[Ffmpeg-devel] [PATCH] V.Flash PTX decoder

[Michael Niedermayer]

Hi

On Sat, Apr 28, 2007 at 06:49:18PM +0200, Ivo wrote:
> Hi,
> 
> While I was reading Mike Melanson's blog, I stumbled upon this article about 
> V.Flash V.disc cartridges. I decided to give the .ptx files a try and they 
> are just RGB555 files with a 44 byte header. Turns out there are actually 
> three (and room for four) images contained in one image.
> 
> Mike's blog entry:
> http://multimedia.cx/eggs/vdisc-analysis/
> 
> The output of _114kw_pic.ptx:
> http://ivop.free.fr/ptx/114kw_pic.png
> 
> Due to the limitted number of samples, I was unable to figure out all the 
> header fields, but enough to read and display/convert the images. Looks 
> like the width and height are repeated in the header and the few other 
> non-zero bytes might refer to the colorspace or some yet unknown flags. I 
> need more samples.
> 
> I also noticed that the most significant bit of each pixel is used as a 
> mask, probably for internal use by the V.Flash console. The bit is set if 
> the pixel is part of one of the four images. It could be seen as a 1-bit 
> alpha channel.
[...]
> +    if (avctx->get_buffer(avctx, p) < 0) {
> +        av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
> +        return -1;
> +    }
> +
> +    p->pict_type = FF_I_TYPE;
> +    p->key_frame = 1;

> +    p->reference = 0;

this must be set before get_buffer() though its actually unneeded as 0 is
default, also key_frame=1 is default so that too isnt needed


> +
> +    ptr    = p->data[0];
> +    stride = p->linesize[0];

> +    Bpp    = 2;

hmm, why B instead of b?


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 189 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20070428/4707b97f/attachment.pgp>