The expanses of WolfWings' land
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March 17th, 2004
March 17th, 2004
March 17th, 2004
March 17th, 2004
March 17th, 2004

[User Picture]05:03 pm - Ya' know... some people just don't get what 'reverse engineering' really is.
Take the 'VideoNOW' players being advertised these days. Mini-CD players with a low-resolution grayscale LCD screen on top.

There's this big hullabaloo about 'reverse engineering' the file format and it being 'cracked' and 'busted wide open' after 'weeks of work' (actual quotes) that I've been noticing more recently.

And the current descriptions are stupidly complex. Insanely complicated series of operations just to extract a SINGLE FRAME of animation, let alone sound too.

Now, want to know the kicker? The 'file format', such as it is, is positively trivial. We're talking no compression, no headers, just raw frames and audio here, in a fixed format, by stripping and repurposing certain bits in the usual CD-audio data stream.

First, assume you have a 'video buffer' of 5880 bytes, and an 'audio buffer' of 2940 bytes.

Next, take 5 sectors in a row as CD-DA (Red Book) format, so you have 11760 bytes of data.

Now, do the following 2940 times:
Append the next byte to the VIDEO buffer.
Append the next byte to the VIDEO buffer.
Append the next byte to the AUDIO buffer.
Discard the next byte.

Now, the audio buffer is full of 2940 8-bit samples. It's finished.

You can ignore everything but the first 3200 bytes of the video buffer, which is filled with a bitpacked 4-bit 80x80 grayscale image.

More technically, each byte of the video buffer is two pixels. Divide by 16 for the left-hand pixel, the remainder of that division is the right-hand pixel, with 40 such bytes in a row forming an 80-pixel line, with 80 lines being used by the display, the remainder being unused by current VideoNOW discs and players.

But what blows my mind, is that anyone could possibly think this 'file format' is something to blab about having cracked. It's like saying you worked for SCO, it's just something to convert too, release the code, and be done with. It's such a trivial application (bitmap images stored in the left channel of the audio track of the CD) that I'm truly amazed anyone could try to claim 'fame' from it.

And no, I'm not saying that because I'm smart, this file format is honestly simpler to understand than a Windows .BMP file. =-.-=2 commentsLeave a comment
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