acceptable dropped frames during analog capture?

Discussion in 'Computers' started by Christ Reynolds, Mar 31, 2004.

  1. Christ Reynolds

    Christ Reynolds Producer

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    i have started the process of capturing the entire series of twin peaks from the vhs tapes i have. i started to capture the pilot episode, and i ended up with dropped frames. i figured i would capture uncompressed, and then use tmpegenc to encode the avi to the bitrate i needed. maybe it wasnt the best reasoning, but i wanted to have the video as close to native as possible. anyway, during the capture (352 x 480) i dropped 60 frames. should i worry about this? i have deleted the file already, but i wanted to know if i should keep it next time if it only drops around the same amount of frames. thanks.

    CJ
     
  2. Scott L

    Scott L Producer

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    Try capturing with the Huffyuv codec. It's lossless, very fast, but saves space color-wise so it doesn't take up as much space as raw RGB. Ideally zero dropped frames ensures your system is running smoothly, but if they are rare and spaced out, a couple of dropped frames are hard to spot out during playback.

    http://www.divx-digest.com/software/huffyuv.html

    And can I ask why the weird resolution ratio? Is it to squeeze out the interlacing somehow?
     
  3. Jeff Jacobson

    Jeff Jacobson Cinematographer

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    If your video tapes are in bad condition, this will also cause frame drops. (The slightest glitch on a video tape will cause dropped frames on my ATI AIW 7500.)

    If possible you should capture at 720x480, 29.97 frames/second. (I assume these are American tapes. If they are from europe, than you will have to use a different resolution and frame rate.)
     
  4. Christ Reynolds

    Christ Reynolds Producer

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    dont ALL videotapes have glitches on them? [​IMG] my tapes arent in the best condition, not bad either. i suppose they look as vhs should look - not terribly awful, with a fair amount of video noise. i'm going to try to clean these up with tmpegenc, it worked wonders on my terrible looking episodes of the upright citizens brigade. considering i put 11+ hours on one dvd, i'd say they look damn good.

    CJ
     
  5. Kelvin Tucker

    Kelvin Tucker Stunt Coordinator

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  6. Christ Reynolds

    Christ Reynolds Producer

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    thanks everyone. i'm sure i will have more questions along the way [​IMG]

    CJ
     
  7. Ken Chan

    Ken Chan Producer

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    You mean back to 704 or 720? That's a bad idea. Capturing at 720/704 and squeezing down to 352 is OK, but there's no point in blowing it up. It just wastes space. Any non-brain-dead DVD authoring program should accept 352x480 video -- it's part of the spec. Unfortunately, many are brain-dead.

    (If you're going from 720 to 352, the correct way is to first crop it to 704 by taking off 8 from each side -- or 4 and 12, 16 and 0, some multiple of 4, depending on the codec -- and then squeezing that in half exactly.)
     
  8. Christ Reynolds

    Christ Reynolds Producer

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    how? i have a reasonably fast cpu (athlon 1700+ @ 1.47GHz). i utilize around 20% of the cpu when capturing, either in huffyuv or uncompressed. how can i compress even more? i have tons and tons of hd space, but my hdd is probably only average speed, so it may not be able to keep up. i'd like to ease the strain on it if possible.

    CJ
     
  9. Christ Reynolds

    Christ Reynolds Producer

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    well i used huffyuv to capture, and i end up with a file that is 98 gb. not a problem, except that i cant read it with anything. i guess it may have to do with the file size, i'm not sure. i didnt have any problems with smaller files. i dropped 192 frames, 188 of which were dropped in the last 3 minutes of the tape, i'll have to look at the tape to see what is there. maybe it is the snow that comes on after the credits, i shut off the screen that shows what is being captured. any clues on why i cant open this file with anything?

    CJ
     
  10. Scott L

    Scott L Producer

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    sounds like it was the file looking for more space to put itself on your HD after getting so big. Maybe you should consider defragging first and breaking the file up into segments next time you capture.

    Try opening with Virtual Dub, if there's an error it usually will describe what it is.
     
  11. Ken Chan

    Ken Chan Producer

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    You may have missed a word; I'll try a slightly bigger one [​IMG] : one frame per minute, as opposed to one every ten minutes. And yes, that totals two seconds.

    Nope [​IMG] VHS may be crap, but it's not that bad. You're throwing away half of the info, and probably not in the best way. At 352x480 (MPEG-2), without doing anything else, you should be able to get 3 hours on a single-layer DVD. Since Twin Peaks was almost certainly shot on film, you could do inverse telecine and get close to 4 hours. It should look a lot better.
     
  12. Patrick Sun

    Patrick Sun Moderator
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    Try installing the Panasonic DV codec. This was the only that helped me in using VirtualDub with a captured DV file.
     
  13. Christ Reynolds

    Christ Reynolds Producer

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    ok here is my question in response to that. 352x480 is shaped awfully strange. how do i tell tmpegenc to use it? i have the kdvd template that is "half D1 352x480". when i use this template and output the video, will i still get this strange aspect ratio on my screen? i still have the original avi i captured, so i could change things without capturing again. i made a 352x240 mpg (seperate m2v and mp2) file, but i can always delete that. if i select my output as a 4:3 screen, will tmpeg and the dvd authoring program know to fill up my screen with just the picture i want? i guess the strange aspect ratio is what i dont understand.

    CJ
     
  14. Ken Chan

    Ken Chan Producer

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    Well, 352x240 isn't 4:3 either -- everything is a little fat. In fact, none of the VCD, SVCD, or DVD resolutions are 4:3. It's the players' job to stretch the pixels so that the picture comes out right. If you play 352x480 on a naive MPEG player, everything will be tall. But if you use a DVD player program, or a media player that checks are respects the aspect ratio setting of the MPEG video, or a DVD player connected to your TV, it will look correct.
     
  15. Jeff Jacobson

    Jeff Jacobson Cinematographer

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    If you open your Avi file in VirtualDub, you will be able to tell where the frame-drops are. The } key will take you to the next dropped frame, and the { key will take you to the previous one.
     

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