1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

converting to anamorphic (?)

Discussion in 'Desktop & Laptop Computers Forum' started by figrin_dan, Feb 11, 2003.

  1. figrin_dan

    figrin_dan
    Active Member

    Joined:
    Jan 9, 2003
    Messages:
    1,993
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Ratings:
    +135
    I have a few Hi8/Video8 cassettes which I would like to transfer to dvdr. They are all recorded in letterbox (ie Not anamorphic). Is there any software that will convert to anamorphic, in theory giving me a clearer picture.
    Cheers
     
  2. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,788
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    The MPEG encoder - TMPGENC - will do this. You have to do some calculation to work out the correct 'new shape' for your image.

    BUT: It won't (can't) improve the quality of the image from what you already have.
     
  3. figrin_dan

    figrin_dan
    Active Member

    Joined:
    Jan 9, 2003
    Messages:
    1,993
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Ratings:
    +135
    Thanks for the info.

    Do you know if this 'adds lines' or stretches the picture. Surely if lines are added, even just repeating every other line or so, the picture in anamorphic would improve on the picture in zoomed mode?
     
  4. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,788
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    Not sure exactly how it does what it does. My guess is that it recalculates and interpolates pixels to the new horizontal structure (more lines). But, I say again, if the 'information' isn't there in the first place (on the tape) the best it can do is interpolate - which doesn't actually generate any more information - it just can't, if it's not there to start with. More information = more detail.
     
  5. figrin_dan

    figrin_dan
    Active Member

    Joined:
    Jan 9, 2003
    Messages:
    1,993
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Ratings:
    +135
    heheh, I like the sound of that!
    Is this what the zoom mode on my (WS) TV does? If it does then I think I understand . . .
     
  6. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,788
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    If it's a CRT TV, then no.

    TV signals are made up of horizontal scan lines. CRT TVs show these lines exactly, 1 for 1. 'Zoom' alters the properties of the magnets around the neck of the tube so as to increase the height of the picture by simply displaying the lines further apart.

    This is quite different to the 'scaling' techniques used in LCD and Plasma devices, where the scan line structure is recalculated and re-mapped onto the FIXED array of pixels that the screen consists of. For example, most standard plasmas have 480 rows of pixels. Whereas a PAL TV picture has 576 scan lines in it. These 576 lines have to be 'mapped' onto the 480 rows of pixels and it clearly can't be done, 1 for 1. Which is where the scaler comes in.

    My guess is that TMPGENC uses similar scaling techniques to recalculate the contents of each pixel in the digital signal which is also a fixed array of pixels. (For MPEG2 as used on DVDs, the digital picture is 704 (W)*576 (H) pixels). If you have a source (such as yours) which uses only the central part of the available 576 lines - 432 lines or thereabouts - then, in order to refit this into 576 lines (ie - use all the the available height - which makes the image anamorphic) you'd need to 'scale' the 432 up to 576. And this is done by recalculating the value for each row of pixels.

    But - it doesn't (can't) ADD anything back into the signal, that wasn't there to start with.
     
  7. Squirrel God

    Squirrel God
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    While true of basic CRTs, I thought technologies like Sony's DRC filled in the gaps between the lines on zoomed images via interpolation. :confused:
     
  8. LV426

    LV426
    Administrator Staff Member

    Joined:
    Jul 14, 2000
    Messages:
    12,788
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Somewhere in South Yorkshire
    Ratings:
    +4,975
    TVs with line-doubling techniques (like DRC) create twice as many lines for the display by interpolating. Yes. But, again, when zoomed, all they do is display the (twice as many) lines further apart.
     
  9. Rob.Screene

    Rob.Screene
    Active Member

    Joined:
    Sep 29, 2001
    Messages:
    1,124
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Berks, England
    Ratings:
    +45
    I have used TMPGenc's resize and AVIsynth's trio of resize algorithms. To convert to anamorphic you need to crop the top and bottom and resize to 1.3333333333x on the vertical.

    On a picture that you viewing by a scaler anyway (or HTPC), there may be a very slight LOSS of vertical detail because you are doing the rescale twice and the first time is not an ideal multiple.

    Surprisingly, 16:9 "pre-scaled anamorphic" widscreen DVD-R looks much, much better than a zoomed letterboxed picture on my 32 inch telly.

    I think this is because in TV zoomed modes the scanlines have noticeable gaps between them, making the picture look a little coarse, also because the scaling algorithms available at encoding time now are brilliant, such as BilinearResize() or LanczosResize() http://www.avisynth.org/index.php?page=Resize

    The real ideal for me is to have a PAL 4:3 source, crop to to 480p, drop the frame rate to the correct 23.97<mumble>fps and resize it horzontally down to about 680, giving a true anamorphic ntsc laserdisc with no horizontal overscan.

    regards,
    Rob.

    regards,
    Rob.
     
  10. figrin_dan

    figrin_dan
    Active Member

    Joined:
    Jan 9, 2003
    Messages:
    1,993
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    66
    Ratings:
    +135
    This is what I was thinking about when I thought it may look better, not actually more info but less gaps of nothing.

    Are you converting ntsc laserdiscs to anamorphic dvdr? How do they come out?
     
  11. Rob.Screene

    Rob.Screene
    Active Member

    Joined:
    Sep 29, 2001
    Messages:
    1,124
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    51
    Location:
    Berks, England
    Ratings:
    +45
    Fantastic quality, but it can be a lot of work, see the recent avs.com thread for the gory details!

    regards,
    Rob.
     

Share This Page

Loading...