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Don't get me wrong 10 years ago I had no idea about how video capturing work besides what the average joe knows and the only reason I had to learn it is not because I want a business, but because the so called "professionals" who use $69 VHS/DVD combo from Walmart in their basement and call it a business screwed up our family tapes that I had to do all over again which one of them was chewed up by his cheap VCR, You probably know by now why I'm pissed. |
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The answer I got from you was kind of like "are you dumb??? its not possible, where have you been living these 2 decades??" All I did was simply ask if kind of machine exist, because as an engineer I cant find a *physical* reason that this kind of machine can not be possible. luckly dpalomaki answer that question that it is possible but from economic reason this machine does not exist. You didn't tell me that, you just tried to whack like i am saying some sick impossible physical thing. next time have some faith |
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and i did got the answer. so I understand :) I just simply ask what is the difference, I wanted to know exactly instead of just saying this youtube is a shit talker, and this elgato device is shit. |
A simple look at what make the 2x speed copying of analog video tape like VHS difficult is the mechanics and electro-magnetics of the information recorded on the tape.
While mechanically moving the tape faster is not difficult, we have SP, LP and EP tape speeds already, and getting the linear track (analog) audio would not be difficult, we would just have to digitally frequency shift it down to the normal range from the "chipmunk" sound range. To preserve its nominal 10 kHz frequency response would mean sampling at 48 kHz, no big deal, and playback as if sampled at 24 kHz. The more difficult item is the video and HiFi audio recorded on the tape. It is read by a spinning head in a helical scan, one frame (two fields) per rotation of the head along a track rotated diagonally across the tape. The physical tape speed sets the track pitch, the RPM of the spinning drum sets the speed of the head over the tape (corresponds to the ips of analog audio tape). At SP the tape speed is about 1.3 ips, the head speed over the tape is more like 222 ips. (Thus the primary driver between SP, LP, and EP recording quality is track width/pitch.) The video and HiFi sound information on the tape is recorded on tape as modulated RF signals. HiFi sound is FM modulated at 1.3 and 1.7 mHz center frequencies, color difference is AM modulated with a center frequency around 629 kHz, and luma is FM modulated in the range of 5.4 to 7 mHz (for S-VHS, and not counting sidebands). If you move the tape 2x speed, you need to spin the head 2x faster to capture the frame. Otherwise the head will be reading half of two adjacent tracks. (You can get an idea of this when you do a FFD/REW scan of a tape with a normal VCR.) Of course then you need to double the bandwidth and center frequencies of everything involved with decoding the stream read off the tape. You would have to digitize your output chroma and luma streams each to a pair of 8-bit 29 mHz sample rate streams (to preserve 4:2:2 color and resolution) and then decode as if 14.5 mHz sample rate to recover the signals. That translates to 464 mbps data stream. Alternatively you could build a special dual path VCR with a head mechanism that has double the heads, spin it at the normal speed, and have dual processing path electronics read two fields per revolution (ont one) and trust to digitizing electronics to combine the signals and get the frame and field order right. There is probably a design and patent for such a box already out there - just no viable market. The notes that "Elgato is crap " and similar statements made about other gear means that it does not meet the high standards of most of the participants of this board. Reasons vary and may include reliability, ability to deal with poor signal streams (e.g., weak sync and/or drop outs), ability to accurately digitize a signal, introduction of artifacts, and so on. That the gear survives on the market means that it meets the requirements of some buyers. One pays one's money and takes one's chances. |
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Old/used gear is an unknown - it might work or it might need overhaul/repair. Plastic parts age and get brittle, rubber parts deteriorate, stretch, etc., lub dries out, and so on. Without testing there is no way to be sure of what you might be buying. Maintenance/repair/parts support for anything more than ~7 or so years old is problematic. Bottom line is buy from trusted sources or be prepared for disappointment.
It may work OK for some tapes. It may struggle with some tapes. A good, clean tape with low noise video on it may copy nicely to the DVD. The result will not be suitable for video restoration/clean-up work. However, it might meet your quality expectations. No one else here can make that decision for you. Only you know how good is "good enough" for you. It will be a quick and dirty copy to DVD. And it copies in real time - a two hour tape takes 2 hours plus setup time. If you post the make/model someone here may have information on its quality potential. (Or search the site for posts about it.) |
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