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slow motion with virtualdub?

Discussion in 'Other video questions' started by clmetal, Feb 29, 2008.

  1. clmetal

    clmetal Member

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    I know how to lower the frame rate to slow a video down, but you can't attend video segments with different frame rates.

    Does anyone know how I can use virtual dub to slow down part of my video but not all of it?

    thanks
     
  2. attar

    attar Senior member

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    Assuming that you have one file and you want a part of it (the middle) in slow motion then you can do it this way.
    Note, that I also compress the audio - VirtualDub seems to be fussy that way.
    Load the file, note the video FPS and audio sample rate in the file information.
    Assume 25fps and 44100, 128 stereo.

    Select the first part (which will be normal speed) and click 'Audio' 'Full Compression' and choose the original compression (44100,128 etc).
    'Video' 'Direct Stream Copy' and save the first part (p1).

    Clear the edit, but don't move the slider.
    Set the new start point for the second (slow motion part) and the end point.
    'Video' 'Direct stream Copy' 'Frame rate' 'Change Frame Rate to FPS' and enter 12.5 , then beneath that in the next section, choose 'Convert to FPS' and insert 25.

    At this point you could click 'Audio', select the compression again and save the new clip, but you might want to make the sound 'normal but slowed down' by selecting 'Use Advanced Filtering' 'Filters'.
    Add the filters 'Input' 'Stretch' 'Ratty Pitch' and 'Output'
    Click on 'Stretch' and enter '2', click on 'Ratty' and enter '2' - don't forget to compress the audio, save the new AVI and importantly, reset the video frame rate and turn off the advanced filter.

    Clear the edit point again and select the third part, recompress the audio, and video direct stream copy and save it.

    Close and reopen VirtualDub.
    Load part 1 then append the rest.
    Note:if you have saved the parts with names like p1, p2, p3, the VirtualDub will append p2 and p3 at the same time.
    Save the new file with direct stream video and audio.

     
  3. clmetal

    clmetal Member

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    thanks a million, I will try it this week. (was afraid VDM wouldn't work for this)

    I plan on using music in the background to replace what the video had, so I will add that in as the last step after the video is made
     
  4. clmetal

    clmetal Member

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    what you said works, thank you. But I constantly get errors trying to append saying the frame rates are different. (rediculous differences like saying one is 29.000 and the other is 29.003)
     
  5. attar

    attar Senior member

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    The append feature is allegedly used to join clips that had previously been split with VirtualDub - thus they would be identical as to everything (except length).
    Both files may need the video recompressed with the same codec then appended.
    Also note that the appended file may have a sync problem, to fix that you have to clip a couple of frames from the first file (key frame?), save it, then append the second file.
     
  6. clmetal

    clmetal Member

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    thanks - instead of leaving the frame rate unchanged, I have it changed to a very similar frame rate and then I do a convert to fps.

    seems to get rid of the rounding errors that result in vdm saying the frame rate is different

    I am making videos with slow motion thanks to you, so thanks
     
  7. attar

    attar Senior member

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