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Author Topic: "High Definition"  (Read 7211 times)
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Posts: 157

« on: June 06, 2010, 04:13:56 PM »

What exactly does "High Definition" mean, and what kind of videos should be "allowed" to use this term?

I ask for two reasons.

1. Some people feel that only 1080p video is HD, or that 1080p is synonymous with HD. I have had some people insist that, say, a 720p video is not "really" HD. Others use the term HD to mean basically anything with more than the 480 scan lines of SDTV. And of course, that 480 comes from SDTV in HTSC format; is PAL it's a few more lines (can't recall exactly how many off the top of my head) and the frame rate is 50Hz with progressive scan, so that further muddies the waters.

Personally, I am happy applying HD to 720-line video or higher, but I am not sure if there's an official definition for this.

But the bigger problem is Item 2.

2. Some people also seem to feel that *anything* presented in 720 or 1080 resolution, or any HD format, is HD, regardless of the quality of the underlying video, and regardless of the encoding bit rate. For example, I've seen TV broadcasts at 720p (I don't have a 1080 TV yet) that clearly were encoded with an abysmally low bit rate. Is this HDTV? Maybe the FCC lets them call it that -- do they even regulate the use of the term "HD" for cable/satellite/airwave broadcast, or can any broadcaster stick HD onto any program content?

What does this have to do with fractals? Well, some animations are presented in 720 or 1080 or whatever format greater than 480 lines, and are labeled HD by their authors, but were most likely rendered at significantly less than that actual resolution at the time the actual fractal images were created.

There are many ways this can happen. It's easy to set a video compression program to output 1080 video from low-definition source files. Someone could calculate the fractal frames at, say, 960x540 and then set the encoding software to output 1080 video, a 2X step-up in resolution.

Another way this can happen is with the interpolation techniques that many of us use to make ultra-deep zooming possible. This is where a small number of pixels is used, with digital zooming and interpolation techniques, to generate video data for a large number of video frames. Since there's such a huge amount of redundant information from one frame to the next, only a small fraction of "new" data needs to be calculated to give a very good zooming effect. I have no problem with this, but it can be misused. If, say, a 1280x720 HD video is going to be made this way, it seems only fair to me to insist that every frame be interpolated from a master image with at least that many pixels -- there should be no "undersampling". It's not really HD to start with a 320x180 image and interpolate it up to 1280x720 video. Interpolating to HD resolution from a lower-resolution raw data set is no different than just setting the video encoder to output 1080 from standard-definition video.

I've elaborated on the topic of interpolation and undersampling on my web site at http://www.hpdz.net/TechInfo/Animation.htm#Frame_Interpolation.

Another trick to reduce computing time, file size, and bit rate is lowering the frame rate. Seems to me that 10 fps isn't HD no matter what the format or bit rate is. Movies, I believe, are usually 24 fps, but I think some might be faster, like the IMAX format.

Finally, there is the question of encoding bitrate. This is a hard problem, because there's so much detail in most fractal animations that anything less than an enormous bit rate tends to look blurry and blocky. But I think most would agree that encoding to at least DVD quality (4Mbps or so) should be part of presenting a final product designated as High-Definition, and in fact, 8-12 Mbps might be an even more satisfactory minimum. I know that YouTube etc probably don't deliver sustained bit rates that high, and not everyone has an internet connection that can sustain that speed. But the loss of detail resulting from the lower bit rates seem to me to cancel out the benefits of presentation in a 720 or 1080 format.

So I just wanted to open up this topic for discussion and see what people think.

I would suggest that those of us who create animations think carefully about the bit rate and resolution issue, as well as the use of undersampling when interpolating. To my eye, I would rather have a smooth, crisp 30 fps video at 320x240 than a blurry, blocky, jittery one at 15 fps 1920x1080.

Zoom deeply.
Posts: 135

« Reply #1 on: June 07, 2010, 04:29:48 AM »

I think it's best to think of HD as a set of video transmission and display standards for television (broadcast) and video playback on TVs & dedicated playback devices (like Blue-Ray).   (here is some info. for example http://www.cnet.com/hdtv-resolution/)

Computers aren't restricted as much as TVs and dedicated video devices are and have for a while been able to exceed the quality of the HD video standard.  "High definition" as an adjective, and the "high definition" video standards are kind of separate things in my mind.  I don't see any need to dispute what is HD and what isn't.  Something follows the HD standard if it matches one of the pre-defined resolution & frame rates.  Of course that naturally says nothing about it's clarity (which is getting into the adjective use of the phrase "HD" which uses the same words in a different context and meaning.

So I consider high-definition (video standard) and high-definition (clarity description) to be homophones - different words that sound the same (but have different meanings in this case.)  Because of the ease in confusing them, I think it's best to describe the clarity of videos with other adjectives like "I rendered this with high quality" or "high clarity" leaving "HD" only to refer to the resolution and frame rate of the video file.

Random side-note:  I live in Japan and they call it ハイビション which is literally the English phrase "high vision" spelled out in Japanese and pronounced with a Japanese accent.
« Last Edit: June 07, 2010, 04:37:45 AM by aluminumstudios » Logged
Fractal Fertilizer
Posts: 355

« Reply #2 on: June 07, 2010, 01:08:18 PM »

Hi, personally I could not upload a 320x240 video on youtube; the encoder finished the job but there was no video at the end and no explanation..upscaling was necessary to upload that video.
Regarding PAL signal: it's 768x576 interlaced lines and 25 images in one second, so would be called 576i25 (similar to dv codecs and SD DVD: 720x576 lines).
1080p50 would be 1920x1080, 1080 progressive lines and 50 frames in a second.
It's confusing on wikipedia, sometimes 50 is related to frames, sometimes not...while the editing would be made using 25 fps (?)..in USA would be 1080p60.
So 1080i would be effectively 1080/2 lines or pixels if not de-interlaced!
If we want to deinterlace 1080i we can choose to remove the blank lines or to create new ones artificially.
There's no problem of interlaced material (as far I know) talking about fractal-animations.
Personally I choose 'animation' as codec for the rendering and 'H.264' after the editing (quicktime files)..the real problem is to output HD files from GPU programs made for rendering fractals; it's still a problem..I hope it will change soon.
Ps:  720p is for sure HD, just consider video cameras as an example: panasonic HDVCPRO is much better than 1080i used on HDV codec; HDV has the same data rate (or less) than miniDV, around 11-12 giga x hour.
« Last Edit: June 07, 2010, 01:41:31 PM by visual » Logged
« Reply #3 on: March 05, 2011, 07:55:20 PM »

1080p plays fine on my pc, i prefer 1080p videos because youtube has the option to see them in 320 anyway
« Reply #4 on: July 14, 2011, 04:38:34 AM »

Becuase most of us will see these HD through the internet, what file size would a 10minute 1080p range around?  And if it wasnt to large, what video host (youtube) would display the best.?
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