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  1. Member
    Join Date: Mar 2014
    Location: Brazil, Rio de Janeiro
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    I have an .avi file like this:



    I used Camstudio's Lossless Codec to record it.

    Why does the codec sometimes record at 59.998fps instead of 60fps? Is that normal?
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  2. Member Cornucopia's Avatar
    Join Date: Oct 2001
    Location: Deep in the Heart of Texas
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    Don't know. 59.998 is not any standard, 59.94 and 60 are.

    My guess would be matching your non-standard screen refresh rate?

    Scott
    "When will the rhetorical questions end?!" - George Carlin
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  3. I'm a Super Moderator johns0's Avatar
    Join Date: Jun 2002
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    If the file plays in sync all the way through i wouldn't worry about it,it's such a small amount.
    I think,therefore i am a hamster.
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  4. vanished El Heggunte's Avatar
    Join Date: Jun 2009
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    Originally Posted by synnchan View Post
    I have an .avi file like this:

    Sorry for the nitpick, but that's NOT "an .avi file", it's a VirtualDub setting

    As for CamStudio, well, probably it sucks by definition , so if I were you, I would look for better alternatives.
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  5. Member
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    Originally Posted by El Heggunte View Post
    Originally Posted by synnchan View Post
    I have an .avi file like this:

    Sorry for the nitpick, but that's NOT "an .avi file", it's a VirtualDub setting
    ..........Seriously, I know it's a virtualdub setting. What I wanted to mean is that this setting is pointing out information about my .avi file.

    Originally Posted by johns0 View Post
    If the file plays in sync all the way through i wouldn't worry about it,it's such a small amount.
    That's true, I can't even notice any difference in sync. I think nobody would unless if they are a robot. So maybe I don't need to worry.
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  6. I'm a Super Moderator johns0's Avatar
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    The reason there's that difference is cause lots of times the audio is a tiny bit shorter than the video but is still in sync,it just ends like .05 seconds sooner than the video.
    I think,therefore i am a hamster.
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  7. Originally Posted by johns0 View Post
    The reason there's that difference is cause lots of times the audio is a tiny bit shorter than the video but is still in sync,it just ends like .05 seconds sooner than the video.
    Or longer and ends later.
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  8. Yeah.... the assumption that it sometimes records at 59.998fps instead of 60fps appears to be wrong. It probably is 60fps, but the video and audio streams have slightly different durations. Nothing to worry about as long as they're in sync. Or...

    There's a way of using variable frame rate video in AVIs. I can't remember how it's done technically, and your video probably isn't variable frame rate, but.....
    Sometimes frames can be repeated instead of being encoded more than once, which effectively means their duration is longer than that of a normal frame (2x or 3x times etc). The same thing might happen if a frame is dropped while recording for some reason. In fact, if a frame is dropped, I'd assume that's what should happen. The preceding frame would need to have a duration of two normal frames. The frame rate is still constant, but it effectively varies, depending on how you look at it. If you opened such an AVI with VirtualDub, I'm pretty sure it'll report the original (constant) frame rate correctly (60fps in your case) but the "change frame rate to match audio duration" option will show a slightly different frame rate. Maybe something like 59.998fps, as an example. I gather it's because VirtualDub's frame rate option assumes every frame has the same duration, in which case the frame rate would need to be modified slightly for the video and audio lengths to match, but doing so would probably put the audio out of sync. In other words, the video and audio durations could actually match but VirtualDub is misleading you.

    Chances are the frame rate is constant and the video and audio durations are slightly different, but they're still in sync. If the video happens to be variable frame rate and you save it using direct stream copy, the "no change" frame rate option shouldn't mess with it. It'll stay variable. If it is variable I'm not sure how VirtualDub handles it when re-encoding.... whether it keeps the original frame durations or encodes "duplicate" frames more than once etc, but I'd assume it won't mess with the frame rate unless you tell it to.
    Last edited by hello_hello; 3rd Sep 2014 at 02:06.
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