Youtube HD doesn't make sense.

[Rye]

How can one watch hd vidoes in youtube for example without hd monitor - hows that possible?

I'm still able to see youtube videos in 'HD' quality however I'm a mac user.

[deathshadow]

HD in the simplest terms is anything higher than DVD resolution - which frankly is only 720x480 for us in the states or 720x576 for you pal folks...

720p is technically HD content - 1280x720. Your display shows more than 1280x720, right? Hell, it's why the majority of laptops right now are coming out at 1366x768 - just a hair more than 720p. The handful of pixel doubling is barely noticeable fullscreen, especially if pixel summing is used.

It also hinges on the encoder. H.264 has a very robust rescaling as part of it's spec - and resampling is common regardless of image size. Interscening for example averages the pixels not just resizing frames, but across multiple frames to smooth out movement and increase the apparent resolution using the same types of trickery as anti-aliasing - Tricking the eye into thinking it's seeing higher resolution than it actually is. 3d acceleration hardware can also be leveraged since they specialize in resizing texture images while minimizing appearance degradation. Mip-mapping, FSAA - all can be applied to a video frame so that while you might not be getting the quality stored in the data stream, you are at least getting the best quality your device can handle.

That's the key to 'reformatting' information. In the audio world there's a saying - garbage in, garbage out. Even if you are remixing down to a crappy little cassette tape release, you want to start with the highest quality studio masters.

Think of it this way, a 320x200 image resized to fit a 1920x1200 display is gonna look like ass - while a 1280x720 image scaled to 1920x1080 (1080p) will be entirely acceptable quality and scaled down to 320x200 will look great.

[Cohen]

i see the "HD" quality on the videos - i think it is very good. It is good especially when you want to show something on a projector - which often happens at school events.

[cbuckley]

To be honest HD could be anything because it just means it's higher than another definition. I see where you are going with HD but seriously what else would you have called it if you were youtube. If it said the exact resolutions then people would just end uip calling it HD anyway.

Also google has changed their "HD" mode now to say it like 720p.