Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site nicmad.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!think!harvard!uwvax!astroatc!nicmad!brown From: brown@nicmad.UUCP Newsgroups: net.analog,net.misc,net.tv Subject: Re: TV & VCR standards Message-ID: <522@nicmad.UUCP> Date: Sun, 19-Jan-86 23:36:38 EST Article-I.D.: nicmad.522 Posted: Sun Jan 19 23:36:38 1986 Date-Received: Tue, 21-Jan-86 07:38:52 EST References: <137@daisy.UUCP> <512@nicmad.UUCP> <395@packard.UUCP> <515@nicmad.UUCP> <423@unccvax.unccvax.UUCP> Reply-To: brown@nicmad.UUCP (Mr. Video) Organization: Nicolet Instrument Corp. Madison WI Lines: 132 Xref: watmath net.analog:636 net.misc:9164 net.tv:3894 In article <423@unccvax.unccvax.UUCP> dsi@unccvax.UUCP writes: >> In article <395@packard.UUCP> aat@packard.UUCP (AA Triolo) writes: >> > He told me it could be copied digitally for about >> >$175 for a two hour tape. He said the quality of the tape >> >would suffer however. I should expect colors to wash-out >> >and at times could lose verticle hold. >> >> Boy, is that guy full of shit. A digitally converted copy will actually >> >> Mr. Video >> >> > Whoooooooaaaaaa, there, Mr. Consumer Video... You just >might recall that the EBU broadcast primaries are different from the NTSC >broadcast primaries. The two colour gamuts (particularly with respect to >gamma precompensation) are not directly compatible, although it is possible >to get a pleasing aesthetic result. Colour correction is an extremely >expensive proposition which * no one * does for $175/2hr tape. Yes, the two color schemes are different. The results that I have gotton from the tapes I had converted are indeed just fine. If I had my druthers, I would rather watch PAL stuff on PAL equipment. But, that makes it hard to make copies. I have had VHS PAL converted to 3/4" Umatic NTSC for less than $175/2hr. It was also done on a Digital frame-store converter. The price: $80/hr. This was a little private operation that was not big company run and he is not out to make millions. > As for "jitters", there are good and bad line + frame interpolation schemes. >The first frame store PAL-B to NTSC-M converters suffer from severe motion >artifacts, such as the "jerky" tennis ball we've all seen during Wimbledon >matches of days gone by. Early "Muppet Show" tapes are also subject to >severe temporal jitter. The converter at my spouse's former employer was >horrendous in this respect. > > Yes, I agree that any digital frame store converter (which is not even >slightly the same thing as a TBC) should reinsert the sync and burst in >precise SC-H relationship for NTSC. However, the ability of the digital >frame store converter to follow the original input signal is compromised >by a consumer VTR recording. These are typically subject to gyroscopic >errors, long time constants in the servo loop controlling headwheel speed >and phase (done presumably to minimise "breakup" on cheap TV sets) and >very high amounts of subcarrier frequency modulation from line to line >due to stiction around the headwheel, etc....The input frame store has >to recover a sampling clock from all this crud, and it also has to determine >* which field is which * from trashy input synchronising information. >Thus, a marginal PAL-B home videotape may actually *appear to roll* >because the input converter has lost genlock. The image would still >* be fully framed * at the output. > > I don't think the guy was full of BS at all. When you start with a >trashy, timebase/frequency modulated signal that comes from consumer junk, >the possibility of successful conversions are fairly low. I might add >that professional equipment assumes (in many cases) a priori that there >isn't a lot of IFPM on the timebase or colour subcarrier signals, so that >the correction loop bandwidth is small where the write clock and timing are >recovered. Thus, most professional video equipment has a very hard time >genlocking to trash like VHS and Beta. The Sony 3/4" decks that I have at home don't have any trouble locking onto the output of any of the VHS tapes I have recorded. I prefer to record them on 3/4" first. But sometimes something goes wrong (me) and I have to use the VHS backup tape. > One can only hope that a uniform digital videotape standard will finally >filter down to consumers so that they can see what they've been missing. >I've given up on the public demanding 4.2 mHz luminance bandwidth for >now (but, yessirreee, they'll buy HDTV.) Sure, I'll buy HDTV. It is the only standard (or hope to be standard) that is wide screen and looks like it will have digital recorders from the beginning. >Mr. (Professional) Video >David Anthony >Director of Engineering >DataSpan, Inc. If you would like I could find out the exact model number of the converter that he is using. But, the proof is on the pudding. I have 13 45 minute tapes that were converted from VHS PAL to 3/4", like I said, that are some of the best copies that I have seen, from VHS PAL. There aren't any vertical problems. I guess I shouldn't say that. A couple of times the picture would jerk. Why, cause I saw that the original master tape had a problem in it. The digital converter just gave a minor hick-up and went on converting. No sync loss, etc. But, a couple of times out of 13 45 minute tapes is excellent. None of this vertical roll that the other person said would happen. The only problems that I had with the tapes was with the 3/4" tape. It tended to lose tracking around the vertical sync, causing the recorder, when editing, to lose sync on the copy. I have a NTSC sync generator chip that I put together years ago, but when connected to the Sony recorder, wouldn't work. Well, after enough of this problem (after all of the editing was finished) I decided to open the Sony deck and find out why the chip wouldn't work. As it turned out, the input circuit loaded down the TTL signal that I was supplying it, so that it couldn't trip the internal circuitry. With that fixed, I don't have to worry about bad tape messing up the recorder. I digress, but the main point is that you shouldn't put down digital converters until you have seen them all. In your job, you probably have seen most of them. Also, if you were to see these tapes, you would probably find something wrong with them. But, for the original poster, a tape converted by my source would probably work out just fine, which was what he was after. I think that the person who told the poster that he would have lots of problems was indeed full of BS. In your job, you are looking for perfection. I too would love perfect copies. I would love to spend $250,000 for a full 1"C editing suite, but don't have the money, so I stick with 3/4" for editing. I would love to have my mother-in-law have 3/4" equipment to record stuff for me (in England), but that is out the question too. I work with what I have and that is all the original poster wanted to do. I feel that he was scared off for no real reason. True, the results will not look as good as if it was recorded on VHS PAL, but it won't be as bad as the guy told the poster. I think that I have said enough. Mike Brown Consumer Video User that would love industrial video PS: I belive that discussions like this, will in the long run, help out other users on the net. I hope that you think so too. -- ihnp4------\ harvard-\ \ Mr. Video seismo!uwvax!nicmad!brown topaz-/ / decvax------/