VideoHelp Forum
+ Reply to Thread
Results 1 to 12 of 12
Thread
  1. I want to record on the vhs tape a test pattern that i downloaded and that I see many are using to establish the stabilization of a picture from vcr to capture device ( vhs or dvd recorder tbc efficiency ).
    My pc has only dvi and hdmi outputs but i can use the old laptop to output tv signal trough svideo to vcr svideo input.
    So my question is so this can be effective i just open the file in the mean time the vcr is recording full screen from laptop and the pattern is on the tape right?

    1. Should i use old tape to do so or even new is ok ?
    2. will the vcr ( in this case high end panasonic svhs ) be better or some bad regular vcr so to exaggerate the symptoms?
    3. is it posible that there no tbc errors while recording from perfect still of a pc and on good vcr?

    Any other suggestions to do this ?
    Attached Thumbnails Click image for larger version

Name:	reswedge.png
Views:	377
Size:	118.3 KB
ID:	11914  

    Quote Quote  
  2. I usually record test patterns onto a DVD then record onto VHS from the DVD player. If you have any THX certified DVDs you might be able to use the calibration videos from those.
    Quote Quote  
  3. I usually record test patterns onto a DVD then record onto VHS from the DVD player. If you have any THX certified DVDs you might be able to use the calibration videos from those.
    Thanks jagabo i dont think i have thx certified dvd's how to know if there are i have maybe 20 bought dvd's but im not sure where to see that they are thx certified i have saround sound that is thx certified and sound card that is also, is there some cd that came with them that i can use.

    Also the original file is pdf i made it png you suggest i just author png to dvd using authoring works or similar and play on dvd recorder and then output to vcr right? that seems simple

    what about the vcr and the tape are they ok is new gona fit or better to use some old problematic tape and vcr
    Quote Quote  
  4. Member edDV's Avatar
    Join Date: Mar 2004
    Location: Northern California, USA
    Search Comp PM
    THX DVD list (contains THX optimizer)
    http://www.thx.com/consumer/home-entertainment/thx-certified-releases/

    When you record a stable test signal to VHS, the servos are locked to stable sync but there is still some timebase jitter due to mechanical tolerance (similar to audio recorder flutter and wow). Playback has greater timebase error as the servos attempt to lock to unstable h sync with significant jitter.
    Last edited by edDV; 12th Apr 2012 at 11:59.
    Recommends: Kiva.org - Loans that change lives.
    http://www.kiva.org/about
    Quote Quote  
  5. Thanks what resolution do you suggest i tried tiff but mu dvd recorder didn't recognize it trough sd reader i will try jpeg is it better 720x576 the same as the dvd or bigger is better
    Quote Quote  
  6. Member edDV's Avatar
    Join Date: Mar 2004
    Location: Northern California, USA
    Search Comp PM
    Originally Posted by mammo1789 View Post
    Thanks what resolution do you suggest i tried tiff but mu dvd recorder didn't recognize it trough sd reader i will try jpeg is it better 720x576 the same as the dvd or bigger is better
    If you output first to DVD, encode 720x480 (that is 480 height with side filler out to720*). That way you avoid the rescaler in your computer display card. The DVD player will convert that to analog Y at 480i with horizontal bandwidth in the 5 MHz range. The VHS deck will low pass filter this to ~ 3MHz VHS (or 4.5 MHz SVHS) before FM encoding to RF for recording to tape.


    * keep the same aspect ratio for the chart.
    Recommends: Kiva.org - Loans that change lives.
    http://www.kiva.org/about
    Quote Quote  
  7. i don't understand why the picture cannot be read by the dvd

    i found this pdf file it has very big resolution i can keep the aspect ratio because that way i don't resize to 720x576 it will go to 720 x983 is there some ts file like this sequence i can download from internet and just play it on dvd i couldn't find one

    all my dvd recorders say unsupported I never put pictures on dvd recorder so is is something I should know i use pc for pictures i use cdr-w
    Attached Files
    Last edited by mammo1789; 12th Apr 2012 at 14:16.
    Quote Quote  
  8. Member edDV's Avatar
    Join Date: Mar 2004
    Location: Northern California, USA
    Search Comp PM
    I made a first pass effort.

    I took the 2550x3300 Wedge chart and imported to Vegas. Then created a ramp test signal in Vegas media generator and composited the Wedge chart over it. Vegas downscaled the Wedge chart to 576 vertcal and scaled horizontal for 4:3 PAL. Then I used the levels filter to set chart black to 16 and chart white to 235.

    Click image for larger version

Name:	Wedge_Vegas_Create.png
Views:	69
Size:	141.3 KB
ID:	11917

    Then I exported the chart composite as a still and encoded to PAL DVD MPeg2.

    Name:  Wedge720x576.png
Views: 93
Size:  67.2 KB

    PAL DVD MPeg2 720x576
    Attached Files
    Last edited by edDV; 12th Apr 2012 at 15:18.
    Recommends: Kiva.org - Loans that change lives.
    http://www.kiva.org/about
    Quote Quote  
  9. Attached is the test pattern video used in this thread:
    http://forum.videohelp.com/threads/232830-Test-of-various-VCRs-Image-Quality-from-VHS-...%28Big-Pics%29
    Attached Files
    Quote Quote  
  10. I took the 2550x3300 Wedge chart and imported to Vegas. Then created a ramp test signal in Vegas media generator and composited the Wedge chart over it. Vegas downscaled the Wedge chart to 576 vertcal and scaled horizontal for 4:3 PAL. Then I used the levels filter to set chart black to 16 and chart white to 235.
    Thanks edv but when i play the mpeg file on dvd it is not full screen ( no mater what aspect i put on the player ) and when i record on the vcr it has some short black streaks ( is the recording head dirty or damaged ) I haven't tried to record on the vhs long time ago only play it so i will try from tv signal to see if the same.

    Why did you say it is important to keep aspect ratio i will try to make the picture and make it video in vdub duration 1 min
    To me with or without tbc the picture is stable the lines are not waving like on the other treads I saw on the forum
    Quote Quote  
  11. If you're only concerned about jitter from time base errors you don't really care about aspect ratios or the picture filling the screen. All you really need is straight vertical lines so you can see the jitter.
    Quote Quote  
  12. Member edDV's Avatar
    Join Date: Mar 2004
    Location: Northern California, USA
    Search Comp PM
    Originally Posted by jagabo View Post
    If you're only concerned about jitter from time base errors you don't really care about aspect ratios or the picture filling the screen. All you really need is straight vertical lines so you can see the jitter.
    Right. Aspect ratio is only important for using the chart to measure luma frequency roll off. At some point the wedges will merge to gray in bandwidth limited formats like VHS which low pass filters luma at 3 MHz. SVHS low pass filters luma at ~4.5 MHz. DVD has a Nyquist limit of 6.75 MHz but typical players limit analog out to ~5.5MHz.

    For timebase error measurement, you measure the extent of horizontal line offset (line to line offset).

    This chart has large areas of 235 white which are difficult to reproduce in FM modulated VHS players. A better chart would use a medium gray background with full white to black wedges.
    Recommends: Kiva.org - Loans that change lives.
    http://www.kiva.org/about
    Quote Quote  



Similar Threads