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  1. Member
    Join Date: Jul 2008
    Location: United States
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    Hello everyone,

    So I capture video at 60 fps (can't capture at 30 fps). I'd like to scale the video down to 30 fps (skip every other frame... do whatever). I'm able to do so in virtualdub, but the audio gets all messed up. I would be more specific... but there really aren't words to describe it :P.

    Anyways, I was wondering how I can say maybe convert to 30 fps by processing every other frame and keep the audio in sync.

    Thanks everyone.
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  2. BuskerAlley.com zoobie's Avatar
    Join Date: Feb 2005
    Location: Colorado Rocky Mountains
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    best to find out why you can't cap at 30
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  3. Member darkknight145's Avatar
    Join Date: Feb 2007
    Location: Australia
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    are you sure it's 60 frames per second and not 60 fields per second, if it's fields per second this is correct for NTSC, no conversion needed
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  4. The Old One SatStorm's Avatar
    Join Date: Aug 2000
    Location: Hellas (Greece), E.U.
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    AIPTEK cameras capture at 60fps, I have the same problem myself. So do some mobile phones.

    I do a fast frame convertion with virtualdub when that is needed. I also keep the original as raw data, until a good solution appears. There are some solutions already out there, but they are far from perfect in my opinion (always).
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  5. Make sure you change the frame rate in the correct section of VirtualDub's frame rate dialog:



    This will simply throw away every other frame and create a 30 fps video.

    You can do the same with AviSynth's ChangeFPS(30) or SelectEvery(2, 0).
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  6. Member
    Join Date: Jul 2008
    Location: United States
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    Originally Posted by jagabo
    Make sure you change the frame rate in the correct section of VirtualDub's frame rate dialog:



    This will simply throw away every other frame and create a 30 fps video.

    You can do the same with AviSynth's ChangeFPS(30) or SelectEvery(2, 0).
    In virtualdub, that still desyncs the audio for me.
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  7. Originally Posted by kelcey
    In virtualdub, that still desyncs the audio for me.
    Did you get the VBR audio warning when you opened the source video? What version of VirtualDub are you using? Starting around 1.7.something the VBR audio issue was fixed (it still gives a warning). Get the latest stable build (1.8.0 I think) if you don't have a recent version.

    If your audio is off by a fixed amount over the entire video you can use the audio skew function to shift it forward or backward (under Audio -> Interleaving).
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  8. Member edDV's Avatar
    Join Date: Mar 2004
    Location: Northern California, USA
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    Any live 480p or 720p broadcast will be 59.94 frames per second. 480i and 1080i will be 59.94 fields per second (29.97 frames per second). All update motion at the 59.94 rate.

    If you drop the 480p or 720p frame rate to 29.97, the video will appear just as choppy as if you viewed just one field of 480i or 1080i.
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  9. Member
    Join Date: Jul 2008
    Location: United States
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    Let me see if I can create some very short clips. I'll overly compress the video so it'll be a tiny download.
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  10. Member edDV's Avatar
    Join Date: Mar 2004
    Location: Northern California, USA
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    Originally Posted by kelcey
    Let me see if I can create some very short clips. I'll overly compress the video so it'll be a tiny download.
    Huh? You want tiny? For download?
    Tell us more.
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  11. Member
    Join Date: Jul 2008
    Location: United States
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    I meant I'm going to create 2 clips. One will be the original 60 fps. One will be converted 30 fps. I'm going to compress them a lot so they're easy to download.
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  12. Member
    Join Date: Jul 2008
    Location: United States
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    Okay. So I've gotten it to work using SelectEvery(2,0) in avisynth. Thanks jagabo.

    I actually tried changeFPS late last night... but maybe I mistyped it because some error popped up and I was tired. But selectevery works beautifully. Anyways, to let you know what happens when I use virtualdub convert to fps... the audio either just gets mangled (sounds like it slows down... maybe a mix of audio from various places?) or it just drops audio completely. I also didn't get the VBR warning. But anyways, I'm using MeGUI with avisynth now and it's working very well.

    Thanks for the suggestions everyone!
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