How to compress a video

Big videos and small attachment limits can stop a project in its tracks – here’s how video compression can help.

Sharing videos

Technology is a wonderful thing, but there are still some things that can make even the most tech-savvy person get a little anxious. Getting a high-quality video from your team to a client can be one such topic of concern – after all, videos can be bulky files at the best of times.

What is video compression?

Video compression is a way of shrinking your video file size. Unfortunately, almost all methods of file sharing, from email to instant messaging, have some sort of file size limit. That means your video either won’t fit into your message, or if it does, your recipient can look forward to a lengthy download period on their end. Essentially, compressing your video cuts a chunk off the size needed by your file, though it usually means overall quality takes a hit, too. Depending on the original size, this quality loss may not even be noticeable, but that all depends on how small you need your video size to be.

What’s a byte?

A byte is a unit of measurement used for digital files. You don’t need to go deep into computer terminology to know how to compress video files, but a basic understanding of these units can help you understand just how big your file is. Generally, you will see files measured in kilobytes, megabytes, gigabytes and terabytes, which break down as follows:

  • Kilo: 1024 bytes
  • Mega: 1024 kilobytes
  • Giga: 1024 megabytes
  • Tera: 1024 gigabytes

So, essentially, if your file is in the gigabyte range, you’ll want to get it down to the megabytes.

What’s a codec?

If you start looking into the technical side of video management, you’ll soon come across codecs. Codecs are the code used to compress your video: they essentially shrink your file down for storage and then decompress them again when you’re ready to view them. Codecs usually work automatically within the program of your choice, and, generally speaking, you don’t need to know much about them to be able to compress a video as your software will do it for you. All you really need to know is that, without codecs, your file would be at least three to five times larger in size.

If you’re confronted with a choice of which codec to go for, it might be helpful to know the following types of codec:

  • MPEG: One of the most widely-used codes, MPEG and its derivatives including MPEG-1 and MPEG-4 result in high quality video playback even after compression.
  • ProRes: A codec used in software such as iMovie, ProRes, as the name implies, gives fantastic colour resolution.
  • WMV: You’ve no doubt come across this one before if you are a Windows user. WMV is claimed to provide better quality than MPEG-4 and if you are using Microsoft video editing software, chances are this is the codec it will opt for.

Is AVI a codec?

No, an AVI is a container which dictates your video's file extension. Containers are like envelopes that hold the codecs. So while an AVI and MP4, for example, are both file types/containers, they are not codecs in themselves. They do still make a difference, though. MP4s usually come up smaller than AVIs due to a better compression rate.

How big is a video file?

The precise number of bytes needed for your file will depend on several factors, including:

Video formats

Video types can impact the overall size and quality. The following are all video file types:

  • MP4
  • AVI
  • FLV
  • MOV
  • WMV

Without getting too complex, some file types offer better codecs, that is, the process used to compress your video. An MP4, for example, if converted to an FLV file, will be a larger file overall, as the codecs of a FLV are less efficient and result in less compression/file shrinkage.

Video length

A video of one minute will obviously be smaller than a video of one hour – though, again, your choice of file type can also impact the ratio between video length and file size.

Video quality

Frame rate and resolution impact file size. Frame rate, or FPS (frame per second) also effects video quality, with HD video using a minimum of 24 FPS. The more frames you have, the more detail you have, and the larger your file will become. Videos shot in 60, 120 or even 240 FPS can be slowed down to 24 or 30 FPS for slow motion videos. They can also be left unaltered, making for clips with life-like smoothness.

If your video is 480p, then it is designed to be a smaller overall display at 852x480 pixels. A 720p video enters the realms of HD at 1280x720. A high resolution doesn’t necessarily mean the highest level of quality, it just denotes how large an area the video has been created to fill, not a guarantee that it will fill that space with crystal clear detail.

If your video is 480p, then it is designed to be a smaller overall display at 852x480 pixels. A 720p video enters the realms of HD at 1280x720. A high resolution doesn’t necessarily mean the highest level of quality, it just denotes how large an area the video has been created to fill, not a guarantee that it will fill that space with crystal clear detail.

For a 1-minute video:

  • Ultra HD or 4K (3840x2160): 2 GB file size
  • 2K resolution (2048x1080): 430 MB file size
  • 1080p or Full HD (1920x1080): 403 MB file size

How does video compression work?

Video compression occurs by removing repetitive images and sounds as determined by the codec algorithm. To the human eye, this loss is hardly noticeable. Think about how a Hollywood film goes from cinema screen size to a DVD, able to play on any home TV without lag. You’ll only start to see compression really wreak havoc on display quality if you want to shrink a file down to a tiny file size while maintaining resolution – this is when things start getting 'pixely', 'grainy' and generally not viewable.

How can I compress a video?

To successfully compress a video file, you will need dedicated software such as iMovie for Mac or Windows Video Editor for Windows. Alternatively, you could send your video in a ZIP compressed file, but this will require your recipient to download it on their end.

All these programs require from you is to open your video, usually by clicking 'open' or 'import' and then exporting them which converts them to a new file type. Most video editing programs will let you choose your resulting file format including MP4, AVI, MOV and WMV.

How do I compress a video with Dropbox?

Luckily, you don’t need to worry too much about bytes and formats to successfully send a long video with Dropbox. Dropbox supports the following video file formats, to name a few, and will automatically compress them for viewing on your device, with the option to download them in full quality should you so wish:

  • AVI
  • MKV
  • MP4
  • MPG
  • MOV
  • WMV
  • OGV
  • 3GP

And, as long as your file size is below 50 GB, the preview will display as a sleek video. You can send videos from your phone, desktop or tablet, shareable via link added to an email, text or chat, your recipients don’t even need a Dropbox account and can view the video without downloading them. Plus, there is no size limit on the video you can upload, so no need to panic about compressing and re-compressing your file.

Up your efficiency with Dropbox

Dropbox makes it effortless to share files securely in real time. Give access to shared folders for instant sharing, without time-consuming downloading – you can send the sharing link to anyone, whether they have a Dropbox account or not. That means nothing can hold you back if you’re working on a creative video project, sharing a presentation or you just want to send a funny video to a friend.

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