[FFmpeg-devel] [PATCH v3 1/3] libavcodec/jpeg2000dec: Fix codeblock decode check

[Michael Niedermayer]

On Tue, Jul 21, 2020 at 11:37:13PM +0530, gautamramk at gmail.com wrote:
> From: Gautam Ramakrishnan <gautamramk at gmail.com>
> 
> The codeblock decoder checks whether the mqc decoder
> has decoded the right number of bytes. However, this
> check does not account for the fact that the mqc encoder's
> flush routine adds 2 bytes of data which does not have to be
> read by the decoder. The check is modified to account for
> this. This patch solves issue #4827
> ---
>  libavcodec/jpeg2000dec.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
> index f5ad8402fb..5e9e97eb6a 100644
> --- a/libavcodec/jpeg2000dec.c
> +++ b/libavcodec/jpeg2000dec.c
> @@ -1753,9 +1753,9 @@ static int decode_cblk(Jpeg2000DecoderContext *s, Jpeg2000CodingStyle *codsty,
>          pass_cnt ++;
>      }
>  
> -    if (cblk->data + cblk->length - 2*(term_cnt < cblk->nb_terminations) != t1->mqc.bp) {
> +    if (cblk->data + cblk->length - 2 > t1->mqc.bp) {
>          av_log(s->avctx, AV_LOG_WARNING, "End mismatch %"PTRDIFF_SPECIFIER"\n",

This changes a equals check to a larger than check, so it removes checking
in one direction. The commit message doesnt explain this sufficiently i think

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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