[vlc-devel] [PATCH] swscale: Fix pixel format for VLC_CODEC_RGBA

Florian Albrechtskirchinger falbrechtskirchinger at gmail.com
Fri Dec 21 00:19:09 CET 2012

On 12/20/2012 11:33 PM, Rémi Denis-Courmont wrote:
> Le vendredi 21 décembre 2012 00:02:06, Florian Albrechtskirchinger a écrit :
>> How about taking it one step at a time:
>> 1) Rename all occurrences of VLC_CODEC_RGB(8|15|16|24|32) to
>> VLC_CODEC_RGB(8|15|16|24|32)_OLD.
>> 2) Introduce mask-less VLC_CODEC_RGB(15|16|24|32),
>> VLC_CODEC_BGR(15|16|24|32).
>> 3) Gradually port the existing code over to the new codecs.
>> 4) Remove the old codecs.
> I don't see how you can do that gradually. Multiple plugins in a given
> pipeline need to agree with one another on the meaning of given formats.
> The only criterias to divide the work are:
> - the input side (before rawvideo decoder)
>    or the output side (after rawvideo decoder), and
> - the pixel size (8, 15, 16, 24, 32).
>> What about the FourCCs? Are RV24, RV32, etc. globally used or are they
>> VLC-internal? Assuming they are internal and can be renamed without
>> consequence, here's a simple idea: RGB4 = 32bit, RGB3 = 24bit, RGB2 =
>> 16bit, RGB1 = 15bit; BGR analogous.
>> RGB8 = GREY?
> No. RGB8 is 256 colours. GREY is 8-bits grey scale (a.k.a. Y8).
>> VLC_CODEC_RGBA16 should be removed.
>>   > $ grep -r VLC_CODEC_RGBA16 .
>>   > ./include/vlc_fourcc.h:#define VLC_CODEC_RGBA16
>> VLC_FOURCC('A','V','1','6')
>>   > ./modules/video_output/xcb/xvideo.c:                    return
>>   > ./src/misc/fourcc.c:    B(VLC_CODEC_RGBA16, "16 bits RGBA"),
>>   > ./src/misc/fourcc.c:        VLC_CODEC_RGBA16, 0 },
>> Does that sound doable/reasonable to you?
>> I'd be willing to complete steps 1) and 2) and start step 3) to the
>> extent I'm immediately concerned with, i.e. XCB screen capture and
>> related code paths. I might contribute more to this end in the future,
>> starting with V4L2, but I'm not promising anything.
> Inputs (demux and access_demux plugins) are relatively easy: They only have to
> be consistent with the rawvideo decoder. But even then, all inputs must agree;
> you cannot patch each of them separately.
> The difficult and/or tedious parts regard video chroma converters, the scaler,
> blending, video filters and video outputs...
> If you are *only* interested in X11 windows capture, it would be far simpler
> to define VLC_CODEC_BGRA, and convert to VLC_CODEC_RGBA in codec/rawvideo.c.
> Then you don't need to care about all the output or RGB intricacies
I was hoping I could pick one pipeline e.g. XCB screen capture to XCB 
video output. Now, XCB screen capture wouldn't work with any other 
output, so all relevant outputs would have to be updated too. That much 
I realized. I conveniently forgot about the stuff in between.
Alright then, VLC_CODEC_BGRA it is for now. Although in the long run I'm 
not *only* interested in X11 windows capture, so anything could happen.


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