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I'm working with video editing for years but suddenly I've stumbled upon an issue that I can't seem to figure out. I have many video files in .mkv, and I need to edit them in Sony Vegas - hence, I need to convert them. Files are 720p resolution. When I convert them though, the size difference is quite incredible - from 350MB to 1GB per file. I don't have enough space on my computer to work on such huge files, but I still need to edit them in Vegas. I've been reading about conversion, but this continues to be a confusing topic to me. From what I understood the size difference comes from bit rate change and the general settings of conversion.

Can anyone explain to me, in simple words if possible, how to reduce the size when converting? I'd love for it to be at least half the size (0.5GB at most). Maybe there is a way to keep it the same size as the original file, or would there be too much quality loss? Is the only way of reducing file size is quality loss? Maybe I could use another file extension or different settings?


edit:MediaInfo

General
Format                                   : Matroska
Format version                           : Version 4 / Version 2
File size                                : 351 MiB
Duration                                 : 46mn 26s
Overall bit rate                         : 1 056 Kbps
Writing application                      : mkvmerge v7.9.0 ('Birds') 64bit
Writing library                          : libebml v1.3.1 + libmatroska v1.4.2

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L4
Format settings, CABAC                   : Yes
Format settings, ReFrames                : 8 frames
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 46mn 25s
Bit rate                                 : 998 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate mode                          : Constant
Frame rate                               : 23.976 (24000/1001) fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.045
Stream size                              : 331 MiB (95%)
Writing library                          : x264 core 146 r2538 121396c
Encoding settings                        : cabac=1 / ref=8 / deblock=1:-1:-1 / analyse=0x3:0x133 / me=umh / subme=9 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=2 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=12 / lookahead_threads=1 / sliced_threads=0 / nr=0 / decimate=1 / 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=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=60 / rc=2pass / mbtree=1 / bitrate=998 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=1:1.00
Default                                  : Yes
Forced                                   : No

Audio
ID                                       : 2
Format                                   : AAC
Format/Info                              : Advanced Audio Codec
Format profile                           : HE-AAC / LC
Codec ID                                 : A_AAC
Duration                                 : 46mn 26s
Bit rate                                 : 56.0 Kbps
Channel(s)                               : 2 channels
Channel positions                        : Front: L R
Sampling rate                            : 48.0 KHz / 24.0 KHz
Frame rate                               : 23.438 fps (1024 spf)
Compression mode                         : Lossy
Delay relative to video                  : 31ms
Stream size                              : 18.6 MiB (5%)
Default                                  : Yes
Forced                                   : No
  • What does Mediainfo say for one of the MKVs? Select View -> Text mode and paste that readout. – Gyan Jun 19 '16 at 10:46
  • @Mulvya, ok, updated! :) – user15924 Jun 19 '16 at 11:03
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Using ffmpeg, a free command-line tool, you should be able to run

ffmpeg -i input.mkv -c copy input.mp4

Vegas might not load the audio, since it's HE-AAC. In which case, run

ffmpeg -i input.mkv -c:v copy input.mp4

Both the commands simply copy the video stream into a MP4, so there's no recompression. The 2nd command recompresses the audio, for compatibility's sake.

  • wow, so is it like, it's a compression over a command line? :O I've never heard of it before, sounds super exciting to me! Usually I've just been using Freemake Converter. So after doing this, the files should be saved as .mp4 files (with audio separated)? – user15924 Jun 19 '16 at 15:40
  • *conversion, I mean. not compression – user15924 Jun 19 '16 at 15:50
  • Yes, you will get MP4 files. The audio won't be separated. I'm not sure if the audio codec in the MKV is compatible. So, if Vegas doesn't load the audio in the MP4 generated by the first command, then try the second. – Gyan Jun 19 '16 at 16:17
  • 1
    Try ffmpeg -i input.mkv -crf 18 -profile:v main -c:a copy input.mp4 – Gyan Jun 19 '16 at 17:28
  • 1
    Increase the CRF value. Try 21. – Gyan Jun 19 '16 at 19:56

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