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  1. Member
    Join Date: Apr 2014
    Location: US
    Search Comp PM
    I am in the process of converting my Blu-rays and DVDs to MKV files on my home PC. After playing around with VidCoder, I got the settings to where I get the quality I want, and a file size that works for me. However, as I convert my Blu-ray movies, I am noticing a large discrepancy in the size of some of the mkv files, even though I am using the same conversion settings on each. I have only converted 10 movies so far, but the sizes range from 3.8GB to 15.4GB (note: so far only 1 file is 3.8GB - the rest are in the 8 to 15GB range). These movies are all 1080p and the length of each is about the same. Is this normal. or should I be adjusting some of the settings for certain movies? I just want to be sure I am not missing something before I convert any more.

    Here are the settings I am using taken from one of the logs:

    [02:29:58] * video track
    [02:29:58] + decoder: h264
    [02:29:58] + bitrate 200 kbps
    [02:29:58] + frame rate: 23.976 fps -> constant 23.976 fps
    [02:29:58] + filters
    [02:29:58] + Detelecine (pullup) (default settings)
    [02:29:58] + Decomb (default settings)
    [02:29:58] + Framerate Shaper (1:27000000:1126125)
    [02:29:58] + frame rate: 23.976 fps -> constant 23.976 fps
    [02:29:58] + Crop and Scale (1916:800:140:140:2:2)
    [02:29:58] + source: 1920 * 1080, crop (140/140/2/2): 1916 * 800, scale: 1916 * 800
    [02:29:58] + dimensions: 1916 * 800, mod 0
    [02:29:58] + encoder: H.264 (x264)
    [02:29:58] + x264 preset: medium
    [02:29:58] + x264 tune: film
    [02:29:58] + options: b-adapt=2:direct=auto
    [02:29:58] + h264 profile: high
    [02:29:58] + h264 level: 4.1
    [02:29:58] + quality: 18.00 (RF)
    [02:29:58] * subtitle track 1, English (track 0, id 0xff) Text [SRT] -> Passthrough, offset: 0, charset: UTF-8
    [02:29:58] * audio track 1
    [02:29:58] + decoder: English (AC3) (5.1 ch) (track 1, id 0x761100)
    [02:29:58] + bitrate: 640 kbps, samplerate: 48000 Hz
    [02:29:58] + AC3 Passthru
    [02:29:58] * audio track 2
    [02:29:58] + decoder: English (AC3) (5.1 ch) (track 1, id 0x761100)
    [02:29:58] + bitrate: 640 kbps, samplerate: 48000 Hz
    [02:29:58] + mixdown: Dolby Pro Logic II
    [02:29:58] + encoder: AAC (faac)
    [02:29:58] + bitrate: 160 kbps, samplerate: 48000 Hz
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  2. Since you are using CRF encoding the variation in size is to be expected. Some material requires much more bitrate than others to achieve the same quality.

    There are some settings you can adjust to better suit the encoding to the video. x264 has a "tuning" that can be set to animation, film, grain, etc. And, of course, there are dozens of settings in x264 that can be specified individually. I don't know if VidCoder gives you access to all that though.
    Last edited by jagabo; 9th May 2014 at 08:53.
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  3. Member
    Join Date: Apr 2014
    Location: US
    Search Comp PM
    Thanks for the quick reply! Is this due to the quality of the source media?

    I do have it set to Film and adjusted a few other settings. And I have a slightly different Profile set up for DVDs. These settings have, so far, seem to be working for the movies I have converted. The file size difference was more my concern, and I appreciate the feedback.
    Last edited by MikeC58; 9th May 2014 at 09:06.
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  4. Originally Posted by MikeC58 View Post
    Thanks for the quick reply! Is this due to the quality of the source media?
    Many things influence how much bitrate is needed. Basically, the more detail, the more bitrate you need. And anything that causes pixels to change from frame to frame (motion, flickering, billowing smoke/fog, splashing water, grain/noise, etc.) requires more bitrate.

    A movie like 300, with lots of grain, will require a lot more bitrate than a computer animated movie with relatively little detail, no noise, and many identical frames.
    Last edited by jagabo; 9th May 2014 at 09:04.
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