Dropped frames once transcoded how to stop it?

Discussion in 'Apple TV and Home Theater' started by MacBoobsPro, Apr 10, 2008.

  1. MacBoobsPro macrumors 603

    MacBoobsPro

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    Jan 10, 2006
    #1
    For a while now I have had various success when transcoding movie files to watch on my ATV.

    Some convert fine others seem to drop frames and stutter at once every second. Seemingly indicating dropped frames? I don't know exactly because I'm not a 'video guy'.

    Something I discovered today is that I have an AVI file that is 25fps and for ATV to be able to play it it needs to be 24fps so I bung it in VisualHub on the ATV setting with 'Go Nuts' selected. Once the file has finished when I check its fps in QT it says 24 but it plays at 23.98 and jerks every second or so. This happens on a few of my files.

    Why does it only play at 23.98 and not 24? I guess the 'jerk' is for it to make up for the missing .2?

    Does dropping from 25 to 24 cause any ill effect on videos in general?

    And how can I possibly fix the problem so my files play without going all jerky and annoying.

    Cheers
     
  2. mac2mac macrumors member

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    UK
    #2
    Thats not why its jerking

    Yes always keep the FPS the same as the original if possible so in your case in Advanced in VisualHub type "25" in FPS:
    [​IMG]
     

    Attached Files:

  3. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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    #3
    But what if its a HD file (1280 x 720) and the original is 25fps but ATV needs 24 at that resolution?

    Also why is it jerking?

    Forgive me if there are obvious answers to these questions but I'm still getting my head round video and its various nuances.
     
  4. killmoms macrumors 68040

    killmoms

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    #4
    Only if it's 720p.

    23.976 = NTSC FILM playback rate. No, there is no missing .2.

    Yes, because it drops frames, instead of simply slowing down as it should.

    Don't change frame rate.
     
  5. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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    #5
    Ok thanks for that killmoms but what do I do if it is 720p. Which some are.
     
  6. killmoms macrumors 68040

    killmoms

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    #6
    Then I'd assume it's film content which was sped up for broadcast over PAL television? You'd need to slow it back down to 24, and I'm not sure what utilities would do that without re-encoding on OS X. I'm not even sure if there are any.

    The reason it's jerking is because VisualHub is actually dropping frames from the video to keep the same real-time length. What you actually want to do is slow the whole thing back down to 24fps.
     
  7. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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    #7
    Wow you're good. When I read that I noticed all the files are indeed from PAL TV. :p

    So you don't know of a way of slowing them down?
     
  8. killmoms macrumors 68040

    killmoms

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    #8
    Well, it looks like JES Deinterlacer can do it, but you'd need to create an intermediate file in a format like Apple Intermediate (which would be quite large) and then transcode with VisualHub. Unless you want to go straight out of JES using Quicktime's H.264 encoder.
     
  9. mac2mac macrumors member

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    #9
    Have you tried playing a 1280x720 video at 25 fps on the appletv? sometimes more video can be played than the specification says.
     
  10. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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    #10
    I think I'll give that app a miss the site doesn't fill me with confidence.

    I guess I could give it a go although the maximum stated by Apple is 1280x720 at 24fps.
     
  11. killmoms macrumors 68040

    killmoms

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    #11
    Wait. What? ...Um, okay. That app is one of the best deinterlacers available on OS X, we use it here at the high-end post-house I work at in L.A. but, uh, whatever makes you feel good I guess.

    Just because a website's not flashy doesn't mean the app's crappy. What a ridiculous thing to say. :rolleyes:
     
  12. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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    #12
    I didn't say that you did :D

    The app front end looks a bit 'smashed together' and so does the site so it leads me to believe the backend on both may also be somewhat 'iffy'. I'm trying to limit potential problems on my system and I am wary of downloading buggy apps that will stuff up my files and or system thats all.

    I know what you're saying don't judge a book by its cover but when that book has a stick of dynamite sticking out of a flaming dog turd on page 94 theres not much you can do once you have turned the page. :D

    Does the app work ok for you?
     
  13. killmoms macrumors 68040

    killmoms

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    #13
    Like I said, I work at a major post-production house in L.A. and we use it as part of our workflow for in-machine standards conversion. It's an excellent app. Just won't be winning any design awards anytime soon—which is often the case with technically great apps. Just see VirtualDub on the PC, which is amazingly versatile and capable but which has an interface that's crap. Or AVISynth which has NO interface.
     
  14. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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    #14
    I'll give it a whirl then but if it goes tits up I'll be coming for you :D

    LA is only a small place right?
     
  15. killmoms macrumors 68040

    killmoms

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    #15
    ...Los Angeles, California? The entertainment capital of the world?

    Now I think you're just taking the piss.
     
  16. MacBoobsPro thread starter macrumors 603

    MacBoobsPro

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  17. eddyg macrumors 6502

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    Christchurch, New Zealand
    #17
    leave it at 25fps

    Hi,

    The ATV should let you play 720p content at 25fps. It is not easy to convert 25fps to 24fps. When it was sped up in the first place they would have also have had to speed up the audio, ensuring no pitch shift.

    So to slow down, not only must you slow down the video but also change the rate of the audio, and do some pitch shifting.

    The ATV should really be fine with 720p@25fps, not that I've tried it yet.

    Cheers, Ed.
     
  18. bomadian macrumors member

    Joined:
    Mar 4, 2007
    #18
    Hi Macboobspro,

    I was wondering if you got anywhere with this problem. I have encoded movies using VH for ATV using go nuts and many are dropping frames evert few seconds, but the frame rate is 24 on the AVI file and the encoded ATV file is also 24. VH also managed to make the original 700MB file a 3GB file too! Any ideas? Can it be attributed to the fact I'm streaming from Time Capsule to ATV?
     
  19. kinkladze macrumors newbie

    Joined:
    Feb 28, 2009
    #19
    hey all

    I was wondering if we'd got anywhere with this issue?

    I'm trying to sort the exact same thing and 25fps 720 video plays all blurred on ATV, where as 24fps converted video plays fine but drops frames, obviously! both are no good

    any thoughts on a way around this. would encoding a smaller res video @ 25fps be a solution or am i missing something?
     

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