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  1. I've wondered about this for a while now but never got round to finding out why this happens.

    Over time I've been backing-up my blu-rays and using handbrake for the encoding of the video. Now when I choose the FPS and the FPS mode, I choose constant framerate but when looking at the finished results with mediainfo, it shows that the FPS is variable and not constant. Why is this?


    Results from mediainfo
    Code:
    GeneralFormat                                   : MPEG-4
    Format profile                           : Base Media / Version 2
    Codec ID                                 : mp42
    File size                                : 51.4 MiB
    Duration                                 : 1mn 0s
    Overall bit rate mode                    : Variable
    Overall bit rate                         : 7 189 Kbps
    Encoded date                             : UTC 2036-02-06 06:28:16
    Tagged date                              : UTC 2036-02-06 06:28:16
    Writing application                      : HandBrake 0.10.2 2015060900
    
    
    Video
    ID                                       : 1
    Format                                   : AVC
    Format/Info                              : Advanced Video Codec
    Format profile                           : High@L4.1
    Format settings, CABAC                   : Yes
    Format settings, ReFrames                : 5 frames
    Codec ID                                 : avc1
    Codec ID/Info                            : Advanced Video Coding
    Duration                                 : 1mn 0s
    Bit rate                                 : 6 506 Kbps
    Width                                    : 1 920 pixels
    Height                                   : 800 pixels
    Display aspect ratio                     : 2.40:1
    Frame rate mode                          : Variable
    Frame rate                               : 23.976 fps
    Minimum frame rate                       : 23.974 fps
    Maximum frame rate                       : 23.981 fps
    Color space                              : YUV
    Chroma subsampling                       : 4:2:0
    Bit depth                                : 8 bits
    Scan type                                : Progressive
    Bits/(Pixel*Frame)                       : 0.177
    Stream size                              : 46.8 MiB (91%)
    Writing library                          : x264 core 142 r2479 dd79a61
    Encoding settings                        : cabac=1 / ref=5 / deblock=1:-2:-2 / analyse=0x3:0x113 / me=umh / subme=8 / psy=1 / psy_rd=1.00:0.25 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=6,6 / fast_pskip=1 / chroma_qp_offset=-4 / threads=12 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=0 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=2 / b_bias=0 / direct=3 / weightb=1 / open_gop=0 / weightp=2 / keyint=240 / keyint_min=24 / scenecut=40 / intra_refresh=0 / rc_lookahead=50 / rc=2pass / mbtree=1 / bitrate=6506 / ratetol=1.0 / qcomp=0.80 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=62500 / vbv_bufsize=78125 / nal_hrd=none / filler=0 / ip_ratio=1.10 / aq=1:0.50
    Encoded date                             : UTC 2036-02-06 06:28:16
    Tagged date                              : UTC 2036-02-06 06:28:16
    Color range                              : Limited
    Color primaries                          : BT.709
    Transfer characteristics                 : BT.709
    Matrix coefficients                      : BT.709
    If this is in the wrong section then admins/mods, feel free to move this to the correct section.
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  2. Member
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    If you manually select frame rate instead of using 'Same As Source' you won't have that problem. Yes it is an annoyance in Handbrake.
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  3. Originally Posted by Dougster View Post
    If you manually select frame rate instead of using 'Same As Source' you won't have that problem. Yes it is an annoyance in Handbrake.
    Forgot to mention that I do select the framerate manually. The settings I use for framerate are in the image below.

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  4. I'm a MEGA Super Moderator Baldrick's Avatar
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    You could try latest handbrake beta( https://handbrake.fr/nightly.php ) or vidcoder beta see how they work.
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  5. It's because of the timescale HandBrake uses. 23.976 is 24000/1001 fps rounded so for exact constant frame rate storing a muxer would have to use 24000 as a base for timings and then just stamps by 1001 for each frame. But HandBrake always uses 90000 for the timebase which means you cannot exactly represent 24000/1001 fps. You end up having to alternate between 3753 and for 3754 for the timestamp so you end up with a minimum and maximum of 90000/3753 ~= 23,981 and 90000/3754 ~= 23,974 fps, the average being ~23.976 fps.
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  6. For whatever reason, MediaInfo seems more likely to "correctly" interpret the frame rate type if the output is MKV rather than MP4, although I'm sure on occasion I've seen it label MKVs as variable frame rate which are supposed to be constant frame rate.

    If it really bothers you, try opening the output video with a muxing program and remux while specifying the correct constant frame rate. It shouldn't have any noticeable effect aside from changing the way MediaInfo sees the video. It works when remuxing with MKVMergeGUI but for MP4's I'm not sure. You could try MyMP4BoxGUI to see if it does.
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  7. Originally Posted by hello_hello View Post
    For whatever reason, MediaInfo seems more likely to "correctly" interpret the frame rate type if the output is MKV rather than MP4, although I'm sure on occasion I've seen it label MKVs as variable frame rate which are supposed to be constant frame rate.
    It's not possible to do exact 24000/1001 fps in mkv, you will always have a jitter similar to the one in HandBrake's MP4 files. MediaInfo treating them differently is kind of a double standard, if you will.
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  8. Handbrake, VDub, & MeGUI tjack360's Avatar
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    Originally Posted by sneaker View Post
    It's because of the timescale HandBrake uses. 23.976 is 24000/1001 fps rounded so for exact constant frame rate storing a muxer would have to use 24000 as a base for timings and then just stamps by 1001 for each frame. But HandBrake always uses 90000 for the timebase which means you cannot exactly represent 24000/1001 fps. You end up having to alternate between 3753 and for 3754 for the timestamp so you end up with a minimum and maximum of 90000/3753 ~= 23,981 and 90000/3754 ~= 23,974 fps, the average being ~23.976 fps.
    Fantastic explanation! I always have wondered why that happens with Handbrake but never looked for an answer before now. Thanks!
    Toshiba DX1215, Intel Core i5-2410 CPU 2.30GHz 2.30 GHz, 8.00 GB RAM, Windows 10 Home 64-Bit OS
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