From: dannyb@panix.com (danny burstein) Newsgroups: alt.folklore.computers Subject: field/frame, was: Re: video tape backup systems Date: 9 Mar 2000 00:27:20 -0500 Organization: "mostly unorganized" Lines: 33 Message-ID: <8a7cno$fvr$1@panix6.panix.com> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> NNTP-Posting-Host: panix6.panix.com X-Trace: news.panix.com 952579641 7473 166.84.0.231 (9 Mar 2000 05:27:21 GMT) X-Complaints-To: abuse@panix.com NNTP-Posting-Date: 9 Mar 2000 05:27:21 GMT X-Newsreader: NN version 6.5.6 (NOV) Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!news.maxwell.syr.edu!howland.erols.net!panix!news.panix.com!panix6.panix.com!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:51466 In <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> Brian Inglis writes: >>So how does the data capacity of these same videotapes keep getting >>bigger? From 20 meg to 4 gig, man. VCRs have always had pretty crap >>resolution haven't they? >Assuming mono encoding: >512 dot/line x 256 line/frame x 60 frame/s = 7.5Mb/s not quite. You're off by a factor of four... see below >7.5Mb/s x 60s/m x 60m/h x 2h = 54kMb ~ 52Gb ~ 6.5GB hmm, maybe a factor of two since you're saying 256 lines/frame rather than 525.. .. anyway.. standard (vhs) vcrs only record _one_ of the two fields out of each frame, so you're only getting 262 lines (out of 525) of resolution. (usally actually a bit less since many don't even bother with the overscan) (the fields alternate between the odd and even lines of the frame every 1/60th of a second, meaning the complete frame is 1/30th of a second) which means, btw, that the regular vcr (pretty much by definiton) loses half of the original signal. (Actually, of course, it's worse than that) -- _____________________________________________________ Knowledge may be power, but communications is the key dannyb@panix.com [to foil spammers, my address has been double rot-13 encoded] ###### From: "Simo Tuominen" Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: Thu, 9 Mar 2000 20:55:58 +0200 Organization: Heinrich Heine Universitaet Duesseldorf Lines: 56 Message-ID: <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> NNTP-Posting-Host: lan1.miu.uni-duesseldorf.de X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.2919.6600 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6600 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!isdnet!newsfeed.tli.de!fu-berlin.de!RRZ.Uni-Koeln.DE!news.rz.uni-duesseldorf.de!usenet Xref: chonsp.franklin.ch alt.folklore.computers:51546 "danny burstein" wrote in message news:8a7cno$fvr$1@panix6.panix.com... > In <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> Brian Inglis writes: > >>So how does the data capacity of these same videotapes keep getting > >>bigger? From 20 meg to 4 gig, man. VCRs have always had pretty crap > >>resolution haven't they? > > >Assuming mono encoding: > > >512 dot/line x 256 line/frame x 60 frame/s = 7.5Mb/s > > not quite. You're off by a factor of four... see below How come? What you're saying doesn't refute what he says. This is theoretical. > >7.5Mb/s x 60s/m x 60m/h x 2h = 54kMb ~ 52Gb ~ 6.5GB Um, Brian, exactly *why* did you change from the incorrect "b" to the correct "B" in mid-conversion? > hmm, maybe a factor of two since you're saying 256 lines/frame > rather than 525.. > > .. anyway.. > > standard (vhs) vcrs only record _one_ of the two fields out of each > frame, so you're only getting 262 lines (out of 525) of > resolution. (usally actually a bit less since many don't even bother with > the overscan) Did you stop to consider that he might know this, and use 256 lines in his calculation because of that? > (the fields alternate between the odd and even lines of the frame every > 1/60th of a second, meaning the complete frame is 1/30th of a second) > > which means, btw, that the regular vcr (pretty much by definiton) loses > half of the original signal. (Actually, of course, it's worse than that) Yep. A typical VCR records maybe 240 lines per two fields, so you lose a lot. Of course, I only know about PAL VCRs, but the magnitude is right. 512 bits per line is definitely too much anyway. 400 I'd believe. Maybe. ###### From: wolfi@berlin.snafu.de (Wolfgang Schwanke) Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: 10 Mar 2000 09:25:45 GMT Organization: [Posted via] Interactive Networx Lines: 27 Message-ID: <8aaf2p$8hn$1@unlisys.unlisys.net> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> NNTP-Posting-Host: fubar.snafu.de x-no-archive: yes X-Newsreader: NN version 6.5.0 #3 (NOV) Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!isdnet!newscore.gigabell.net!unlisys!news.snafu.de!wolfi Xref: chonsp.franklin.ch alt.folklore.computers:51504 dannyb@panix.com (danny burstein) writes: >.. anyway.. > standard (vhs) vcrs only record _one_ of the two fields out of each >frame, so you're only getting 262 lines (out of 525) of >resolution. (usally actually a bit less since many don't even bother with >the overscan) Uh, compolete nonsense. They record all lines of both fields (525 NTSC, 625 PAL/SECAM). They have no means to drop part of if even if they wanted, it would imply asynchronous recording (record a bit, wait a while, continue recording ...), which of course they don't. They record all the signal all the time. The quality problems of VHS are due to _bandwidth_: A broadcast TV signal has 5 MHz bandwidth (PAL world, NTSC is about 4 MHz). The mid-70s formats (VHS, Betamax, V2000 etc) record only 2 .. 2.5 MHz. That means that the signal loses definition along each line (left to right). Regards -- wolfi@techno.de + wolfi@snafu.de + http://www.snafu.de/~wolfi/ + IRC:wolfi you're sweet like da dadada dadada ###### From: Simon Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: Fri, 10 Mar 2000 11:57:24 +0000 Organization: Imperial College Lines: 47 Message-ID: <38C8E324.99E24FE8@ic.ac.uk> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> Reply-To: s.j.harris@ic.ac.uk NNTP-Posting-Host: andromeda.me.ic.ac.uk Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.7 [en] (Win95; I) X-Accept-Language: en Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!news-fra1.dfn.de!news0.de.colt.net!colt.net!newsfeed.icl.net!news.vas-net.net!server2.netnews.ja.net!server6.netnews.ja.net!server4.netnews.ja.net!news.cc.ic.ac.uk!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:51543 Simo Tuominen wrote: > > "danny burstein" wrote in message > news:8a7cno$fvr$1@panix6.panix.com... > > > (the fields alternate between the odd and even lines of the frame > every > > 1/60th of a second, meaning the complete frame is 1/30th of a > second) > > > > which means, btw, that the regular vcr (pretty much by definiton) > loses > > half of the original signal. (Actually, of course, it's worse than > that) > > Yep. A typical VCR records maybe 240 lines per two fields, so you lose > a lot. Of course, I only know about PAL VCRs, but the magnitude is > right. 512 bits per line is definitely too much anyway. 400 I'd > believe. Maybe. VCRs record both fields of a video frame, so there is not a huge amount of data loss from line reduction. The only thing that is lost is the interlace signal, so whereas normal TV is 480/580* lines (approx) at 30/25 Hz frame rate, VHS pictures are approx. 240/290* lines at 60/50 Hz frame rate. If I understand correctly SVHS preserves the interlace pulses. As others have said, however, the bandwidth along each line is pretty poor on VHS. *I don't have the exact figures to hand for the number of picture lines in a frame - but it's something around this. Simon. -- -------------------------------------------------------------------------- Dr. Simon J. Harris email: s.j.harris@ic.ac.uk Mechatronics in Medicine Laboratory, tel: 0171 589-5111 x 57068 Department of Mechanical Engineering, http://www.me.ic.ac.uk/case/mim Imperial College of Science, Technology and Medicine, Exhibition Road, London SW7 2BX -------------------------------------------------------------------------- Carlton Dramatic Society web site: http://come.to/carltondrama -------------------------------------------------------------------------- ###### From: Jim Stewart Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: Fri, 10 Mar 2000 08:38:13 -0800 Organization: http://www.jkmicro.com Lines: 42 Message-ID: <96A6D088EF5292BB.F33A600BA31A8CE7.EBC6A26177D83CB0@lp.airnews.net> X-Orig-Message-ID: <38C924F5.B7D95CB4@jkmicro.com> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> Reply-To: jstewart@jkmicro.com Abuse-Reports-To: abuse at airmail.net to report improper postings NNTP-Proxy-Relay: 204.181.96.50 NNTP-Posting-Time: Fri Mar 10 10:36:04 2000 NNTP-Posting-Host: !Yg>61k-Va[Ao0CG]a[;EbB > Simo Tuominen wrote: > > > > "danny burstein" wrote in message > > news:8a7cno$fvr$1@panix6.panix.com... > > > > > (the fields alternate between the odd and even lines of the frame > > every > > > 1/60th of a second, meaning the complete frame is 1/30th of a > > second) > > > > > > which means, btw, that the regular vcr (pretty much by definiton) > > loses > > > half of the original signal. (Actually, of course, it's worse than > > that) > > > > Yep. A typical VCR records maybe 240 lines per two fields, so you lose > > a lot. Of course, I only know about PAL VCRs, but the magnitude is > > right. 512 bits per line is definitely too much anyway. 400 I'd > > believe. Maybe. > > VCRs record both fields of a video frame, so there is not a huge amount > of data loss from line reduction. The only thing that is lost is the > interlace signal, so whereas normal TV is 480/580* lines (approx) at > 30/25 Hz frame rate, VHS pictures are approx. 240/290* lines at > 60/50 Hz frame rate. If I understand correctly SVHS preserves the > interlace pulses. The VHS machines have what's called "random interlace". There's no guarantee that fields will interlace and there's no guarantee that they won't. The average vertical resolution will be considerably better than 240/290. Running the signal through a time base corrector will sort it all out. The infamous and thankfully dead Cartravison system recorded a single field and played it back twice to double the recording time. There was noticable flicker in the system. -Jim ###### From: "Mark P." Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: Fri, 10 Mar 2000 15:59:35 -0500 Organization: Posted via Supernews, http://www.supernews.com Lines: 23 Message-ID: <38C96236.ED74FA18@indyice.com> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> <96A6D088EF5292BB.F33A600BA31A8CE7.EBC6A26177D83CB0@lp.airnews.net> X-Complaints-To: newsabuse@supernews.com X-Mailer: Mozilla 4.7 [en]C-CCK-MCD NSCPCD47 (Win95; I) X-Accept-Language: en MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!newscore.univie.ac.at!194.25.134.126.MISMATCH!newsfeed01.sul.t-online.de!t-online.de!newsfeed.tli.de!newsfeed.icl.net!europa.netcrusader.net!209.150.97.11!feeder.qis.net!news.maxwell.syr.edu!newsfeed.stanford.edu!remarQ70!supernews.com!rQ66!corp.supernews.com!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:51597 Jim Stewart wrote: > The infamous and thankfully dead Cartravison system recorded a single > field and played it back twice to double the recording time. There was > noticable flicker in the system. > > -Jim Worse than that, it recorded and played back 1 to 3. OBcomputer-like folklore: some of the circuits used RTL logic gates. Still the proud(?){dubious} owner of a Cartrivision. Who says electronic antiques have to be computers. -- Note: I don't have "X" in my address. ###### Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: Fri, 10 Mar 2000 14:05:27 -0800 Organization: http://www.jkmicro.com Lines: 22 Message-ID: <026EBF9A7F0B8C0C.05D1851294A216B3.F52925059D11774A@lp.airnews.net> X-Orig-Message-ID: <38C971A7.17A9B55F@jkmicro.com> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> <96A6D088EF5292BB.F33A600BA31A8CE7.EBC6A26177D83CB0@lp.airnews.net> <38C96236.ED74FA18@indyice.com> Reply-To: jstewart@jkmicro.com Abuse-Reports-To: abuse at airmail.net to report improper postings NNTP-Proxy-Relay: 204.181.96.50 NNTP-Posting-Time: Fri Mar 10 16:03:21 2000 NNTP-Posting-Host: !Y=rL1k-W\Y1f4"G]a[;EbB<. (Encoded at Airnews!) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 4.61 [en] (Win98; I) X-Accept-Language: en X-Original-NNTP-Posting-Host: 209.233.102.221 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!isdnet!howland.erols.net!outgoing.news.rcn.net.MISMATCH!feed1.news.rcn.net!rcn!nntp.giganews.com!cabal14.airnews.net!news.airnews.net!cabal1.airnews.net!news-f.iadfw.net!jim.!209.233.102.221 Xref: chonsp.franklin.ch alt.folklore.computers:51599 "Mark P." wrote: > > Jim Stewart wrote: > > > The infamous and thankfully dead Cartravison system recorded a single > > field and played it back twice to double the recording time. There was > > noticable flicker in the system. > > > > -Jim > > Worse than that, it recorded and played back 1 to 3. > > OBcomputer-like folklore: some of the circuits used RTL logic gates. > > Still the proud(?){dubious} owner of a Cartrivision. Who says electronic > antiques have to be computers. As a matter of fact, I do remember 3 heads on the drum. And I also retyped the name 2 or 3 times trying to figure out whether it was spelled with an "a" or an "i". ###### From: greenaum@BOLLOCKSyahoo.co.uk Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Organization: Rossum's Universal Robots Reply-To: greenaum@BOLLOCKSyahoo.co.uk Message-ID: <38cd56f2.9397381@news.freeuk.net> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> <96A6D088EF5292BB.F33A600BA31A8CE7.EBC6A26177D83CB0@lp.airnews.net> X-Newsreader: Forte Agent 1.5/32.452 X-No-Archive: yes MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 10 Date: Sat, 11 Mar 2000 14:27:05 GMT NNTP-Posting-Host: 212.126.146.39 X-Complaints-To: abuse@freeuk.net X-Trace: nnrp4.clara.net 952784825 212.126.146.39 (Sat, 11 Mar 2000 14:27:05 GMT) NNTP-Posting-Date: Sat, 11 Mar 2000 14:27:05 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!newscore.univie.ac.at!194.25.134.126.MISMATCH!newsfeed01.sul.t-online.de!t-online.de!newsfeed.tli.de!newsfeed.icl.net!newspeer.clara.net!news.clara.net!nnrp4.clara.net.POSTED!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:51626 What, so you could double the quality of any VHS picture by running it through a time-base corrector? By tarting up the sync pulses a bit? Why don't they? ------------------------------------------------------------------------ Why pamper life's complexity, when the leather runs smooth on the passenger seee-eee-aaat? - - - - - - - - greenaum@yahoo.co.uk ###### From: wolfi@berlin.snafu.de (Wolfgang Schwanke) Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: 11 Mar 2000 15:38:35 GMT Organization: [Posted via] Interactive Networx Lines: 20 Message-ID: <8adp9r$4bn$1@unlisys.unlisys.net> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> <96A6D088EF5292BB.F33A600BA31A8CE7.EBC6A26177D83CB0@lp.airnews.net> <38cd56f2.9397381@news.freeuk.net> NNTP-Posting-Host: fubar.snafu.de x-no-archive: yes X-Newsreader: NN version 6.5.0 #3 (NOV) Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!newscore.univie.ac.at!194.25.134.126.MISMATCH!newsfeed01.sul.t-online.de!t-online.de!unlisys!news.snafu.de!wolfi Xref: chonsp.franklin.ch alt.folklore.computers:51645 greenaum@BOLLOCKSyahoo.co.uk writes: >What, so you could double the quality of any VHS picture by running it >through a time-base corrector? By tarting up the sync pulses a bit? Not quite double. You can cure some of the defects of the VHS system, but not all of them. What TBC will cure is the defects caused by the imprecise band transport, which result in the shaky picture VHS often presents. It will not cure the limited bandwidth (blurry picture). >Why don't they? Because TBCs are expensive, ans VHS machines are supposed to be cheap. There are expensive editing decks for VHS/SVHS which do have TBCs. Regards -- wolfi@techno.de + wolfi@snafu.de + http://www.snafu.de/~wolfi/ + IRC:wolfi you're sweet like da dadada dadada ###### From: Brian Inglis Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: Sat, 11 Mar 2000 09:16:41 -0700 Organization: Systematic Software Reply-To: Brian.dot.Inglis@SystematicSw.ab.ca Message-ID: References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> X-Newsreader: Forte Agent 1.7/32.534 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit NNTP-Posting-Host: 207.148.143.181 X-Original-NNTP-Posting-Host: 207.148.143.181 X-Trace: 11 Mar 2000 09:16:42 -0700, 207.148.143.181 Lines: 68 X-Original-NNTP-Posting-Host: 204.50.1.43 Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!news.maxwell.syr.edu!newspeer.monmouth.com!nntp.cadvision.com!news.cadvision.com!207.148.143.181 Xref: chonsp.franklin.ch alt.folklore.computers:51580 On Thu, 9 Mar 2000 20:55:58 +0200, "Simo Tuominen" wrote: > >"danny burstein" wrote in message >news:8a7cno$fvr$1@panix6.panix.com... >> In <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> Brian Inglis > writes: >> >>So how does the data capacity of these same videotapes keep >getting >> >>bigger? From 20 meg to 4 gig, man. VCRs have always had pretty >crap >> >>resolution haven't they? >> >> >Assuming mono encoding: >> >> >512 dot/line x 256 line/frame x 60 frame/s = 7.5Mb/s >> >> not quite. You're off by a factor of four... see below > >How come? What you're saying doesn't refute what he says. This is >theoretical. > >> >7.5Mb/s x 60s/m x 60m/h x 2h = 54kMb ~ 52Gb ~ 6.5GB Conversion from bits for rate to Bytes for capacity. >Um, Brian, exactly *why* did you change from the incorrect "b" to the >correct "B" in mid-conversion? > >> hmm, maybe a factor of two since you're saying 256 lines/frame >> rather than 525.. >> >> .. anyway.. >> >> standard (vhs) vcrs only record _one_ of the two fields out of >each >> frame, so you're only getting 262 lines (out of 525) of >> resolution. (usally actually a bit less since many don't even >bother with >> the overscan) > >Did you stop to consider that he might know this, and use 256 lines in >his calculation because of that? > >> (the fields alternate between the odd and even lines of the frame >every >> 1/60th of a second, meaning the complete frame is 1/30th of a >second) >> >> which means, btw, that the regular vcr (pretty much by definiton) >loses >> half of the original signal. (Actually, of course, it's worse than >that) > >Yep. A typical VCR records maybe 240 lines per two fields, so you lose >a lot. Of course, I only know about PAL VCRs, but the magnitude is >right. 512 bits per line is definitely too much anyway. 400 I'd >believe. Maybe. How would signal bandwidth limits impact a "mono" recording? If the signal was bandwidth limited, the rate would have to be decreased by a fudge factor of 2-4 to increase reliability. Thanks. Take care, Brian Inglis Calgary, Alberta, Canada -- Brian_Inglis@CSi.com (Brian dot Inglis at SystematicSw dot ab dot ca) use address above to reply ###### Sender: Ian Stirling From: Ian Stirling Subject: Re: field/frame, was: Re: video tape backup systems Newsgroups: alt.folklore.computers References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> <96A6D088EF5292BB.F33A600BA31A8CE7.EBC6A26177D83CB0@lp.airnews.net> <38cd56f2.9397381@news.freeuk.net> Organization: None.. User-Agent: tin/pre-1.4-980818 ("Laura") (UNIX) (Linux/2.2.13 (i586)) Lines: 20 Message-ID: X-Abuse-Info: Please be sure to forward a copy of ALL headers X-Abuse-Info: Otherwise we will be unable to process your complaint properly X-Complaints-To: admin@usenetserver.com NNTP-Posting-Date: Sat, 11 Mar 2000 11:56:53 EST Date: Sat, 11 Mar 2000 16:56:53 GMT Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!news.maxwell.syr.edu!cyclone1.usenetserver.com!cyclone1.usenetserver.com!news-west.usenetserver.com.POSTED!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:51665 greenaum@BOLLOCKSyahoo.co.uk wrote: >What, so you could double the quality of any VHS picture by running it >through a time-base corrector? By tarting up the sync pulses a bit? >Why don't they? It's not quite that simple for moving images. There are not 25/30 pictures per second, shown in two halves, but 50/60 per second, with half the scan lines. So, to do this well, you'd need a pretty good motion detection algorithm, and big heaps of CPU. Horizontal only motion estimation is rather easier. -- http://inquisitor.i.am/ | mailto:inquisitor@i.am | Ian Stirling. ---------------------------+-------------------------+-------------------------- Get off a shot FAST, this upsets him long enough to let you make your second shot perfect. -- Robert A Heinlein. ###### From: wolfi@berlin.snafu.de (Wolfgang Schwanke) Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: 17 Mar 2000 21:41:23 GMT Organization: [Posted via] Interactive Networx Lines: 24 Message-ID: <8au8q3$gg6$1@unlisys.unlisys.net> References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <8aafml$a4m$1@unlisys.unlisys.net> <8ai0v1$ogu@poseidon.rz.uni-duesseldorf.de> NNTP-Posting-Host: fubar.snafu.de x-no-archive: yes X-Newsreader: NN version 6.5.0 #3 (NOV) Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!naxos.belnet.be!news.belnet.be!newshub.bart.net!colt.net!news0.de.colt.net!newscore.gigabell.net!unlisys!news.snafu.de!wolfi Xref: chonsp.franklin.ch alt.folklore.computers:52150 Hello, "Simo Tuominen" writes: >"Wolfgang Schwanke" wrote in message >news:8aafml$a4m$1@unlisys.unlisys.net... >[snip] >> between the two, and has lead many people to believe that >> VCRs drop scan lines on purpose, which of course is a compolete >> misunderstanding. >I didn't say that the loss is based on some arbitrary decision. I know >very well that it just happens, because tecnology isn't perfect. I meant to say that VCRs don't drop scan lines at all. Regards -- wolfi@techno.de + wolfi@snafu.de + http://www.snafu.de/~wolfi/ + IRC:wolfi you're sweet like da dadada dadada ###### Sender: eric@ruckus.brouhaha.com From: Eric Smith Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> X-Disclaimer: Everything I write is false. Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy. Date: 19 Mar 2000 17:50:06 -0800 Message-ID: Lines: 24 X-Newsreader: Gnus v5.5/Emacs 20.3 NNTP-Posting-Host: ruckus.brouhaha.com X-Trace: 19 Mar 2000 10:31:07 -0800, ruckus.brouhaha.com Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!enews.sgi.com!news.sgi.com!news.spies.com!ruckus.brouhaha.com Xref: chonsp.franklin.ch alt.folklore.computers:52402 dannyb@panix.com (danny burstein) writes: > standard (vhs) vcrs only record _one_ of the two fields out of each > frame, so you're only getting 262 lines (out of 525) of > resolution. (usally actually a bit less since many don't even bother with > the overscan) [...] > which means, btw, that the regular vcr (pretty much by definiton) loses > half of the original signal. (Actually, of course, it's worse than that) False. As Rimmer would say, "completely brimming over with wrongability." VHS records both fields. Where on earth did you get the idea that it doesn't? Easy way to prove this: use the pause feature on a consumer Laserdisc player with a CAV laserdisc that was mastered from a film (not video) source, and has incorrect white flags. When you do that, you get field motion, because the player is interlacing two fields that don't belong together. Now record a minute of that to VHS. Play it back. If your claim was correct, you wouldn't get field motion in the playback, because the VHS recorder was throwing away half the fields. ###### Sender: eric@ruckus.brouhaha.com From: Eric Smith Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems References: <89v5an$ehl$1@freenet9.carleton.ca> <38C3F59B.1913@azstarnet.com> <38cb545f.6488407@news.freeuk.net> <9o6ecsgabhr97fdodsvhq2c5nj7t9eemks@4ax.com> <8a7cno$fvr$1@panix6.panix.com> <8aa6sa$p41@poseidon.rz.uni-duesseldorf.de> <38C8E324.99E24FE8@ic.ac.uk> X-Disclaimer: Everything I write is false. Organization: Eric Conspiracy Secret Labs X-Eric-Conspiracy: There is no conspiracy. Date: 19 Mar 2000 17:54:52 -0800 Message-ID: Lines: 25 X-Newsreader: Gnus v5.5/Emacs 20.3 NNTP-Posting-Host: ruckus.brouhaha.com X-Trace: 19 Mar 2000 10:35:54 -0800, ruckus.brouhaha.com Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!enews.sgi.com!news.sgi.com!news.spies.com!ruckus.brouhaha.com Xref: chonsp.franklin.ch alt.folklore.computers:52405 Simon writes: > VCRs record both fields of a video frame, so there is not a huge amount > of data loss from line reduction. The only thing that is lost is the > interlace signal, so whereas normal TV is 480/580* lines (approx) at > 30/25 Hz frame rate, VHS pictures are approx. 240/290* lines at > 60/50 Hz frame rate. If I understand correctly SVHS preserves the > interlace pulses. Neither VHS nor SVHS records the "interlace pulses" to tape. But both generate a standard NTSC interlaced signal on playback, with the fields interlaced into frames exactly as they were when recorded. It is possible to record a non-interlaced signal (with timing that is otherwise close to NTSC) onto a VHS VCR. When played back, you get an interlaced signal. > *I don't have the exact figures to hand for the number of picture lines > in a frame - but it's something around this. There are 20, 20.5, or 21 lines of blanking interval per field, depending on whether it's an odd or even field, and whether closed captioning is used, so the active video lines per frame are between 483 and 484.5. Of course, some of those active video lines are outside the safe area, and will not be seen on a normally-adjusted consumer television due to the overscan. ###### From: dannyb@panix.com (danny burstein) Newsgroups: alt.folklore.computers Subject: Re: field/frame, was: Re: video tape backup systems Date: 19 Mar 2000 22:10:13 -0500 Organization: PANIX Public Access Internet and UNIX, NYC Lines: 17 Message-ID: <8b44ql$19d$1@panix5.panix.com> References: <8a7cno$fvr$1@panix6.panix.com> NNTP-Posting-Host: panix5.panix.com X-Trace: news.panix.com 953521814 14464 166.84.0.230 (20 Mar 2000 03:10:14 GMT) X-Complaints-To: abuse@panix.com NNTP-Posting-Date: 20 Mar 2000 03:10:14 GMT X-Newsreader: NN version 6.5.1 (NOV) Path: chonsp.franklin.ch!pfaff.ethz.ch!news-zh.switch.ch!news-ge.switch.ch!newsfeeds.belnet.be!news.belnet.be!news-raspail.gip.net!news-peer.gip.net!news.gsl.net!gip.net!howland.erols.net!panix!news.panix.com!panix5.panix.com!not-for-mail Xref: chonsp.franklin.ch alt.folklore.computers:52351 In Eric Smith writes: >False. As Rimmer would say, "completely brimming over with wrongability." >VHS records both fields. Where on earth did you get the idea that it >doesn't? I'm checking further into this.. Panasonic made a big deal over a new VHS unit of theirs a couple of years ago and specifically stated in taht advert that full frame recording made this unit better than regular ones. I'll see what I can dig up. It's possible that they were misleading (nahhh...) or I may have misunderstood it.. -- _____________________________________________________ Knowledge may be power, but communications is the key dannyb@panix.com [to foil spammers, my address has been double rot-13 encoded]