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WHY SD HDV? WAT IS THE DIFFERENCE IF IT IS STILL SD?


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#1 john Spear

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Posted 18 September 2009 - 10:49 AM

What good is shooting SD HDV on the JVC GY110U if you can shoot HD or shoot SD? Why woul you want to shoot SD HDV and why does it hold the name HDV if it is still SD? I have never used it yet, altough I've used 60I and HD. What is the best scenario for SD HDV?


Anyone?
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#2 Thomas James

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Posted 19 September 2009 - 12:13 PM

Progressive scan 480p60 has twice the resolution of 480i which is interlaced. Also 480p60 has twice the temporal resolution of 720p30 so 480p60 will produce a sharper image than 720p30 if fast action sports are shot. Technically 480p60 is not a high definition format however the quality is good and it will be simular to high definition. Also since 480p60 uses a short gop compression it is easier to convert to full high definition 480p120 when viewed on a 120 hertz monitor.
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#3 john Spear

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Posted 07 December 2009 - 04:36 AM

Very Kool... Thanx...
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#4 Brian Drysdale

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Posted 07 December 2009 - 05:07 AM

I should point out that Thomas James has an obsession about temporal resolution and I suspect he didn't answer your question.

The argument tends to go that shooting HDV for SD delivery means that you're carrying more visual information into your workflow. That allows the much cheaper HDV cameras to produce images that compare better with the higher end 2/3" SD cameras (which often have the same number of sensor pixels as the HDV cameras). This does work to some extent, although the better glass on the high end cameras. plus their often used low compression 10bit 4:2:2 does tend to make a difference.

Likewise, 2/3" HDCAM does usually look better than something shot on a 2/3" SD camera for standard definition transmission, but that's not always the case, the PAL progressive frame digibeta can look better on SD.
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#5 john Spear

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Posted 08 December 2009 - 08:46 PM

Huhumm, I see... Now the difference is coming into focus...

Thanx for that...
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#6 Thomas James

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Posted 14 December 2009 - 06:24 PM

480p60 is not a supported format for either DVD or Blu-Ray delivery however it can be upconverted to 720p60. The Playstation 3 is the only player that will support 480p60 if a DATA DVD is burned. 480p60 is a broadcasting format that is fully supported and has advantages over 1080i because it is less compressed so the picture quality may be better than 1080i because it won't break up under fast motion. The vertical resolution of 480p60 is almost the same as 1080i which in reality is only 540 lines for each field. However 480p60 which is a picture quality success that rivals 1080i can only be a marketing failure because people assume that 480p60 is merely standard definition even though it is very difficult to distinguish from high definition.
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#7 Brian Drysdale

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Posted 15 December 2009 - 04:26 AM

I believe approx 700 lines vertical resolution is the accepted figure for 1080i.

http://en.wikipedia....iki/Kell_factor
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#8 Thomas James

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Posted 15 December 2009 - 04:11 PM

That is not entirely correct. HDV 1080i may resolve 700 or even 800 lines of resolution when the motion is relatively still however this resolution is cut in half to a low definition 350 to 400 lines during sequences of fast action. So the average resolution performance of the HDV 1080i format is closer to 540 lines than it is to 1080 which is very close to HDV standard definition. The horizontal resolution of HDV 1080i goes up to 1440 lines however the ratio of horizontal to vertical resolving power is so lopsided that this confuses the human psycho visual perception system causing this extra resolution to be thrown out. Therefore the actual resolving power of the HDV 1080i format is only 960x540 which is only 50 percent more resolution than HDV standard definition 480p60. Although not much better than HDV progressive scan standard definition, HDV 1080i requires 4 times the amount of information that needs to be digitally compressed resulting in horrible artifacting when the codec is overloaded. On the other hand HDV 480p60 does not break down during fast action and has a much superior 6 frame short group of picture mpeg-2 compression which means a total of 10 discrete I frames produced each second versus long GOP HDV 1080i which only has 2 discrete I frames created each second.
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#9 Brian Drysdale

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Posted 15 December 2009 - 05:14 PM

Most television or even in the movies isn't fast action, mostly it's just people walking and talking and many scenes are actually pretty static. It's the resolution of the wide shot that makes the difference in the storytelling, not the fidelity of the high speed action (which is commonly shot at 24fps anyway).

The figure you are referring to is the vertical resolution, the horizontal resolution is higher on 1080i. I must admit this is the first time I've heard NTSC figures being compared to HD, I suspect 1080i found favour with the BBC because, 720p isn't a stunning improvement over PAL.

Much of the problem lies with the distribution chain, which tries to squeeze too many channels into the available bandwidth.
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#10 Thomas James

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Posted 15 December 2009 - 05:47 PM

The only reason why the BBC finds favor with 1080i over 720p is purely marketing. 720p doesn't sound like a big improvement over PAL 625, So the BBC chose 1080i because 1080i has better sounding quality. So while so called full high definition 1080i has the best sounding quality of any high definition format it is in fact a picture quality failure. Can you imagine any video engineer in today's world that would still advocate a scrambled picture such as interlace scanning ? That would be insane to say that interlace is better than progressive scanning. But it is not the video engineers that have the final say but rather the marketing department. Big resolution numbers sell televisions and big resolution numbers make people buy into full high definition 1080i broadcasting even though interlace scanning is totally incompatible with the newest generation of natively progressive flat panel displays.

And while interlace scanning is a very crude form of video compression it is also the least intelligent. Interlace scanning wipes out and throws away entire rows of video information making it very hard for a televisions interpolation software. If they were going to throw out these massive amounts of information the least they could is to leave a checkerboard pattern so that there would be 4 surrounding pixels in order to make an accurate guess of each pixel in the center.
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#11 Brian Drysdale

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Posted 15 December 2009 - 06:24 PM

The horizontal resolution of 1080i is higher than 720p and I understand the alternative was the EBU favourite 1080p25, which wouldn't have been so good for sport.

Engineers tend to be practical people, they use what works and often go for the best compromise solution. 1080i reduces the bandwidth requirements compared to 1080p50. These decisions were probably taken 10 years ago, so any limitations were those that had to be taken into consideration during that decision period. I suspect 1080p50 would still cause problems for a mainstream TV system.
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#12 Thomas James

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Posted 15 December 2009 - 06:49 PM

Again the BBC engineers are wrong. It is dubious to say that 1080i can reduce any bandwidth requirements compared to 1080p50. All of this is a result of analog thinking where using analog technology it is reasonable to believe that interlacing can save bandwidth. However analog engineers assume that their crude compression strategies which barely work for analog will also work for digital and this is not true because when using digital, interlace compression is very inefficient. Unfortunately there is a lack of 1080p50 cameras on the market unless you want to include the Red which is more optimized for cinema rather than broadcasting. I think part of the problem is that there is a legacy of interlace broadcasting and television engineers refuse to admit that they were wrong all of these years.

However the computer industry dumped interlace scanning years ago because they did not want to risk paying out workman's compensation claims to workers suffering eyestrain trying to read and write text using those miserable interlace flickering monitors always known to chop off the tops of all the letters. It may seem like a joke but many industries have in place tough ergonomic standards that must be complied with.
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#13 Brian Drysdale

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Posted 16 December 2009 - 04:23 AM

These decisions were made on during the days of Windows 95 & 98, so modern IT technology wouldn't have entered into the equation, only what was possible when the decision were being made.

Interlace may or may not be a crude method, personally I see crude compression all the time in the digital transmission chains.
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#14 Thomas James

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Posted 16 December 2009 - 05:30 PM

Certainly the concept of interlacing cannot be entirely dismissed. Texas Instruments has used a type of interlacing called wobulation technology that gives the illusion of doubling or even quadrupling the native resolution of the display device. And of course pixel shifting is also a technique similar to interlacing which can at least theoretically infinitely increase the resolution of a camera. So indeed it is possible to build up a high quality complete frame using interlace fields. However one must remember that advanced interlacing runs at much higher speeds such as 600 hertz than traditional interlacing which is only 60 hertz, uses overlapping technology so that the picture is seamlessly blended rather than creating a screen door effect and the goal of advanced interlacing is to create a picture that is indistiguishable from a progressively scanned picture yet at a much lower cost.
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