Tech Tips:
Understanding DVCPro
By Andy DunnDVCPro, by any name, will still be confusing. It doesn’t seem like this should be difficult to understand, right? I mean you use BetaSP tape in a BetaSP camera or deck and DigiBeta Tape in a DigiBeta camera or deck. Then what makes this format so confusing to so many of us?
Although it may seem right to assign the format to a particular camera or recorder, these days, you can’t do that, especially with this format. There are 3 DVCPro formats distinguished by the amount of information they work with (capture, record, or play) in a second. (Technically there are 4 but I will get back to that later. The DVCPro25 format handles 25 Megabits of information every second. The DVCPro50 formats can handle 50 Megabits per second of information while the DVCPro100 deals with 100 Megabits per second. The last is a great deal of information and is currently used for Panasonic’s high definition applications and is more often referred to as DVCProHD. The first is often referred to simply as DVCPro and there is where the confusion begins.
So let’s recap. Yes, I know we just began, but this is important. DVCPro refers to capturing, recording or playing footage at 25 Megabits per second and may be referred to as DVCPro25 or DVCPro. DVCPro50 refers to capturing, recording or playing back footage at 50 Megabits per second. DVCProHD refers to capturing, recording, or playing back footage at 100 Megabits per second and may be called DVCPro 100 or DVCProHD
Now I present you with the most important news of all, All Tape Is Created Equal. All DVCPro XX tapes are the same. The color of the cartridge lid may be different, the size of the cassette may be different and even the number on the front may be different but the tape inside is the same.
DVCPro tapes come in size M, L or XL (medium, large or extra large). If you were to put this tape in a camera or recorder that records 25 Megabits per second (assuming it fit), you can be confident that the tape will last as long as the number of minutes printed on the front of the cassette. For example, a DVCPro AJ-P66MP tape is a Medium Play cassette and, when recording at 25 Megabits per second, will last 66 minutes.
If I took that tape and, instead, placed it in a 50 Megabit per second recorder, the tape would last 1/2 the time or 33 minutes. A 50 Megabit per second recorder moves the tape across the heads twice as fast as a 25 Megabit per second recorder. This allows the heads to cover more tape in 1 second and therefore allows for more information to be recorded during that second. Since the tape is moving at twice the speed, it only makes sense that it will last half as long.
If I took that same tape and, instead, placed it in a 100 Megabit per second recorder such as a Varicam, it would last 1/4th the time displayed on the cassette or approximately 17 minutes. The 100 Megabit per second recorder moves the tape at 4 times the speed as a 25 megabit per second recorder. This makes it possible to record a much greater amount of information in 1 second.
Now that you understand that, the same is true for the other tapes. DVCPro50 tape is often used in the Varicam HD camera. The camera records at 100 Megabits per second, not 50 so the number of minutes listed on the tape cassette will be cut in half.
Now that some of the confusion has been lifted, let me add another complexity. The Panasonic SDX 900 camera can be set to record at 50 Megabits per second or at 25 Megabits per second. The cameras at Rule, by default, are set at 50 Megabits per second and I have never seen anyone request otherwise. However, the camera only takes the MP cassette sizes (smaller) and the DVCPro50 cassettes only come in the LP size (larger). This means that the tape stock marked DVCPro50 will not fit in the camera recording at 50 Megabits per second.
Also, most DVCPro decks will play back multiple formats but often not all of them. For example, the DSR 1800 DVCam deck will record and play back in the DVCam format but it will also play a DVCPro tape recorded at DVCPro25. It will not play back that DVCPro tape if it was recorded at a DVCPro50 format (for example recorded on the SDX900 camera set at 50MB/s). The Panasonic AJ-SD930 recorder can be set to record in either the DVCPro25 or the DVCpro50 format just like the SDX900 camera. It will play back DV and DVCam tapes as well, even though it will not record in those formats, however, it cannot play back either format if recorded on a MiniDV cassette without an adapter and, even then, recording and playback options are limited.
Very slowly, the confusion lifts and the final wrench gets thrown into the mix: the Panasonic AJ-HD1700EX. This records in the new fourth format I mentioned earlier, DVCProEX. This deck will record at 100 Megabits per second just like the HDC-130 video recorder however, it does it on half the tape. I didn’t want to get too technical but this is pretty important. The distance between two adjacent tracks, measured from centerline to centerline is called the Track Pitch. In all DVCPro recording devices, the track pitch measured 18 microns. This means that the width of 1 track of information is 18 microns wide. The engineers at Panasonic have been able to cut that in half with the AJ-HD1700EX so that 1 track of information can be recorded on a piece of the tape only 9 microns wide. The big benefit here is that in that original 18 micron width of tape, you have twice the amount of information. Essentially 1 second of footage can now hold twice as much information as before. If you look at the cassette for DVCProHD tapes, there are 2 numbers listed. The larger number of minutes will only occur when recording on this new EX format.
The AJ-HD1700EX is backward compatible for playback. This deck will play back anything recorded on DV, DVCam (except MiniDV casettes), DVCPro, DVCPro50, DVCProHD, and DVCProEX formats. However, since this is the latest technology, any tape recorded on this deck can only be played back on another AJ-HD1700EX VTR. This is worth repeating. Currently, any recordings made on an AJ-HD1700EX video recorder can ONLY be played back on an AJ-HD1700EX video recorder. Some time soon, a new, smaller deck will come out in the same DVCProEX format but until then, this is it.
Ok, the confusion is at an end. Just re-read this document three times and say, “There’s no place like home”.
