[FFmpeg-devel] [PATCH 2/2] avformat/img2dec: add GEM Raster image demuxer

[Andreas Rheinhardt]

On Fri, Sep 17, 2021 at 10:39 AM Peter Ross <pross at xvid.org> wrote:
>
> ---
>  libavformat/allformats.c |  1 +
>  libavformat/img2.c       |  3 +++
>  libavformat/img2dec.c    | 22 ++++++++++++++++++++++
>  3 files changed, 26 insertions(+)
>
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index 5471f7c16f..99d8c91e00 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -499,6 +499,7 @@ extern const AVInputFormat  ff_image_cri_pipe_demuxer;
>  extern const AVInputFormat  ff_image_dds_pipe_demuxer;
>  extern const AVInputFormat  ff_image_dpx_pipe_demuxer;
>  extern const AVInputFormat  ff_image_exr_pipe_demuxer;
> +extern const AVInputFormat  ff_image_gem_pipe_demuxer;
>  extern const AVInputFormat  ff_image_gif_pipe_demuxer;
>  extern const AVInputFormat  ff_image_j2k_pipe_demuxer;
>  extern const AVInputFormat  ff_image_jpeg_pipe_demuxer;
> diff --git a/libavformat/img2.c b/libavformat/img2.c
> index 6bdd7efe26..4153102c92 100644
> --- a/libavformat/img2.c
> +++ b/libavformat/img2.c
> @@ -84,6 +84,9 @@ const IdStrMap ff_img_tags[] = {
>      { AV_CODEC_ID_XPM,        "xpm"      },
>      { AV_CODEC_ID_XFACE,      "xface"    },
>      { AV_CODEC_ID_XWD,        "xwd"      },
> +    { AV_CODEC_ID_GEM,        "img"      },
> +    { AV_CODEC_ID_GEM,        "ximg"     },
> +    { AV_CODEC_ID_GEM,        "timg"     },
>      { AV_CODEC_ID_NONE,       NULL       }
>  };
>
> diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
> index 485444ed31..acfd5910de 100644
> --- a/libavformat/img2dec.c
> +++ b/libavformat/img2dec.c
> @@ -1105,6 +1105,27 @@ static int photocd_probe(const AVProbeData *p)
>      return AVPROBE_SCORE_MAX - 1;
>  }
>
> +static int gem_probe(const AVProbeData *p)
> +{
> +    const uint8_t *b = p->buf;
> +    int ret = 0;
> +    if ( AV_RB16(b     ) >= 1 && AV_RB16(b    ) <= 3  &&
> +         AV_RB16(b +  2) >= 8 && AV_RB16(b + 2) <= 779 &&
> +        (AV_RB16(b +  4) > 0  || AV_RB16(b + 4) <= 8) &&
> +        (AV_RB16(b +  6) > 0  || AV_RB16(b + 6) <= 8) &&

The above two lines are tautologically true, suggesting that something
else was intended here.
Looking at the decoder shows that this is the aspect ratio, so
checking for them being >0 makes sense,
yet the checks for them being <= 8 doesn't.
(This has been reported in ticket #9605.)

> +         AV_RB16(b +  8) &&
> +         AV_RB16(b + 10) &&
> +         AV_RB16(b + 12) &&
> +         AV_RB16(b + 14)) {
> +        ret = AVPROBE_SCORE_EXTENSION / 4;
> +        if (AV_RN32(b + 16) == AV_RN32("STTT") ||
> +            AV_RN32(b + 16) == AV_RN32("TIMG") ||
> +            AV_RN32(b + 16) == AV_RN32("XIMG"))
> +            ret += 1;
> +    }
> +    return ret;
> +}
> +