << 6);
> +        *dst++ = (src[14] >> 4) + ((src[15] & 63) << 4);
> +
> +        src += 16;
> +    }
> +}

Sorry for the delay, and for not spotting this earlier, but I think you 
can simply write this:

     int i;
     for (i = 0; i < width * 2 / 3; i++) {
         *dst++ =  src[0]       + ((src[1] & 3)  << 8);
         *dst++ = (src[1] >> 2) + ((src[2] & 15) << 6);
         *dst++ = (src[2] >> 4) + ((src[3] & 63) << 4);
         src += 4;
     }

> +
> static uint8_t calc_parity_and_line_offset(int line)
> {
>     uint8_t ret = (line < 313) << 5;
> @@ -740,9 +764,16 @@ HRESULT decklink_input_callback::VideoInputFrameArrived(
>                     for (i = vanc_line_numbers[idx].vanc_start; i <= vanc_line_numbers[idx].vanc_end; i++) {
>                         uint8_t *buf;
>                         if (vanc->GetBufferForVerticalBlankingLine(i, (void**)&buf) == S_OK) {
> -                            uint16_t luma_vanc[MAX_WIDTH_VANC];
> -                            extract_luma_from_v210(luma_vanc, buf, videoFrame->GetWidth());
> -                            txt_buf = get_metadata(avctx, luma_vanc, videoFrame->GetWidth(),
> +                            uint16_t vanc[MAX_WIDTH_VANC];
> +                            size_t vanc_size = videoFrame->GetWidth();
> +                            if (ctx->bmd_mode == bmdModeNTSC &&
> +                                videoFrame->GetWidth() * 2 <= MAX_WIDTH_VANC) {
> +                              vanc_size = vanc_size * 2;
> +                              unpack_v210(vanc, buf, videoFrame->GetWidth());

Please use 4 space indent.

> +                            } else {
> +                              extract_luma_from_v210(vanc, buf, videoFrame->GetWidth());
> +                            }
> +                            txt_buf = get_metadata(avctx, vanc, vanc_size,
>                                                    txt_buf, sizeof(txt_buf0) - (txt_buf - txt_buf0), &pkt);
>                         }
>                         if (i == vanc_line_numbers[idx].field0_vanc_end)

Thanks,
Marton