The current Testcard W is generated in software (i.e. the gratings are generated from mathematical formulae - not simply images). It it thus possible to create it at different resolutions - and modify the resolution of the gratings etc.
The HD testcard can thus be generated in a similar manner to the SD one. I believe the original still picture of the girl and clown has been scanned at high resolution.
If you dig around for Richard Russell's website there may be a bit more on it - he wrote the software I believe. (He was also instrumental in BBC Basic - and also played a key role in the best PAL decoder currently in use - TRANSFORM - used by the BBC for their archival and high-end DVD mastering)
The current Testcard W is generated in software (i.e. the gratings are generated from mathematical formulae - not simply images). It it thus possible to create it at different resolutions - and modify the resolution of the gratings etc.
The HD testcard can thus be generated in a similar manner to the SD one. I believe the original still picture of the girl and clown has been scanned at high resolution.
Surely there's a need for any HD testcard to have some sort of moving element though? It couldn't be just a diffrent resolution version of TCW
Strictly speaking, if anyone has reconstructed TCW in Flash it would be easy to up it to HD resolution simply by increasing the output size accordingly.
When TCW was designed the central image of Carole was rescanned from the original slide using the most powerful scientific scanning equipment available, so there shouldn't be a problem with HD compatibility.
That presumes the output device has stored the picture at sufficient resolution though (probably be easier/smarter to store versions sized for 576i, 720p & 1080i/p rather than dynamically scaling a bitmap, since storing it to be scaled as sharp at all three resolutions would probably take more space...)
The current Testcard W is generated in software (i.e. the gratings are generated from mathematical formulae - not simply images). It it thus possible to create it at different resolutions - and modify the resolution of the gratings etc.
The HD testcard can thus be generated in a similar manner to the SD one. I believe the original still picture of the girl and clown has been scanned at high resolution.
Surely there's a need for any HD testcard to have some sort of moving element though? It couldn't be just a diffrent resolution version of TCW
It depends what you need the testcard to do - a static card still has uses for display line-up, but a moving element is useful for confirming the quality of a compressed transmission chain.
Strictly speaking, if anyone has reconstructed TCW in Flash it would be easy to up it to HD resolution simply by increasing the output size accordingly.
When TCW was designed the central image of Carole was rescanned from the original slide using the most powerful scientific scanning equipment available, so there shouldn't be a problem with HD compatibility.
I think the testcard generating algorithm was written in a high-level computer language - Richard Russell's site may have more details. Pretty certain it was more likely to be something like C rather than Flash - to generate a decent test card you can't just render a vector representation to a given raster resolution, you need to ensure things like the shape of the gratings are mathematically correct etc.
One thing many computer-centric folk forget is that TV is based around samples NOT pixels...
The current Testcard W is generated in software (i.e. the gratings are generated from mathematical formulae - not simply images). It it thus possible to create it at different resolutions - and modify the resolution of the gratings etc.
The HD testcard can thus be generated in a similar manner to the SD one. I believe the original still picture of the girl and clown has been scanned at high resolution.
Surely there's a need for any HD testcard to have some sort of moving element though? It couldn't be just a diffrent resolution version of TCW
It depends what you need the testcard to do - a static card still has uses for display line-up, but a moving element is useful for confirming the quality of a compressed transmission chain.
A bigger issue with lining up, is that a large amount of digital link equipment will freeze on the last valid frame when it looses it's signal. An animated portion of the image shows you are currently recieving an actual feed, rather than there was a valid signal recieved at some point.