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title = 'Converting big videos'
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summary = '''I am subscribed to a few mailing lists and I stumbled across
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a big video file in one of them recently. Here is a small command-line
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command using **ffmpeg** that cut its filesize in half.'''
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date = '2023-10-01T10:37:00+0200'
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#lastmod = ''
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categories = [ 'computerstuff' ]
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tags = [ 'openbsd', 'freebsd', 'linux', 'command-line' ]
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+++
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I don't like big mail attachments but when I see them I try to reduce their filesize
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because I think it should be possible to send pictures with good quality but with reduced
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filesize.
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{{< alert >}}
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Whenever I talk about filesizes or video sizes in this post, I want to
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send them via email. You can of course have big files with high bitrates,
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but forcing the mail recipient to download those in his email client is
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just not okay IMHO.
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{{< /alert >}}
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For this I inspect images and videos with some basic commands.
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## Inspecting the video file
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```console
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$ ll Video.MOV
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-rw------- 1 dominic dominic 10.7M Sep 23 19:05 Video.MOV
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$ file Video.MOV
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Video.MOV: ISO Media, Apple QuickTime movie, Apple QuickTime (.MOV/QT)
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$ ffmpeg -i Video.MOV
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ffmpeg version 4.4.4 Copyright (c) 2000-2023 the FFmpeg developers
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built with OpenBSD clang version 13.0.0
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configuration: --enable-shared --arch=amd64 --cc=cc --enable-debug --disable-stripping --disable-indev=jack --disable-outdev=sdl2 --enable-fontconfig --enable-frei0r --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libdav1d --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmp3lame --enable-libopus --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-nonfree --enable-openssl --enable-libvidstab --extra-cflags='-I/usr/local/include -I/usr/X11R6/include' --extra-libs='-L/usr/local/lib -L/usr/X11R6/lib' --extra-ldsoflags= --mandir=/usr/local/man --objcc=/usr/bin/false --optflags='-O2 -pipe -g -Wno-redundant-decls'
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libavutil 56. 70.100 / 56. 70.100
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libavcodec 58.134.100 / 58.134.100
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libavformat 58. 76.100 / 58. 76.100
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libavdevice 58. 13.100 / 58. 13.100
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libavfilter 7.110.100 / 7.110.100
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libswscale 5. 9.100 / 5. 9.100
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libswresample 3. 9.100 / 3. 9.100
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libpostproc 55. 9.100 / 55. 9.100
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Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Video.MOV':
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Metadata:
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major_brand : qt
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minor_version : 0
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compatible_brands: qt
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creation_time : 2023-09-23T16:11:17.000000Z
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com.apple.quicktime.artwork: <20><>
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com.apple.quicktime.is-montage: iMovie
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Duration: 00:01:53.23, start: 0.000000, bitrate: 795 kb/s
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Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 94 kb/s (default)
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Metadata:
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creation_time : 2023-09-23T16:11:17.000000Z
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handler_name : Core Media Audio
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vendor_id : [0][0][0][0]
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Stream #0:1(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p(tv, bt709), 568x320, 693 kb/s, 30 fps, 30 tbr, 600 tbn, 1200 tbc (default)
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Metadata:
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creation_time : 2023-09-23T16:11:17.000000Z
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handler_name : Core Media Video
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vendor_id : [0][0][0][0]
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encoder : H.264
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At least one output file must be specified
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```
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## Converting to a smaller filesize
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With default values (for bitrates). Takes about 12 seconds and
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creates a 4.4MB big file. I also strip metadata out of the videos, usually.
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```console
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$ ffmpeg -i Video.MOV -acodec aac -vcodec h264 -map_metadata -1 newvideo-default.mp4
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```
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Another approch would be to specify the bitrates. You probably have to “play” with
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these values. For this example I chose 64k for audio and 300k for video. Note, that
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the filesize is actually bigger than the example above (with default values). This
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took about 16 seconds but creates a file of 5.0MB.
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```console
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$ ffmpeg -i Video.MOV -acodec aac -vcodec h264 -map_metadata -1 -b:a 64k -b:v 300k newvideo-64k-300k.mp4
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```
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## Also convert the video size
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When we inspected the file above we notices a video size of 568×320.
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We will reduce this now to 240 on the shorter side and we will get a
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new file that is 3.2MB big.
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```console
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$ ffmpeg -i Video.MOV -acodec aac -vcodec h264 -map_metadata -1 -filter:v scale=-1:240 newvideo-default-resized.mp4
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```
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We can improve this by reducing the audio bitrate to 32kb/s (going
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further down did not reduce the file much).
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```console
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$ ffmpeg -i Video.MOV -acodec aac -vcodec h264 -map_metadata -1 -filter:v scale=-1:240 -b:a 32k newvideo-default-resized-32k.mp4
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```
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Another look into the last converted file:
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```console
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$ ffmpeg -i newvideo-default-resized-32k.mp4
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ffmpeg version 4.4.4 Copyright (c) 2000-2023 the FFmpeg developers
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built with OpenBSD clang version 13.0.0
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configuration: --enable-shared --arch=amd64 --cc=cc --enable-debug --disable-stripping --disable-indev=jack --disable-outdev=sdl2 --enable-fontconfig --enable-frei0r --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libdav1d --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmp3lame --enable-libopus --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-nonfree --enable-openssl --enable-libvidstab --extra-cflags='-I/usr/local/include -I/usr/X11R6/include' --extra-libs='-L/usr/local/lib -L/usr/X11R6/lib' --extra-ldsoflags= --mandir=/usr/local/man --objcc=/usr/bin/false --optflags='-O2 -pipe -g -Wno-redundant-decls'
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libavutil 56. 70.100 / 56. 70.100
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libavcodec 58.134.100 / 58.134.100
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libavformat 58. 76.100 / 58. 76.100
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libavdevice 58. 13.100 / 58. 13.100
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libavfilter 7.110.100 / 7.110.100
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libswscale 5. 9.100 / 5. 9.100
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libswresample 3. 9.100 / 3. 9.100
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libpostproc 55. 9.100 / 55. 9.100
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Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'newvideo-default-resized-32k.mp4':
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Metadata:
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major_brand : isom
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minor_version : 512
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compatible_brands: isomiso2avc1mp41
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encoder : Lavf58.76.100
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Duration: 00:01:53.24, start: 0.000000, bitrate: 140 kb/s
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Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 426x240, 100 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
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Metadata:
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handler_name : VideoHandler
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vendor_id : [0][0][0][0]
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Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 31 kb/s (default)
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Metadata:
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handler_name : SoundHandler
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vendor_id : [0][0][0][0]
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At least one output file must be specified
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```
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## How to find the best values
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The best option is probably to get routined. Convert some videos and look what
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changes (video and audio quality, filesize). Also try to trim them if you need to.
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Have a look at the [manpages of ffmpeg][1] (switches `-t`, `-to`, `-ss`).
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[1]: https://ffmpeg.org/ffmpeg.html
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I guess a short video where someone is talking and explaining something does
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not always need high bitrates. This is like a slideshow where someone is talking
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in the background.
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If you want to share music you might use higher bitrates. The classic mp3 files
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sounded quite good with 192kb/s or even 320kb/s but I think 128kb/s should
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also be fine. For aac files I'd probably try 96kb/s first and then increase or
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decrease on another run and look if the filesize improves.
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It basically makes no sense reducing much of a bitrate if the filesize stays nearly
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the same in the end (as long as you can't see or hear much difference).
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## Some values for reference
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The filename suggest the used bitrates and options.
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```console
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$ ll Video.MOV newvideo-*
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-rw------- 1 dominic dominic 10.7M Sep 23 19:05 Video.MOV
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-rw-r--r-- 1 dominic dominic 5.0M Oct 1 09:48 newvideo-64k-300k.mp4
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-rw-r--r-- 1 dominic dominic 6.4M Oct 1 09:40 newvideo-64k-400k.mp4
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-rw-r--r-- 1 dominic dominic 1.8M Oct 1 10:04 newvideo-default-resized-16k.mp4
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-rw-r--r-- 1 dominic dominic 1.8M Oct 1 10:03 newvideo-default-resized-24k.mp4
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-rw-r--r-- 1 dominic dominic 1.9M Oct 1 10:01 newvideo-default-resized-32k.mp4
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-rw-r--r-- 1 dominic dominic 3.2M Oct 1 09:54 newvideo-default-resized.mp4
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-rw-r--r-- 1 dominic dominic 4.4M Oct 1 09:43 newvideo-default.mp4
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```
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```console
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$ ls -l Video.MOV newvideo-*
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-rw------- 1 dominic dominic 11254505 Sep 23 19:05 Video.MOV
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-rw-r--r-- 1 dominic dominic 5290645 Oct 1 09:48 newvideo-64k-300k.mp4
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-rw-r--r-- 1 dominic dominic 6705317 Oct 1 09:40 newvideo-64k-400k.mp4
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-rw-r--r-- 1 dominic dominic 1844227 Oct 1 10:04 newvideo-default-resized-16k.mp4
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-rw-r--r-- 1 dominic dominic 1869904 Oct 1 10:03 newvideo-default-resized-24k.mp4
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-rw-r--r-- 1 dominic dominic 1991368 Oct 1 10:01 newvideo-default-resized-32k.mp4
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-rw-r--r-- 1 dominic dominic 3382468 Oct 1 09:54 newvideo-default-resized.mp4
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-rw-r--r-- 1 dominic dominic 4647129 Oct 1 09:43 newvideo-default.mp4
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```
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## Related content (optimizing images)
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I've created a similar post for images in 2020:
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[Optimizing PNG images]({{< ref "2020-01-20-optimizing-png-images/" >}})
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(there is also some info on JPG files).
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