[FFmpeg-devel] [PATCH 1/2] libopenjpegdec: set max_lowres to UINT8_MAX

[Michael Niedermayer]

On Wed, Jul 18, 2012 at 09:51:44PM -0600, Michael Bradshaw wrote:
> Paul pointed out that OpenJPEG doesn't have a max lowres limit. See
> http://ffmpeg.org/pipermail/ffmpeg-devel/2012-July/127906.html
> 
> This removes the arbitrary limit.
> 
> Thanks,
> 
> Michael

>  libopenjpegdec.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> bc2d62e1146b20a9da2d5cd1e86884081e7c0cd8  0001-libopenjpegdec-set-max_lowres-to-UINT8_MAX.patch
> From 643d6db4faf35b57b8d834d4dd1db90165ad257f Mon Sep 17 00:00:00 2001
> From: Michael Bradshaw <mbradshaw at sorensonmedia.com>
> Date: Wed, 18 Jul 2012 21:47:33 -0600
> Subject: [PATCH 1/2] libopenjpegdec: set max_lowres to UINT8_MAX
> 
> OpenJPEG doesn't have a max limit, so don't enforce an arbitrary one.
> 
> Signed-off-by: Michael Bradshaw <mbradshaw at sorensonmedia.com>
> ---
>  libavcodec/libopenjpegdec.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/libavcodec/libopenjpegdec.c b/libavcodec/libopenjpegdec.c
> index 5b5d27b..31fff7c 100644
> --- a/libavcodec/libopenjpegdec.c
> +++ b/libavcodec/libopenjpegdec.c
> @@ -388,7 +388,7 @@ AVCodec ff_libopenjpeg_decoder = {
>      .close            = libopenjpeg_decode_close,
>      .decode           = libopenjpeg_decode_frame,
>      .capabilities     = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,
> -    .max_lowres       = 5,
> +    .max_lowres       = UINT8_MAX,

this is possibly problematic

lowres is in log2 units, a value of 255 would dwarf the act of
reducing a image the size of teh vissible universe with pixels as
small as subatomic particles down to a single pixel.
that alone wouldnt be a problem but a more realworld issue
is that lowres is used in the form of width >> lowres and shifts
become undefined when they exceed the number of bits of the shifted
field, thus i would suggest that the largest limit would be 31 or
possibly less. 31 still would allow 2147483648x2147483648 to be
decoded as 1x1.


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
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