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Re: [Qemu-devel] [5076] VNC: Support for ExtendedKeyEvent client message


From: Christian Brunschen
Subject: Re: [Qemu-devel] [5076] VNC: Support for ExtendedKeyEvent client message
Date: Thu, 28 Aug 2008 21:44:54 +0100


On 28 Aug 2008, at 21:32, Anthony Liguori wrote:

Alexander Graf wrote:

On Aug 24, 2008, at 1:27 AM, Anthony Liguori wrote:

How do you standardize VNC protocol extensions? I've been wondering about this for quite a while as I've got two VNC patches in my queue myself. The first one allows the client to send a keyboard layout (so the - k option could be changed dynamically, mostly because the Java client can't find symcodes).

There's no need. Simply do the conversion from Java keysyms => PC scan code using the same conversion routines that QEMU use within your Java client.

The other one implements PNG compression for Tight.

I doubt you'll see a benefit from this. PNG compression is paletted and compressed (just like GIF).

PNG does more than that. PNG supports full colour (up to 16 bits per colour component) including a full alpha channel, and has various filters that are applied to the image data to improve compression. Not to mention PNG is much more than GIF.

Tight already supports paletting and compression (using zlib). Algorithmically, you're not going to get any benefit.

The PNG filters do improve compression over raw zlib compression of the pixels.

The reason tight supports jpeg compression is that jpeg is a lossy compression algorithm. This is why jpeg compression can do better than the normal Tight algorithm (although you lose quality).

As an aside - is the Tight protocol documented somewhere? In actual documentation rather than source code, I mean?

Regards,

Best wishes,

Anthony Liguori

// Christian Brunschen




I'd really love to have both of them standardized, but where do I need to apply for an identifier ID?

[...snip...]

Thanks,

Alex








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