Re: [FFmpeg-devel] [PATCH 2/3] avcodec/j2kenc: Add alpha support

[Michael Niedermayer <michael@niedermayer.cc>]

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On Fri, Mar 31, 2023 at 01:14:40AM +0200, Michael Niedermayer wrote:
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavcodec/j2kenc.c | 28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/libavcodec/j2kenc.c b/libavcodec/j2kenc.c
> index 97b0da1c976..b23fb73770a 100644
> --- a/libavcodec/j2kenc.c
> +++ b/libavcodec/j2kenc.c
> @@ -320,8 +320,8 @@ static int put_siz(Jpeg2000EncoderContext *s)
>  
>      for (i = 0; i < s->ncomponents; i++){ // Ssiz_i XRsiz_i, YRsiz_i
>          bytestream_put_byte(&s->buf, s->cbps[i] - 1);
> -        bytestream_put_byte(&s->buf, i?1<<s->chroma_shift[0]:1);
> -        bytestream_put_byte(&s->buf, i?1<<s->chroma_shift[1]:1);
> +        bytestream_put_byte(&s->buf, (i%3)?1<<s->chroma_shift[0]:1);
> +        bytestream_put_byte(&s->buf, (i%3)?1<<s->chroma_shift[1]:1);

i will replace the %3 by +1&2 to avoid slow modulo before applying


[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

You can kill me, but you cannot change the truth.

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