From: "Tomas Härdin" <git@haerdin.se>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH] avcodec/libjxlenc: support negative linesizes
Date: Tue, 30 Jan 2024 10:34:38 +0100
Message-ID: <9e18e68062ba0a3989d7b77a6e68508607764f1e.camel@haerdin.se> (raw)
In-Reply-To: <20240130003750.27503-1-leo.izen@gmail.com>
mån 2024-01-29 klockan 19:37 -0500 skrev Leo Izen:
> libjxl doesn't support negative strides, but JPEG XL has an
> orientation
> flag inside the codestream. We can use this to work around the
> library
> limitation, by taking the absolute value of the negative row stride,
> sending the image up-side-down, and telling the library that the
> image
> has a vertical-flip orientation.
Coincidentally we were just talking about negative stride on IRC
yesterday.
> jxl_fmt.endianness = JXL_NATIVE_ENDIAN;
> - jxl_fmt.align = frame->linesize[0];
> + if (frame->linesize[0] >= 0) {
> + jxl_fmt.align = frame->linesize[0];
> + data = frame->data[0];
> + } else {
> + jxl_fmt.align = -frame->linesize[0];
> + data = frame->data[0] - jxl_fmt.align * (info.ysize - 1);
Looks correct
/Tomas
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next prev parent reply other threads:[~2024-01-30 9:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-30 0:37 Leo Izen
2024-01-30 9:34 ` Tomas Härdin [this message]
2024-01-30 9:39 ` Andreas Rheinhardt
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