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  1. Member
    Join Date: Nov 2013
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    Can x265 HEVC have variable frame rate? Can I do this in FFmpeg? Thanks.
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  2. Member
    Join Date: Sep 2007
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    Docs don't say anything about a tcfile-in or timecodes file. But you can use mkvmerge with timecodes to make it VFR
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    Okay, maybe I'll try that. Thanks!
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  4. Member Cornucopia's Avatar
    Join Date: Oct 2001
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    Foolish thing to do, though. Down the road, you'll regret it.

    Scott
    "When will the rhetorical questions end?!" - George Carlin
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  5. Member
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    You mean because it's nonstandard?
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  6. Member Cornucopia's Avatar
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    I mean, because it invariably causes trouble with a multitude of hardware & software devices, and, ultimately, is unnecessary given good vbr algorithms. HEVC, and even AVC, is efficient as it is. And because it doesn't "play well with others".

    The assumed "benefits" never outweigh the deficits, and those benefits can be easily gotten with other, more reliable techniques. Motion-compensated long GOP VBR can already get you 90% of the way to any intended efficiency.

    Scott
    "When will the rhetorical questions end?!" - George Carlin
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  7. Originally Posted by Cornucopia View Post
    I mean, because it invariably causes trouble with a multitude of hardware & software device
    Which ones?
    Not that I use VFR myself, but I have a little VFR video and no problems playing it to date. Handbrake defaults to VFR mode and you'd assume if VFR was generally problematic that wouldn't be the case.

    MKV doesn't even use frame rates as such. It uses durations/timecodes instead. Are there MKV capable players which don't support MKV timecodes correctly? https://trac.bunkus.org/wiki/FAQ%3AWrongFrameRateDisplayed
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  8. Member
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    Hardware players like "media harddisks" or TV sets with integrated media players (e.g. reading from USB devices) will probably refuse to play VFR content, even though they may support the media format; but they won't know how to adapt to a changing framerate.
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  9. Member Cornucopia's Avatar
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    And I have VFR video also (from my android phone), and HAVE had problems, even in the single year I've used it, both in playing and (especially) in editing. You've just been very lucky so far. This site is LITTERED with threads trying to resolve problems with VFR.

    Handbrake is a great app, but if it DEFAULTS to suggesting to use VFR, that is foolish. I don't care who designed it - it should be changed.

    We've already gone over the whole "MKV does/doesn't have framerates" before. Yes, it does, it just does it in a way (durations/timecodes) that is consistent for both VFR and CFR, using CFR as a strict subset of general VFR capability. And an app would need to be able to read those headers correctly to be able to play MKV correctly. But that same app may not be able to actually, correctly play VFR just because it can read the headers.

    Actually, I'm kind of surprised at your response. For someone who has been vocal about their sensitivity to time instability with NTSC pulldown, I would expect the even more egregious variations of framerate (and accompanying motion inconsistency) would be nerve-wracking. I mean, there are demonstrated online examples of phone recordings that were preset for 30fps which varied in actual framerate from 7.5 to ~32fps. Think about what wheel spoke movement would look like with that much ridiculous variation!

    Scott
    "When will the rhetorical questions end?!" - George Carlin
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  10. I asked because I've read lots of threads where people have had problems, and any sign of VFR immediately gets the blame, but sometimes the problem has turned out to be something else, much like this thread:
    http://forum.videohelp.com/threads/366610-Crop-videos-without-re-encoding?p=2341340&vi...=1#post2341340
    I'm not sure the forum is littered with threads along the lines of "I have a problem", "it's caused by variable frame", "that's correct, changing to constant frame rate fixed it"..... but maybe I've missed those threads.

    As I said, I don't have much VFR video but I found a VFR MKV. If I open it via an Avisynth script the audio wanders out of sync unless I add CFR conversion to the script, which keeps it in sync. When I do add CFR conversion the frame count changes by a couple of hundred (the video is about 10 minutes long). The media player in my TV doesn't have any trouble playing it.
    I re-encoded it with Handbrake as an MP4 and tested the encoded version with the TV's media player. It played the MP4 fine too. This is what MediaInfo says about it:

    Frame rate mode : Variable
    Frame rate : 29.786 fps
    Minimum frame rate : 14.925 fps
    Maximum frame rate : 47.619 fps

    Maybe I am just lucky. I'm not advocating using VFR, I just haven't found it as problematic when it comes to playback as it's often claimed it would be. Much like the sky doesn't fall if the audio is variable bitrate. Which players have given you trouble when trying to play VFR video?
    Last edited by hello_hello; 9th Sep 2014 at 08:20.
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  11. Member
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    AviSynth simply does not support VFR; you would have to extract the timing and re-apply it to the copy (no comments about how-to here). So pretty much all AviSynth based conversion tools may not be suitable here.

    Hardware players having issues with VFR is not absolutely certain, but quite probable. It may depend on the container. Variable framerate is often just caused by skipping single frames, but still being in some kind of higher-frequency clock rate, to which the player may be able to adapt, and skip an integer number of clock cycles, possibly a different number for each frame, but not a completely arbitrary duration per frame.
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  12. Originally Posted by LigH.de View Post
    AviSynth simply does not support VFR; you would have to extract the timing and re-apply it to the copy (no comments about how-to here)
    I've done that on occasion when working with a VFR source. The result can be better than trying to convert to a constant frame rate by repeating/dropping frames and/or with frame blending. I guess it depends on the source.
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  13. Member Cornucopia's Avatar
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    I couldn't tell you right now just what apps had difficulty, as the last time I dealt with VFR was probably this last April, and with me using ~5-6 different video apps every day, it gets too much to keep track of. I do know that just about ALL of the standard pro video NLEs will NOT work with VFR correctly. From what I can tell, a comprehensive FR-polyglot/fluent NLE does not yet exist.

    However, you've piqued my interest with this subject, so I'm going to make a point of logging each app I use and see how it reacts to VFR (should I have VFR video to work with at the time). Down the road, I'll let you all know which ones. Plus, I plan on digging alot deeper on the variations in the technology and their assumptions, so that I can be on firmer footing the next time I need to accommodate it.

    I'll shut up now so the thread can get back on topic...

    Scott

    <edit>Hmm...I see parallels with Variable Sample Rate audio!...Aliasing?</edit>
    Last edited by Cornucopia; 9th Sep 2014 at 13:05.
    "When will the rhetorical questions end?!" - George Carlin
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  14. I can see how editing VFR video could be a problem, but I'm curious as to how much of a problem it causes when it comes to normal playback scenarios. If you have any interesting discoveries.....
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