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  1. I am trying to convert 29.97fps capture to 25fps capture so that i can copy to dvd.

    I thought by following the guides on here that go from 23.976 to 25fps would bring about the same results which have for me been very successful.

    I am using VirtualDub and Besweet and Avirate.

    I can extract the audio then save as wave using vdub. I then convert the wave from 29.97fps to 25fps using Besweet and its templates. This is where the problem seems to be. The lenght of the original video is 58 mins but the newly converted 25fps audio file is 1 hr 10 mins. Quite a bit bigger and it sounds slow.

    i continued however to see what happened. I changed the header on original video to 25fps using AVIrate and then loaded file into vdub.I disable orignal audio wave and put the new 25fps audio file i created earlier in its place and create new 25fps audio and video that is completely in sync but the sounds is slow. (ie audio sounds like its been slowed down)

    Is it possible to do this conversion. I have seen someone else have a similar kind of problem but it was there video that was the issue and not the audio.

    Can anyone see anything that i am doing wrong or missing out.

    I then change header on file from 29.97 to 25 using avirate.

    Like i said i can convert from 23.976 fps to 25fps using the above method no problems at all.
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  2. Member
    Join Date
    Apr 2002
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    The State of Frustration
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    I wish I could see what you are doing for two reasons:

    1. We measure audio speed in Hertz (Hz). So your DVD audio should be 48000 Hz.

    2. We measure video speed in frames per second (fps). So DVD NTSC video is 23.97 or 29.97 fps. So needless to say, I am confused.
    Hello.
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  3. In answer to your questions. The original source video i have is NTSC 29.97 fps with audio 48000hz

    I am trying to convert this to PAL 25fps 48000 as i live in UK and my dvd player does not play NTSC 29.97 or 23.97.

    The audio is already 48000hz but the problems arises when changing the frame rate from 29.97fps down to 25 fps. You also have to adjust the audio to keep it in sync. AS i have said i managed to convert the video no problem to 25fps but when the audio is changed from 29.97 fps to 25fps its in sync with the video but it sounds slow.

    Please note i am using the terminolgy of frames per second for the aduio part so it make sense with the video frame rate and not because i think audio is measured in frames per second.
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  4. The problem is that the guides for NTSC film (23.976fps) to PAL progressive/film (25fps) rely on an important factor -- the difference in framerate is insignificant (only 4%).

    The difference between 29.97fps and 25fps is 16.5%!! The action on-screen will be VERY noticably slowed, as well.

    If the video is actually telecined film source (step through the file to check, you will see a pattern 3:2 pattern of interlaced/non-interlaced frames), you can do an inverse telecine and get 23.976fps source, which you can then convert. You will get better quality this way.

    Anyway, the conversion is usually done by dropping frames and cleverly blending to make it not so jerky. This does not change the total running time of the video, so no audio change is requried.

    There are two easy methods I can think of off the top of my head to do the conversion:

    1. If you are using TMPGEnc, simply let it convert. TMPGEnc does not do any clever blending, however, so it will be jerky.

    2. Use Avisynth. If you are not aware, it is a scripting language that uses a fake AVI file to "frameserve" processed video through to another application. This allows you to do blending to get better results.

    If the source is not interlaced it is nice and easy.

    An Avisynth script to do a nice convert looks like this:

    Code:
    AviSource("filename.avi")
    ConvertFPS(25)
    If it is interlaced it is slightly more complicated. (Partially copped from the Avisynth website)

    Code:
    AviSource("filename.avi")
    
    Bob() # Separate fields and interpolate them to full height.
    
    BicubicResize(720, 576)
    
    ConvertFPS(50) # Convert field rate to PAL, using Blend Mode.
    
    # Undo Bob, even field first. Use SelectEvery(4, 1, 2) for odd field first.
    SeparateFields.SelectEvery(4, 0, 3) 
    
    Weave # Finish undoing Bob.
    That would work for mixed (part video, part film) clips but if it is entirely film, do an IVTC and you'll be much happier with the 4% speedup results. It'll look exactly like any commercial movie release.
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  5. Thank you. This is what i think i wanted to know.

    I will give this a bash over the next day or two and let you know how i got on.

    Cheers
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