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  1. I found your site through this link: https://forum.videohelp.com/threads/384727-Can-anyone-say-which-tool-method-use-to-con...e-2-vid-files-!!! and have a similar question.

    I have been given two versions of a video and am trying to figure out how the smaller file was created. Like the link poster, I was able to collect their MediaInfo details, which are:


    1) Smaller File:

    General
    Complete name : small_XXX.mp4
    Format : MPEG-4
    Format profile : Base Media
    Codec ID : isom (isom/iso2/avc1/mp41)
    File size : 375 MiB
    Duration : 1 h 2 min
    Overall bit rate : 841 kb/s
    Writing application : Lavf57.71.100

    Video
    ID : 2
    Format : AVC
    Format/Info : Advanced Video Codec
    Format profile : Main@L3.1
    Format settings : CABAC / 4 Ref Frames
    Format settings, CABAC : Yes
    Format settings, ReFrames : 4 frames
    Codec ID : avc1
    Codec ID/Info : Advanced Video Coding
    Duration : 1 h 2 min
    Bit rate : 705 kb/s
    Width : 872 pixels
    Height : 486 pixels
    Display aspect ratio : 16:9
    Frame rate mode : Constant
    Frame rate : 30.000 FPS
    Color space : YUV
    Chroma subsampling : 4:2:0
    Bit depth : 8 bits
    Scan type : Progressive
    Bits/(Pixel*Frame) : 0.055
    Stream size : 314 MiB (84%)
    Writing library : x264 core 148
    Encoding settings : cabac=1 / ref=4 / deblock=1:0:0 / analyse=0x1:0x111 / me=hex / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=0 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=15 / lookahead_threads=2 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / bluray_compat=0 / constrained_intra=0 / bframes=3 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=120 / keyint_min=12 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=crf / mbtree=1 / crf=22.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / ip_ratio=1.40 / aq=1:1.00
    Language : English
    Color range : Limited
    Color primaries : BT.601 NTSC
    Transfer characteristics : BT.709
    Matrix coefficients : BT.601
    Codec configuration box : avcC

    Audio
    ID : 1
    Format : AAC LC
    Format/Info : Advanced Audio Codec Low Complexity
    Codec ID : mp4a-40-2
    Duration : 1 h 2 min
    Bit rate mode : Constant
    Bit rate : 128 kb/s
    Channel(s) : 2 channels
    Channel layout : L R
    Sampling rate : 48.0 kHz
    Frame rate : 46.875 FPS (1024 SPF)
    Compression mode : Lossy
    Stream size : 57.1 MiB (15%)
    Language : English
    Default : Yes
    Alternate group : 1



    2) Larger File:

    General
    Complete name : large_XXX.mp4
    Format : MPEG-4
    Codec ID : M4V (isom/avc1/mp42)
    File size : 1.35 GiB
    Duration : 1 h 2 min
    Overall bit rate mode : Variable
    Overall bit rate : 3 105 kb/s
    Encoded date : UTC 2019-11-29 04:23:18
    Tagged date : UTC 2019-11-29 04:23:18

    Video
    ID : 1
    Format : AVC
    Format/Info : Advanced Video Codec
    Format profile : Main@L3.1
    Format settings : CABAC / 3 Ref Frames
    Format settings, CABAC : Yes
    Format settings, ReFrames : 3 frames
    Codec ID : avc1
    Codec ID/Info : Advanced Video Coding
    Duration : 1 h 2 min
    Bit rate mode : Constant
    Bit rate : 3 000 kb/s
    Maximum bit rate : 7 336 kb/s
    Width : 1 280 pixels
    Height : 720 pixels
    Display aspect ratio : 16:9
    Frame rate mode : Constant
    Frame rate : 30.000 FPS
    Color space : YUV
    Chroma subsampling : 4:2:0
    Bit depth : 8 bits
    Scan type : Progressive
    Bits/(Pixel*Frame) : 0.109
    Stream size : 1.31 GiB (97%)
    Encoded date : UTC 2019-11-29 04:23:18
    Tagged date : UTC 2019-11-29 04:23:18
    Color range : Limited
    Color primaries : BT.601 NTSC
    Transfer characteristics : BT.709
    Matrix coefficients : BT.601
    Codec configuration box : avcC

    Audio
    ID : 2
    Format : AAC LC
    Format/Info : Advanced Audio Codec Low Complexity
    Codec ID : mp4a-40-2
    Duration : 1 h 2 min
    Bit rate mode : Variable
    Bit rate : 96.0 kb/s
    Maximum bit rate : 99.9 kb/s
    Channel(s) : 2 channels
    Channel layout : L R
    Sampling rate : 48.0 kHz
    Frame rate : 46.875 FPS (1024 SPF)
    Compression mode : Lossy
    Stream size : 42.8 MiB (3%)
    Language : English
    Encoded date : UTC 2019-11-29 04:23:18
    Tagged date : UTC 2019-11-29 04:23:18



    The content is identical. I made the file names more specific for the sake of clarity. The smaller file was made (or is dated) about a year and a half before the larger file. My computer is old and slow so I tend to view these on the TV from a USB stick. I don't understand why the large file has to be over 3 times the size of the small file when they look and sound pretty comparable to me. Based on the MediaInfo, it even looks like the audio on the smaller file is higher quality. I am afraid I am being left behind with my older system as these file sizes grow exponentially and want to keep it as functional as long as I can.

    Ultimately, I guess I am asking how one would go about turning the larger file into the smaller file on a Mac?
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  2. The smaller file was encoded with x264. The settings are listed. They correspond to the medium preset at CRF 22. except for keyint=120 and keyint_min=12. Any tool that uses the x264 will work. Most free tools use x264, Handbrake, for example.

    But the smaller file also uses a much smaller frame size, 872x486 vs. 1280x720 (Handbrake can downscale like this). The smaller frames require fewer bits, hence a smaller file. But that's treading off resolution to get a smaller file.
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  3. Member Cornucopia's Avatar
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    Know that if you attempt to take the larger one and reduce it, you will be lossily re-encoding with some accompaying loss of quality. Probably not worth the effort, if you are already ok with the smaller one.

    Scott
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  4. Hi guys,

    Thanks for the insight. I will look at the two versions of this file more closely before deciding whether to proceed. I'm more interested in being able to archive other examples more efficiently that I only have at the higher resolution/larger file size since they eat up so much real estate at their full size. Much appreciated.

    Forgot, one other question: Is it only the smaller frame size that accounts for the difference in file size?
    Last edited by harrisonfree; 21st May 2020 at 09:02. Reason: added question
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  5. Originally Posted by harrisonfree View Post
    Forgot, one other question: Is it only the smaller frame size that accounts for the difference in file size?
    The smaller frame size requires less bit rate in order to achieve a similar bit/pixel ratio.

    The 1280x720 has a ratio of Bits/(Pixel*Frame) : 0.109

    The 872x486 has a ratio of Bits/(Pixel*Frame) : 0.055

    Not taking into account the difference in frame size, the larger file has roughly twice the quality per pixel than the smaller file, on a larger monitor or TV chances are you would notice the quality difference.
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  6. Originally Posted by harrisonfree View Post
    Forgot, one other question: Is it only the smaller frame size that accounts for the difference in file size?
    No, the lower bitrate accounts for the smaller file size. The smaller frame size allows for fewer compression artifacts at that lower bitrate. But again, you're trading off resolution to get fewer compression artifacts. If you view both of the videos full screen you'll see that the smaller video is not as sharp. Taking this to the extreme, you could reduce the resolution to 1x1 pixel and save with no compression at all and get a tiny file. But viewing that video wouldn't be very interesting.

    There may also be differences in the codecs. Not all h.264 encoders are created equal. And not all settings deliver the same quality at the same bitrate.
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