DVCPro and DVCPro 50
Posted 11 April 2007 - 10:15 PM
Posted 11 April 2007 - 10:20 PM
DVCPro 50: 4:2:2, 50 Mbps, 3.3:1 compression ratio (double the coded video bitrate to DVCPro 25.)
Edited by Chayse Irvin, 11 April 2007 - 10:21 PM.
Posted 11 April 2007 - 10:50 PM
When you say 50Mbps, that means the rate at which the information is been received in to camera or recorded?
Whats the compression ratio.
Sorry if I seem amature but i want to learn and understand this once and for all.
Posted 12 April 2007 - 07:31 AM
What is the difference between the DVCPro and DVCPro 50 setting.
Ken, I'd like to propose a different type of answer.
All the technical numbers are great and can tell you things about the two, but the way television is made, they can be misleading.
Film and television acquisition is designed after how the eye sees. Our eyes see mostly through contrast with a small portion of our eye seeing in color. And with that color portion we don't see all colors equally well but we don't have to. Evolution developed an eye that saw what it needed to see. Most food was in shades of color from green to red so they were important. Green also meant safety as it represented places to hide such as the canopies of trees so in evolutionary terms may have had the most significance and perhaps why our eyes sees a large range of green well. Blue didn't represent much in terms of food, or safety so we don't have as many receptors in our eyes for blue.
And since video is like our eye/brain in how it sees it means we can afford to give away information and/or combine it. Look at formats as a box and information as blocks of wood that go in that box. First off, a box does not have to be filled completely to be properly packed. In fact in terms of how a TV picture is made, it often isn't filled up completely and doesn't have to be . Television was originally black and white. When the powers in charge added color, they could not throw away the old color system in favor of something completely new as it would cost too much to do, so they worked with what they had and figured out the best and most efficient way of adding color. Sort of like saying you try to find the straightest point between two lines. In the end they realized that the human eye did not need much color information based on how our eye sees. The color information they had to add to the black and white picture had to fix inside the same picture as what was black and white. Sort of like saying for years you had a box perfectly filled with blocks, and now how do we add a few more blocks. So compromises were made to allow color to be entered in the picture. In the box euphemism it meant cutting some of the cubes in halve so we could add the additional color information.
In television terms it meant cutting the amount of color information presented but remember our eye didn't really need it all to see well so we could. As I said, the eye doesn't need much color to be seen as color. And like the eye some colors are not represented as much as others so in the process of seeing color we didn't have to have a full box of color to appreciate it. And in simple terms from the get-go television was always a compromise of efficiency with information based on mimicking the eye and producing equipment that was within price ranges. It has not changed.
High definition is very much a compromise of adding more information to what already existed. Old fashion television used to use half of a screens efficiency having 525 lines of picture and 525 lines of blank picture (retrace). High definition utilized those 'dark' areas giving you twice the picture so once again it was working with what we had but making it more efficient (changing the way we put blocks in the same box.
In analog days it was easy to cut the cubes in the box into smaller pieces to get more types of information in the box. In the digital world, it's easier to compress the information to fit in the same place. Some might say compression is like squishing the imaginary cubes down so you can fit more into the box. Actually it's not. Compression is giving up parts of information that you again can loose without missing.
In terms of color numbers like 4:2:2, you have nothing more than a digital method of giving up information you don't need. You will hear numbers like 4:1:1, 4:2:2 mentioned. One sounds better than the other. But it's not simply about better but how can you present information efficiently without anyone noticing. Show anyone two sources of video tape codecs on a TV set, one having 4:1:1 color sampling space and the other having what sounds like twice as much as in 4:2:2 and no one will be able to tell you the difference by itself. Rather remember what I said in the beginning about how we see, contrast is more import to our eyes than color. So if you want to be able 'better' pictures, you sample more information and then add the appropriate amount of color information. Basically, if you start with a bigger sample you can usually add more more color information and you get more robust picture. And a more robust picture means you can manipulate it more easily.
And that is why we have differences in formats. For you at home, simply replaying formats on a TV without having to process the information in editing, you don't need much to start with. Rather you can compress the information in away that is efficient and appropriate. But if you plan on doing manipulation, then a more robust format helps you do that better. Also viewing that information as in a where you see it determines what you need to start out with. If I had five pieces of candy for five people everyone would be happy. But if you had twenty people, you'd have to start out with more. You could split up the candy so everyone gets a taste, but to satisfy everyone you want to start out with more.
The bigger a screen you have to view on (the difference between a TV set and a theater screen not a 27 inch set and a 40 inch set) the more information you need to cover that screen properly so you dont notice the efficiency process of throwing away what you don't need in the first place. A format like DVCpro would offer less information than would DVCpro 50 on a big screen. And DVCpro 50 would offer less information than a more robust format like DVC pro HD. So, we have many formats each designed for different applications. Dvcpro also called Dvcpro 25 was originally used for the application of new gathering. It offered enough reproduction to work well enough for watching news. DVC pro 50 offered 'double' the amount of information and was designed for more robust needs where more editing and manipulation of the picture was necessary.
With more sampling, you had more information to work with sort of like two cars, one with a small engine and one with a large engine. For going to work the four cylinder engine will get you there but the car with the more robust engine can offer you more performance for when you need to do more than simply get to work. And in some cases you can push the limits of a format to do more than you might on an ordinary day. For instance a movie such as "28 days later" was shown in theaters. It was shot on a consumer format (DV) but was able to play well enough to see on a big screen. By a consumer format, I mean a format designed for folks at home to make home videos. While the filmmakers would have had a more visually appealing film if they had used a more robust format, their budget didn't allow it. When you can afford it, you pick a more robust format.
So it goes both ways but with two distinctions. As professionals we try to use the most robust format we can because after all the editing, dubbing and processing what we start with gets lost somewhat along the way. Sometimes budget does not allow what we want so we make compromises. If you had a video camera that you needed for making home movies, you would not need such a robust format. It's just like Dvcpro which was invented and utilized for the most part for news which didn?t need much to work well. It can be used for more robust work, but suffers in image quality when you push its limits. Sort of like stretching 4 inches of Saran wrap over a 6 inch bowl. But start out with 8 inch of wrap and you don't have to stretch it as much to make it work well.
Along with the introduction of digital formats came less expensive ways of producing better quality for the masses. And as added value many of the cameras today offer a few ways of recoding as long as they are all based on the same methods. Since DV is the same way of recording at DVCpro 50, just not as robust, it's easier to flip a switch and offer both. In some cases you might need the four cylinder car, and in others you might need the performance. And from a marketing perspective (how they sell a camera) offering more for the buck seems like value. It's sort of like how they used to sell VHS machines. You could buy a simple VHS machine. Or one what offered quality slo motion, and others that offered super VHS ways of recording. And some models had more bells and whistles. Often you never needed the bells and whistles but it sold more units.
But like your eyes its all about offering quality while finding the most efficient ways of presenting the information, while offering different levels of robustness for different applications.
A few years ago we called DV cameras like the DVX100 prosumer meaning they fit the bill between what folks used as home cameras and professional cameras, sort of a semi professional camera. It did what it had to do, did it well, and was designed so it was affordable. The HVX200 is the HD version of that camera. Some folks buy it to record pictures of their family, others buy it because they are professional wedding videographers, and others to do corporate work. Some use it a supplemental cameras for television work, and others have even used it to make low budget movies to show on a big screen. There are more robust cameras and formats but often price dictates what people can afford to use, so manufactures offer various settings for various applications.
So to answer the question you ask, the difference between to two formats is robustness. Both will work well, but one offers a bit more quality for times when you need to process the information more as in editing, color correction, etc. Imagine trying to get water from the reservoir to the city. With one pipe you can do it. But one pipe means everything has to travel down that one pipe. And that might mean more pressure as demand increases sometimes pushing the limits of the pipe. But if you had two pipes, you could spread the water out and both pipes would not have to work as hard. DVC pro is like two pipes, taking the same information and sending it down the pipe more easily and hence being able to deal more with fluctuations in colors and other values when you manipulate it later for viewing.
I hope this rambling analogous post helps.
Posted 13 April 2007 - 03:49 AM
Once again thank you.
Posted 29 April 2007 - 04:54 PM
At first I thought it would have been amazing if this information could have been stored onto a DV tape.
But I soon found out only DV to the tape. DVCPRO, DVCPRO50, and DVCPRO HD to P2 cards.
One of the reasons one would then use any setting other than DVCPRO HD would be to conserve space on the cards.