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  1. Member
    Join Date: Mar 2014
    Location: North America
    Search Comp PM
    Hello.

    I would like to convert some video files from mkv to mp4 and vice versa. However, I want to keep the video files identical (also identical file size) which just a different container but it seems that there is no function for it in Handbrake. I read that the output file size varies from source to source but I can't find how to determine which number to put it on in Constant Quality for a file size if I want to keep the file size more or less the same as the source video.

    This is also the case for some video files that I have that are for example in mp4 but have interlace video issues. I want to basically have the same video file in size but with a decomb pass to solve the issues. Again, I don't know how to determine what number I should set it in in Constant Quality. I don't want to it for hours testing setting after setting before I get the file size I am happy with.

    Isn't there some formula one could apply in order to determine what number in Constant Quality should one set in order to get a desired file size?

    Thanks in advance!
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  2. Member
    Join Date: Mar 2008
    Location: United States
    Search Comp PM
    Can't you just remux the video and audio into the new container?
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  3. Member
    Join Date: Mar 2014
    Location: North America
    Search Comp PM
    I'm a bit of a newbie at this so I'm not sure what the best options are.

    Can you remux the video and audio via Handbrake?

    And in regards of applying decomb to the video but still wanting to keep the output file at the same file size or a similar file size (does using decomb usually result in a bigger file size?), what should I do?

    Thanks.
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  4. Originally Posted by runlouierun View Post
    Isn't there some formula one could apply in order to determine what number in Constant Quality should one set in order to get a desired file size?
    No.
    Originally Posted by runlouierun View Post
    And in regards of applying decomb to the video but still wanting to keep the output file at the same file size or a similar file size (does using decomb usually result in a bigger file size?), what should I do?
    Run two passes for the desired filesize/bitrate. Deinterlacing will result in a smaller size for the same quality because interlacing is more difficult to encode. There's no way to run proper compression tests in Handbrake because it doesn't accept AviSynth scripts as input. If it did you could get a better idea of the final size for a given quality. You could do ... say ... 10% of the video and get a less precise idea of what CRF will allow you to reach your desired final size, but that's a very imprecise way to do it.

    Is this interlaced video a movie? Care to put up a small sample for us to have a look? 10 seconds of a scene with steady motion will be plenty.
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  5. Regarding quality based encoding vs. bitrate based encoding:

    With quality based encoding you're telling the encoder what quality you want. It will use whatever bitrate (and hence file size) is necessary to deliver that quality. With bitrate based encoding you're telling the encoder the bitrate (and hence the file size) you want. The encoder will deliver whatever quality it can for that bitrate.

    Different videos require different amounts of bitrate to maintain visual quality. So there's no way to know what the file size will be when you encode with constant quality. And there's no way to know what the quality will be when you encode to a specified bitrate.

    Regarding remuxing:

    Remuxing is the process of taking compressed audio and video out of one container (MKV in this case) and putting it in another (or the same) container. It does not change the audio or video at all. Like taking a cake out of one box and putting it in another. If you do it carefully there's no damage to the cake.
    Last edited by jagabo; 3rd Mar 2014 at 14:23.
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