Q: Sound and Vision Q&A. Correct info about VHS vs. SVHS?

Discussion in 'Archived Threads 2001-2004' started by Steve Owen, Jun 15, 2002.

  1. Steve Owen

    Steve Owen Second Unit

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    The July/August Sound and Vision just came in the mail. In the Q&A section (Ian Masters), someone asked a question about S-VHS. The gist of the question was he's using the composite input fed from a satellite receiver into the S-VHS VCR. He tried the S-video connection, but preferred the results using the composite.
    Mr. Masters response...
     
  2. AaronD

    AaronD Stunt Coordinator

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    I'm pretty sure he's wrong. I've seen noticable (read: HUGE) improvements recording from composite devices with an SVHS VCR. To my knowledge the only difference is that the VCR's comb filter is used instead of the comb filter on the source device.

    -Aaron
     
  3. Rachael B

    Rachael B Producer

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    It's not a good answer because even if you use S-VHS using composite connections you get more lines of resolution. How much colour you might lose will be a function of how good the comb filters are that your signal is going into. Furthermore, some satelite boxes look better played out their composite into better Y/C conversion elsewhere in the signal chain. The answer is all wet![​IMG]
     
  4. Steve Owen

    Steve Owen Second Unit

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    That's what I thought. I can't tell you how many times I've seen blatantly incorrect information given in that column. The guy really has no business writing an audio/video advise column as far as I'm concerned.

    -Steve
     
  5. RoyGBiv

    RoyGBiv Stunt Coordinator

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    I have two S-VHS VCRs connected to one DirecTV receiver, and since the receiver has only one s-video output, the second VCR is connected via composite. There is no question that the picture is significantly better with composite to S-VHS than composite to regular VHS. In fact, I can often not see the difference between the VCR receiving the s-video signal and the one receiving the composite signal. There is a theoretical advantage to using s-video out to an S-VHS VCR because supposedly the DirecTV signal is sent with separate chrominance/luminance signals. Therefore, you should be eliminating the conversion to composite at the receiver and separate conversion back to s-video at the VCR. I don't think it has anything to do with which has a better comb filter in this case (unlike which input into the TV is better).

    SMK
     
  6. Steve Owen

    Steve Owen Second Unit

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  7. David Ison

    David Ison Stunt Coordinator

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    you can get no more lines of resolution than what is being fed to s-vhs from a composite vhs (245- 250 lines ), the only benefit might be from better noise(video) reduction on a newer s-vhs vcr. as far as sep. of crom. from lum. goes , the comb filters in the display device could also account for a somewhat better picture, easier to do when separated.
     
  8. David Ison

    David Ison Stunt Coordinator

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    FIRST OF ALL SORRY ABOUT THE POSTS BACK TO BACK. when you record in S-VHS it is possible to get 420 lines of res. ,but when you send 250 lines of res. you get 250 Lines recorded onto 420 lines not more resolution, like pouring 2 gals. into a 5gal. jug, yeah it will hold it but you don't get 5 gals. just by putting it in the bigger(in this case a better recorder)CONTAINER.
     
  9. Allan Jayne

    Allan Jayne Cinematographer

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    The satellite TV signal probably has 330 lines of resolution if it was not overly compressed. If so, S-VHS via composite will record it all but regular VHS via S-video (if available) won't. Both composite and S-video feeds to the VCR or TV can carry upwards of 540 lines subject to the quality of the equipment. Both regular VHS and S-VHS record only about 30 lines of chroma resolution. Both regular and S-VHS are subject to wow and flutter and time base errors from a poor quality VCR mechanism. To be assured of S-VHS quality you must use S-VHS grade tape. Some regulr tapes may work but that is unpredictable.
    The primary reason why composite from the stellite TV tuner may give better results is if the comb filter in the tuner box (required for analog channels) is not as good as that in the VCR or TV. Using the S-video output is alwys better for digitl (I don't mean digitized analog) chsannels.
    Video hints:
    http://members.aol.com/ajaynejr/video.htm
     
  10. StephenMSmith

    StephenMSmith Stunt Coordinator

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    When you say "analog channels" do you mean cable/air channels tuned in through the ANT IN coax? And by "digital channels" you mean DirectTV?

    Steve
     
  11. Steve Owen

    Steve Owen Second Unit

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    In looking into this issue further, I discovered something interesting that may have caused Mr. Ian Masters of Sound & Vision to answer the way he did...

    Apparently there are some (cheap) SVHS VCRs out there that don't even have a comb filter and thus they resuse to record in SVHS mode unless the signal is coming in the S-video line. There are other, nearly as cheap, SVHS VCRs that don't have a comb filter, but instead just throw in a low-pass filter on the composite line that cuts off all the luminance above 3 MHz thus rendering the signal no better than standard VHS.

    So, it turns out that in -some- instances, his answer was correct (though, IMO, it was still -mostly- incorrect). My apologies.

    -Steve
     
  12. Allan Jayne

    Allan Jayne Cinematographer

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    RE: Analog channels

    Cable TV, and I believe also satellite systems and Direct TV, have 6 Mhz channels like over the air TV. In a channel a station's signal can be (1) regular analog, (2) digitized analog, or (3) digital. In the first two cases the video is natively composite and needs a comb filter to extract more than about 240 lines of luminance resolution. They may or may not be converted to S-video or component video in the cable box. Category 1 signals look just like over the air NTSC (or PAL) broadcasts when fed into a TV's antenna jack. For a regular cable box or cable ready TV, assuming the frequency definitions of the channels according to the box match what is coming over the cable, only category 1 is usable and in the case of a cable ready TV only the unscrambled ones are usable and in the case of a non-cable ready TV with no cable box only channels 2 - 13 are usable. The digital cable or Direct TV box converts category 2 signals into any or all of category 1, composite, S-video or component. HDTV requires category 3. Category 3 signals over cable or Direct TV do not necessarily resemble ATSC DTV/HDTV broadcasts. Category 3 signals are natively Y/Pb/Pr component video and are usually also offered as (converted to) S-video or composite by the cable or direct TV box.
     
  13. Wayne A. Pflughaupt

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    I thought it should be mentioned: In this month’s Sound and Vision, p. 24 notes that the abovementioned questionable statement about S-VHS resolution using composite vs. S-video connections was added in the magazine’s editing process.
    “Q&A” columnist Ian G. Masters was not responsible for the erroneous information.
    Personally I’ve generally found his advice to be quite good. He’s published and answered a few of my own questions in the past.
    Regards,
    Wayne A. Pflughaupt
     

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