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Thread: Compressing 129GB of MKV Files

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    Compressing 129GB of MKV Files

    Hi there! Feel free to delete this thread if it's in the wrong location/or if it breaks any rules.

    Anyway. I'm running out of space on my hard drive, and the biggest thing on my drive is my Stargate SG-1 show, and it's taking up 129 gigs.

    How would I go about compressing the show as much as possible without losing video/audio quality?
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    You cannot compress a video more than, I think, 10%. The best things here is that you re-encode them to lower bit rates and If you are lucky, you won't lose much quality. It is very very time consuming. The fastest is to convert each episode audio to ogg vorbis because this will lower the size of audios to 40% and won't budge its quality much. You may even get to overall 100GB.

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    Phoenix (22nd October 2016)

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    Wow, that stinks. Thanks for the info!

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    Administrator Shelwien's Avatar
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    1. Split mkv files into tracks with mkvextract
    2. There're ways to re-encode/recompress audio tracks
    3. There're ways for lossless recompression of video too:
    http://encode.su/threads/2285-H264-L...-recompression
    http://encode.su/threads/1111-Ocarin...deo-compressor
    4. If nothing else helps, you can try getting these 10% with something like http://freearc.org/research/SREP.aspx

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    Bilawal (24th October 2016)

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    If you've got really desperate on disk space, to degree you're going to be ok with some loss of visual quality and your source files aren't looking awful, most realistic and efficient option would be to try to re-compress (transcode) your videos. But you have to understand this process is lossy and could make videos to look worse. Yet, it could happen original files had good margin, so maybe you could squeeze extra without reaching "pain thershold". When you encode video, you can select bitrate you target, so you have complete control over file size. Obviously, if you make it too small its quality is going to be crap.

    A bit less obvious way is to examine data further. Say, there could be, say, PCM audio track or maybe 5.1 audio you do not need on system only capable of 2-channel stereo. So it could be viable idea to compress/recompress/downmix audio track. Some files could have multiple tracks, say, different angles of view or different languages. Removing things you think you do not need could save quite some space for sure. But it takes some understanding of what your data are. Sometimes there could be low hanging fruit. Say, I've seen really stupid files coming with PCM (aka uncompressed samples) audio track, so audio track took more space then video track! (normally video takes considerably more space).

    If your CPU is powerful enough you may want to explore modern, "highly efficient" codecs like VP9 and HEVC (e.g. x265). Improving codecs is all about attempt to reach appealing video quality while keeping bitrate low. But it usually implies more complicated and slow encoder, that's where one may want powerful CPU: waiting for a while may wasn't part of the plan. Though certain groups of ppl like these who created your files historically ran encodings overnight, to afford decent quality while file size is reasonable.

    The downside is: to get decent result where your files are small yet looking good, you'll have to learn some basics, get familiar with codec of your choice and its tunables and after all it could be trial-and-error approach. But once you get some feeling of the tool and understanding of your data, you could do something pretty close to magic. Eventually one could learn to get low-hanging fruits with really epic results, like reducing file size, say, 5x without being able to spot visual difference (e.g. on videos captured by cameras, they can't afford decent analisys in real time so they just throw more bandwidth to get sane quality). At very least, you almost certainly want 2-pass encoding and maybe even further tune codec to favor quality over speed, so you could get your files smaller without giving up too much of video quality. You could also take a look on more specialized forums like doom9.org (which is inclined on DVDs, but since backing up DVDs usually implies recompression of ancient and inefficient MPEG-2... get the idea).

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    Bilawal (24th October 2016)

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    Member SolidComp's Avatar
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    The best way to compress video is to convert it to a more efficient format. Matroska (MKV) is just a container – what codec did you use for the video? If it's MPEG2 or MPEG4, you can probably save a lot of space by converting it to VP9 with FFmpeg. If you're on Windows, Mac, or Ubuntu, Handbrake is a good tool for conversion too.

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    Bilawal (24th October 2016)

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    Have you checked the price of drives lately? 500GB-2TB drive are not that expensive really. You could consider getting a bigger drive instead of smaller files.

    Sometimes the easy solution is to spend some money.

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    i propose relocation to russia. you need to pay only once for a lifetime license to grab

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