[FFmpeg-devel] [PATCH] avcodec/vp9_parser: parse size and colorspace values from frame headers

[Michael Niedermayer]

On Fri, Jan 19, 2018 at 12:51:21AM -0300, James Almer wrote:
> Improves remuxing support when vp9 decoder is not compiled in.
> 
> Signed-off-by: James Almer <jamrial at gmail.com>
> ---
>  libavcodec/vp9_parser.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 97 insertions(+), 1 deletion(-)
> 
> diff --git a/libavcodec/vp9_parser.c b/libavcodec/vp9_parser.c
> index 9531f34a32..b059477747 100644
> --- a/libavcodec/vp9_parser.c
> +++ b/libavcodec/vp9_parser.c
> @@ -23,15 +23,69 @@
>  
>  #include "libavutil/intreadwrite.h"
>  #include "libavcodec/get_bits.h"
> +#include "libavcodec/internal.h"
>  #include "parser.h"
>  
> +#define VP9_SYNCCODE 0x498342
> +
> +static int read_colorspace_details(AVCodecParserContext *ctx, AVCodecContext *avctx,
> +                                   GetBitContext *gb)
> +{
> +    static const enum AVColorSpace colorspaces[8] = {
> +        AVCOL_SPC_UNSPECIFIED, AVCOL_SPC_BT470BG, AVCOL_SPC_BT709, AVCOL_SPC_SMPTE170M,
> +        AVCOL_SPC_SMPTE240M, AVCOL_SPC_BT2020_NCL, AVCOL_SPC_RESERVED, AVCOL_SPC_RGB,
> +    };
> +    int bits = avctx->profile <= 1 ? 0 : 1 + get_bits1(gb); // 0:8, 1:10, 2:12
> +
> +    avctx->colorspace = colorspaces[get_bits(gb, 3)];
> +    if (avctx->colorspace == AVCOL_SPC_RGB) { // RGB = profile 1
> +        static const enum AVPixelFormat pix_fmt_rgb[3] = {
> +            AV_PIX_FMT_GBRP, AV_PIX_FMT_GBRP10, AV_PIX_FMT_GBRP12
> +        };
> +        if (avctx->profile & 1) {
> +            if (get_bits1(gb)) // reserved bit
> +                return AVERROR_INVALIDDATA;
> +        } else
> +            return AVERROR_INVALIDDATA;
> +        avctx->color_range = AVCOL_RANGE_JPEG;
> +        ctx->format = pix_fmt_rgb[bits];
> +    } else {
> +        static const enum AVPixelFormat pix_fmt_for_ss[3][2 /* v */][2 /* h */] = {
> +            { { AV_PIX_FMT_YUV444P,   AV_PIX_FMT_YUV422P },
> +              { AV_PIX_FMT_YUV440P,   AV_PIX_FMT_YUV420P } },
> +            { { AV_PIX_FMT_YUV444P10, AV_PIX_FMT_YUV422P10 },
> +              { AV_PIX_FMT_YUV440P10, AV_PIX_FMT_YUV420P10 } },
> +            { { AV_PIX_FMT_YUV444P12, AV_PIX_FMT_YUV422P12 },
> +              { AV_PIX_FMT_YUV440P12, AV_PIX_FMT_YUV420P12 } }
> +        };
> +        avctx->color_range = get_bits1(gb) ? AVCOL_RANGE_JPEG : AVCOL_RANGE_MPEG;
> +        if (avctx->profile & 1) {
> +            int ss_h, ss_v, format;
> +
> +            ss_h = get_bits1(gb);
> +            ss_v = get_bits1(gb);
> +            format = pix_fmt_for_ss[bits][ss_v][ss_h];
> +            if (format == AV_PIX_FMT_YUV420P)
> +                // YUV 4:2:0 not supported in profiles 1 and 3
> +                return AVERROR_INVALIDDATA;
> +            else if (get_bits1(gb)) // color details reserved bit
> +                return AVERROR_INVALIDDATA;
> +            ctx->format = format;
> +        } else {
> +            ctx->format = pix_fmt_for_ss[bits][1][1];
> +        }
> +    }
> +
> +    return 0;
> +}
> +
>  static int parse(AVCodecParserContext *ctx,
>                   AVCodecContext *avctx,
>                   const uint8_t **out_data, int *out_size,
>                   const uint8_t *data, int size)
>  {
>      GetBitContext gb;
> -    int res, profile, keyframe;
> +    int res, profile, keyframe, invisible, errorres;
>  
>      *out_data = data;
>      *out_size = size;
> @@ -42,21 +96,63 @@ static int parse(AVCodecParserContext *ctx,
>      profile  = get_bits1(&gb);
>      profile |= get_bits1(&gb) << 1;
>      if (profile == 3) profile += get_bits1(&gb);
> +    if (profile > 3)
> +        return size;
>  
>      if (get_bits1(&gb)) {
>          keyframe = 0;
> +        skip_bits(&gb, 3);
>      } else {
>          keyframe  = !get_bits1(&gb);
>      }
>  
> +    invisible = !get_bits1(&gb);
> +    errorres  = get_bits1(&gb);
> +
>      if (!keyframe) {
> +        int intraonly = invisible ? get_bits1(&gb) : 0;
> +        if (!errorres)
> +            skip_bits(&gb, 2);
> +        if (intraonly) {
> +            if (get_bits_long(&gb, 24) != VP9_SYNCCODE) // synccode
> +                return size;
> +            avctx->profile = profile;
> +            if (profile >= 1) {
> +                if ((read_colorspace_details(ctx, avctx, &gb)) < 0)
> +                    return size;
> +            } else {
> +                ctx->format        = AV_PIX_FMT_YUV420P;
> +                avctx->colorspace  = AVCOL_SPC_BT470BG;
> +                avctx->color_range = AVCOL_RANGE_MPEG;
> +            }
> +            skip_bits(&gb, 8); // refreshrefmask
> +            ctx->width  = get_bits(&gb, 16) + 1;
> +            ctx->height = get_bits(&gb, 16) + 1;
> +            if (get_bits1(&gb)) // display size
> +                skip_bits(&gb, 32);
> +        }
> +
>          ctx->pict_type = AV_PICTURE_TYPE_P;
>          ctx->key_frame = 0;
>      } else {
> +        if (get_bits_long(&gb, 24) != VP9_SYNCCODE) // synccode
> +            return size;
> +        avctx->profile = profile;
> +        if (read_colorspace_details(ctx, avctx, &gb) < 0)
> +            return size;
> +        ctx->width  = get_bits(&gb, 16) + 1;
> +        ctx->height = get_bits(&gb, 16) + 1;
> +        if (get_bits1(&gb)) // display size
> +            skip_bits(&gb, 32);
> +
>          ctx->pict_type = AV_PICTURE_TYPE_I;
>          ctx->key_frame = 1;
>      }
>  

> +    if (ctx->width && (!avctx->width || !avctx->height ||
> +                       !avctx->coded_width || !avctx->coded_height))
> +        ff_set_dimensions(avctx, ctx->width, ctx->height);

This is the only ff_set_dimensions() in the codebase with non fixed parameters
that ignores the return value 
is that intended ?

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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