On Fri, 22 Apr 2016 23:06:37 +0300
Jan Ekström <jee...@gmail.com> wrote:
> Functionality used before didn't widen the values from limited to
> full range. Additionally, now the decoder uses BT.709 where it
> should be used according to the video resolution.
>
> Default for not yet set colorimetry is BT.709 due to most observed
> HDMV content being HD.
>
> BT.709 coefficients were gathered from the first two parts of BT.709
> to BT.2020 conversion guide in ARIB STD-B62 (Pt. 1, Chapter 6.2.2).
>
> Based on a patch by Carl Eugen Hoyos.
> ---
> libavcodec/pgssubdec.c | 20 ++++++++++++++++++--
> libavutil/colorspace.h | 10 ++++++++++
> 2 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/libavcodec/pgssubdec.c b/libavcodec/pgssubdec.c
> index 07a2a78..4145f1c 100644
> --- a/libavcodec/pgssubdec.c
> +++ b/libavcodec/pgssubdec.c
> @@ -96,6 +96,7 @@ typedef struct PGSSubContext {
> PGSSubPalettes palettes;
> PGSSubObjects objects;
> int forced_subs_only;
> + int hdtv;
> } PGSSubContext;
>
> static void flush_cache(AVCodecContext *avctx)
> @@ -136,6 +137,9 @@ static PGSSubPalette * find_palette(int id,
> PGSSubPalettes *palettes)
>
> static av_cold int init_decoder(AVCodecContext *avctx)
> {
> + PGSSubContext *ctx = avctx->priv_data;
> + ctx->hdtv = -1;
> +
> avctx->pix_fmt = AV_PIX_FMT_PAL8;
>
> return 0;
> @@ -354,8 +358,14 @@ static int parse_palette_segment(AVCodecContext *avctx,
> cb = bytestream_get_byte(&buf);
> alpha = bytestream_get_byte(&buf);
>
> - YUV_TO_RGB1(cb, cr);
> - YUV_TO_RGB2(r, g, b, y);
> + /* Default to HDTV (-1 or 1) */
> + if (ctx->hdtv) {
> + YUV_TO_RGB1_CCIR_BT709(cb, cr);
> + } else {
> + YUV_TO_RGB1_CCIR(cb, cr);
> + }
> +
> + YUV_TO_RGB2_CCIR(r, g, b, y);
>
> ff_dlog(avctx, "Color %d := (%d,%d,%d,%d)\n", color_id, r, g, b,
> alpha);
>
> @@ -388,6 +398,12 @@ static int parse_presentation_segment(AVCodecContext
> *avctx,
> int w = bytestream_get_be16(&buf);
> int h = bytestream_get_be16(&buf);
>
> + // Set colorimetry according to resolution
> + if (h > 576)
> + ctx->hdtv = 1;
> + else
> + ctx->hdtv = 0;
> +
> ctx->presentation.pts = pts;
>
> ff_dlog(avctx, "Video Dimensions %dx%d\n",
> diff --git a/libavutil/colorspace.h b/libavutil/colorspace.h
> index 826ffd5..7d3f711 100644
> --- a/libavutil/colorspace.h
> +++ b/libavutil/colorspace.h
> @@ -41,6 +41,16 @@
> b_add = FIX(1.77200*255.0/224.0) * cb + ONE_HALF;\
> }
>
> +#define YUV_TO_RGB1_CCIR_BT709(cb1, cr1)\
> +{\
> + cb = (cb1) - 128;\
> + cr = (cr1) - 128;\
> + r_add = FIX(1.5747*255.0/224.0) * cr + ONE_HALF;\
> + g_add = - FIX(0.1873*255.0/224.0) * cb - FIX(0.4682*255.0/224.0) * cr + \
> + ONE_HALF;\
> + b_add = FIX(1.8556*255.0/224.0) * cb + ONE_HALF;\
> +}
> +
> #define YUV_TO_RGB2_CCIR(r, g, b, y1)\
> {\
> y = ((y1) - 16) * FIX(255.0/219.0);\
This still has the problem that the palette could be read before the
resolution is known.
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