LASERDISC vs VCD

[AwesomeDude]

What are the differences between a VCD and a laserdisc?

[canadateck]

VCD




Laserdisc

[dphirschler]

I was going to point you to the glossary, but I just checked and "laserdisc" is not there.


Darryl

[Cornucopia]

I hate to break it to you but what you have there isn't VCD (as in WhiteBook VideoCD), it's CDV (as in CompactDisc+Video). CDV is a hybrid CD format combining standard AudioCD with Laserdisc video. It is pressed similarly to the way an Enhanced (Multisession) Audio CD would be.

Again:

VCD is Digital Video based on MPEG1, using CDXA bridge disc.
CDV is split hybrid disc with Digital Audio on 1st part, 2nd part is Frequency Modulated Analog Signal.

Scott

[canadateck]

Are you talking about the Pictures?I was just using them to show the diff in Size.

Laser Disc Big
VCD Small.
He wasnt clear in what he wanted to know.

[AwesomeDude]

You're right canadateck, I wasn't clear on what I wanted to know.
What I really wanted to know is what compression system is used for the video on a laserdisc and if videoCD is based on laserdisc or not. Thanks

[tedkunich]

What I really wanted to know is what compression system is used for the video on a laserdisc and if videoCD is based on laserdisc or not. Thanks

Laserdiscs do not use any compression on the video as it is stored in analog form (think of it as PCM for video). The audio may or may not use compression - the standard allows for 2 analog track and 2 digital (ala CD but at 48kHz) tracks. Some later discs used compressed AC3 and DTS on the digital tracks.

[OmegaSupreme]

From http://www.dvddemystified.com
How does DVD compare to laserdisc?

Features: DVD has the same basic features as CLV LD (scan, pause, search) and CAV LD (freeze, slow) and adds branching, multiple camera angles, parental control, video menus, interactivity, etc., although some of these features are not available on all discs.

Capacity: Single-layer DVD holds over 2 hours, dual-layer holds over 4 hours. CLV LD holds one hour per side, CAV holds half an hour. A CAV laserdisc can hold 104,000 still images. DVD can hold thousands of still pictures accompanied by hundreds of hours of audio and text.

Convenience: An entire movie fits on one side of a DVD, so there's no need to flip the disc or wait for the player to do it. DVDs are smaller and easier to handle. DVD players can be portable, similar to CD players. Discs can be easily and cheaply sent through the mail. On the other hand, laserdiscs have larger covers for better art and text.

Noise: Most LD players make a whirring noise that can be heard during quiet segments of a movie. Most DVD players are as quiet as CD players.

Audio: LD can have better quality on Dolby Surround soundtracks stored in uncompressed PCM format. DVD has better quality on Dolby Digital or music only (PCM). LD has 2 audio tracks: analog and digital, whereas DVD has up to 8 audio tracks. LD uses PCM audio sampled with 16 bits at 44.1 kHz. DVD LPCM audio can use 16, 20, or 24 bit samples at 48 or 96 kHz (although PCM is not used with most movies). LD has surround audio in Dolby Surround, Dolby Digital (AC-3), and DTS formats. 5.1-channel surround sound is available by using one channel of the analog track for AC-3 or both channels of the digital track for DTS. DVD uses the same Dolby Digital surround sound, usually at a higher data rate of 448 kbps, and can optionally include DTS (at data rates up to 1536 kbps compared to LD's 1411 kbps, but in practice DTS data rates are often 768 kbps). DVD players convert Dolby Digital to Dolby Surround. The downmixing, combined with the effects of compression, often results in lower-quality sound than from LD Dolby Surround tracks.

Video: DVD usually has better video. LD suffers from degradation inherent in analog storage and in the composite NTSC or PAL video signal. DVD uses digital video, and even though it's heavily compressed, most professionals agree that when properly and carefully encoded it's virtually indistinguishable from studio masters. This doesn't mean that the video quality of DVD is always better than LD. Only that it can be better. Also keep in mind that the average television is of insufficient quality to show much difference between LD and DVD. Home theater systems or HDTVs are needed to take full advantage of the improved quality.

Resolution: In numerical terms DVD has 345,600 pixels (720x480), which is 1.3 times LD's approximately 272,160 pixels (567x480). Widescreen DVD has 1.7 times the pixels of letterboxed LD (or 1.3 times anamorphic LD). As for lines of horizontal resolution, DVD has about 500 whereas LD has about 425 (more info in 3.4.1). In analog output signal terms, typical luma frequency response maintains full amplitude to between 5.0 and 5.5 MHz. This is below the 6.75 MHz native frequency of the MPEG-2 digital signal. Chroma frequency response is one-half that of luma. Laserdisc frequency response usually begins to fall off at 3 MHz. (All figures are for NTSC, not PAL.)
Legacy titles: Some movies on laserdisc will probably never appear on DVD (see Julien Wilk's Laserdisc Database).

Availability: DVD players and discs are available for purchase and rental in thousands of outlets and on the Internet. LD players and discs are becoming hard to find.
Price: Low-cost DVD players are cheaper than the cheapest LD player. Most movies on DVD cost less than on LD.

Restrictions: For those outside the US, regional coding (see 1.10) is a definite drawback of DVD. For some people Macrovision copy protection (see 1.11) is an annoyance. Laserdisc has no copy protection and does not have regional differences other than PAL vs. NTSC.

Recordable: DVD recorders are increasingly affordable. Laserdisc recording, at a low of $250 per disc, was never available to general consumers.

[Cornucopia]

LD doesn't "compress" its signal, nor does it digitally encode it's carrier. Think of LD as an Audio LP on steroids. The optical "groove" is a solid continuous hill-and-dale spiral, not pits-and-lands like CD/DVD. If you took a broadcast TV signal, like the kind you would see on a waveform monitor, and FM-modulated it like an RF converter box would do, that would be the signal you could "see" if you unwound the LD optical spiral.

Therefore:
the ONLY way to get a 1st generation LD video signal into a computer and onto a DVD or VCD is to play it with an LD player while digitizing it with a DVD/VCD recorder or capture card.

BTW, IIRC the audio track is in it's usual place as an intermediate frequency carrier in the RF spectrum--even if the signal was supposed to be a "Digital Track".

HTH,
Scott

[edDV]

"Resolution: In numerical terms DVD has 345,600 pixels (720x480), which is 1.3 times LD's approximately 272,160 pixels (567x480). Widescreen DVD has 1.7 times the pixels of letterboxed LD (or 1.3 times anamorphic LD). As for lines of horizontal resolution, DVD has about 500 whereas LD has about 425 (more info in 3.4.1). In analog output signal terms, typical luma frequency response maintains full amplitude to between 5.0 and 5.5 MHz. This is below the 6.75 MHz native frequency of the MPEG-2 digital signal. Chroma frequency response is one-half that of luma. Laserdisc frequency response usually begins to fall off at 3 MHz. (All figures are for NTSC, not PAL.) "

There are alot of apples (analog specs) being compared to oranges (digital specs) in that paragraph. Where to start?

First: "345,600 pixels (720x480), which is 1.3 times LD's approximately 272,160 pixels (567x480)"
This is an attempt to describe laserdisc resolution in digital pixel terms. The 567 number is a bit strange and must have been derived from some test to resolve lines from a test slide using a variable sample rate and filter tricks. It has little to do with what a capture card would deliver.

Second: "As for lines of horizontal resolution, DVD has about 500 whereas LD has about 425"
This is the way analog sources are usually compared while looking at the same test pattern from the two sources. "lines of horizontal resolution" is an eyeball determined figure when looking at a reference TV monitor and has nothing to do with horzontal pixels.

Third: "In analog output signal terms, typical luma frequency response maintains full amplitude to between 5.0 and 5.5 MHz. This is below the 6.75 MHz native frequency of the MPEG-2 digital signal."
This is an attempt to describe a DVD in analog terms for luminance frequency response. 6.75 MHz an is over an optimistic and not a realistic number. 6.75 MHz is half the 13.5 MHz sample rate (aka Nyquist frequency) which describes the theoretical maximum frequency response with a perfect anitaliasing filter at the A/D. Real world filtering reduces this number to 5.5 to 6.0 MHz on both the A/D an D/A side.

Forth: "Chroma frequency response is one-half that of luma."
This refers to the 4:2:2 sample scheme for DVD where R-Y and B-Y are sampled at 6.75 MHz (3.3 MHz Nyquist and 2.5 to 3 MHz realistic max)

Fifth: "(Chroma) Laserdisc frequency response usually begins to fall off at 3 MHz."
Actually NTSC encodes chroma by modulating a 3.58 MHz (4.43MHz PAL) subcarrier. Chroma is extracted with a comb filter and decoded back to R-Y and B-Y with maximum bandwidths in the 1.5-2.0 MHz range.


Bottom Line: Both are very close in luminance bandwidth for analog output. DVD is capable of superior chroma bandwith but the real differences are in noise, and luminance to chrominance distortions which are not discussed.

- DVD is capable delivering a higher signal to noise ratio

- Laserdisc is encoded as high quality NTSC or PAL. As such it suffers the normal luma to chroma and chroma to luma distortions inherent in composite video.

- DVD is encoded in component Y, Cb, Cr and suffers none of the cross color problems of NTSC or PAL when component outputs are used to the TV.

- DVD goes a step further for frame based original material (like film or computer animation) in that it can output in a progressive 60/frames per second 480p format for display on a progressive (EDTV or HDTV) monitor

[edDV]

What are the differences between a VCD and a laserdisc?

Def VCD = https://www.videohelp.com/vcd

Def of Laserdisc = http://www.oz.net/blam/LaserDisc/FAQ/

Def VideoCD (aka CD-I) = 6.2 in the above FAQ
http://www.oz.net/blam/LaserDisc/FAQ/FAQ_intro.htm#RivalsCD-I