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Old 24th June 2014, 01:16   #1  |  Link
AVCHDfreak
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U-matic anyone? Help needed for simulating dropouts and artifacts

Hi all,
Anybody here happen to be a user of U-matic decks (or even Betacam/[SP])? I'm trying to replicate old-school analog dropout artifacts and need help on defining the characteristics of them and maybe with making the script too. I'm after the "comet tail" white/black flickering streaks (also known as bearding) as well as the "cloned lines" artifact (kind of like using pointresize in Avisynth) where good lines are repeated while reading damaged parts of the tape (TBC error?).

Thanks in advance,
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Old 24th June 2014, 07:53   #2  |  Link
smok3
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U-matic deck was last seen more than 10 years ago, I still have a combined digibeta/SP deck, but there is an apparent lack of sp tapes (sd things that still come are usually imx or digibeta).
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Old 24th June 2014, 14:42   #3  |  Link
johnmeyer
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I may have the original from a 1968 Chicago NBC broadcast. It was a 2" Quadruplex --> Beta SP --> DVD transfer that contained significant dropouts. I'm not sure which of the two analog stages contributed the most. I could chop 30 seconds from the original and send post it, if you want. It is in MPEG-2 format.
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Old 24th June 2014, 20:10   #4  |  Link
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quadroplex should be 4 vertical stripes not in exact harmony (representing 4 heads) and some grainy/pixelated drops.

beta sp should be either grey drops or repeated lines.
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Old 24th June 2014, 20:29   #5  |  Link
raffriff42
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There are examples of U-Matic artifacts on YouTube. Start here and follow the related links.

There is a script to create a VHS effect here on YouTube which may interest you (since VHS and 3/4" artifacts are somewhat related).

Quote:
Originally Posted by AVCHDfreak View Post
I'm after the "comet tail" white/black flickering streaks (also known as bearding)
If I understand your description correctly, these could be faked by finding some black footage with white artifacts and overlaying it on your footage. (EDIT see my next post for possible implementation)

Quote:
Originally Posted by AVCHDfreak View Post
I'm after ... the "cloned lines" artifact... where good lines are repeated while reading damaged parts of the tape (TBC error?)
You can create or find a "mask" video (with occasional white lines over black) and use it to key [use as a mask for an overlay of] your footage with a 1- or 2-line vertical shift. (EDIT see my next post for possible implementation)

Last edited by raffriff42; 27th June 2014 at 21:11. Reason: edit
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Old 24th June 2014, 20:40   #6  |  Link
johnmeyer
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Here's one frame from the original video as I received it on a non-commercial DVD, showing a typical dropout (the actor is Mandy Patinkin, while he was still in high school):



Here is a link to a few seconds from the un-modified original MPEG-2 file, showing a portion of the video with a fairly large number of droupouts:

1968 Video

I re-mastered the entire productions, using AVISynth to reduce noise & remove dropouts. I then used Vegas to correct color, adjust gamma, add chapters, correct rolling video, and more.

Hope this helps!

P.S. This is not a commercial DVD, and I believe was created by someone at the station for the performers involved.

[edit] I should also add that I actually do not know the chain of transfer from what was obviously (because of the date) Quadruplex 2" tape to the DVD that I received. I only guessed that it was converted to Beta SP and then to DVD.

Last edited by johnmeyer; 24th June 2014 at 20:42. Reason: Added second postscript
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Old 25th June 2014, 05:11   #7  |  Link
raffriff42
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Quote:
Originally Posted by raffriff42 View Post
I can't think of an Avisynth way to generate such sparse random lines.
I did think of a hackish way to do it...
Code:
## Last=something
return glitchmask(fullwidth=true, rarity=6)

##################################
### generate random glitches (white on black)
##
## @ fullwidth - if true, glitch is full picture width;
##          if false, glitch is random width & location
##
## @ rarity - higher values give fewer glitches 
##
## memory leak? (EDIT or merely consume lots of cache memory)
##
function glitchmask(clip C, bool "fullwidth", int "rarity")
{
    fullwidth = Default(fullwidth, false)
    global gm_rty = Min(Max(1, Default(rarity, 1)), 32768)

    BG = C.Levels(0, 1.0, 255, 0, 0, coring=false).ConvertToRGB32

    ## line glitch (full picture width)
    M1 = ScriptClip(BG, """
      drawboxmask(x=0, y=Rand(Height*gm_rty), wid=Width, hgt=1)
    """)

    ## random glitch (1 to 8 pix wide)
    M2 = ScriptClip(BG, """
      drawboxmask(x=Rand(Width), y=Rand(Height*gm_rty), wid=Rand(8), hgt=1)
    """)

    M = (fullwidth) ? M1 : M2
    return M.ConvertToY8.ConvertToYV12
    \    .ColorYUV(levels="TV->PC")
}

##################################
### draw a white box on black background
##
## @ clip C - assumed black clip
##
function drawboxmask(clip C, 
\    int "x", int "y",
\    int "wid", int "hgt")  
{
    x2    = Min(Max(0, Default(x, 0)), C.Width)
    y2    = Min(Max(0, Default(y, 0)), C.Height)
    wid   = Max(1, Default(wid, 0))
    hgt   = Max(1, Default(hgt, 0))
    wid   = Min(wid, C.Width-x2)
    hgt   = Min(hgt, C.Height-y2)

    box = C.Crop(0, 0, wid, hgt).Invert

    return (wid<=0||hgt<=0||x<0||x>=C.Width||y<0||y>=C.Height) ? C 
    \ : Layer(C, box.ResetMask, "add", 257, x2, y2, use_chroma=false)
}

Last edited by raffriff42; 11th November 2014 at 00:26. Reason: memory
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Old 25th June 2014, 07:52   #8  |  Link
smok3
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@johnmeyer, nice, I belive those are qoadroplex drops.
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Old 27th June 2014, 20:38   #9  |  Link
Alex-Kid
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There was a movie filmed in U-matic last year: NO (Chile) Movie Trailer (available in 720p). Hope it helps.
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Old 13th August 2014, 23:23   #10  |  Link
AVCHDfreak
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Been away for a while, anyway thanks for all the replies!
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Old 14th August 2014, 06:22   #11  |  Link
jmac698
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I wrote one a long time ago
http://forum.doom9.org/showthread.ph...67#post1470667
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Old 14th August 2014, 09:21   #12  |  Link
smok3
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Quote:
Originally Posted by Alex-Kid View Post
There was a movie filmed in U-matic last year: NO (Chile) Movie Trailer (available in 720p). Hope it helps.
Nice, that looks like one of the must-see movies.
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Old 22nd August 2014, 03:17   #13  |  Link
AVCHDfreak
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Thanks for sharing your script jmac698.
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