Compression is necessary if you want to share your videos on the internet because it reduces the amount of data that is needed to stream or send the video to the viewer. If you understand the basic terms you’ll be able to use any program to compress video files to fit your needs.
SUMMARY
1. Open your raw video file in a video editing program.
2. Export the video.
3. Select the file and video format.
4. Select the bit rate and the resolution.
5. Adjust the keyframe and frame rate.
6. Select the encoding mode and set your audio options.
THE TERMS INVOLVED
1
Compression. This is the entire process of changing a raw video file into a format that takes up less storage and is easier to computer and devices to play. Raw, uncompressed video is typically filmed with 24 or 30 frames per second. That means that every second, 24 or 30 still images are displayed to give the illusion of movement. Because the images are so closely linked, not everything in the image moves from frame to frame. Compression stores just the parts of each frame that change as opposed to storing every entire frame.
2
Codec. This is a method that your computer uses to decide on the amount of change that occurs between frames. The word “codec” is a combination of “encoder” and “decoder”. It takes the raw video, encodes it into a smaller package, and likewise can unpack and play the video.
3
Keyframe. This is a reference frame. The codec will determine a keyframe every few frames. This is the base frame for the next few frames of change. Your keyframe interval will have a large impact on the size of your finished file. Lots of keyframes will make the file larger but higher in quality. Infrequent keyframes will leave lots of artifacts.
4
Artifacts. These are blocky pieces of the image that are the result of the keyframe not being updated correctly. The lower the quality of the compression, the more artifacts that will appear.
5
Bit rate (or data rate). This is the amount of data that each second of video will use. Typically, this is measured in kilobits per second. Bit rates can be either Constant or Variable. A constant bit rate stays the same throughout the video, which can lead to larger video files. A variable bit rate changes depending on the amount of action on the screen, which will lead to smaller files.
Variable bit rates can decrease quality if the bit rate does not change dynamically enough with the video. Experiment with both bit rates to find a balance between size and acceptable quality.
6
Frame rate. This is the number of frames per second. Videos are typically shot in 24 or 30 frames per second. It’s recommended to keep the frame rate the same as the original raw video, otherwise, playback will look choppy and the audio may not sync properly.
7
Resolution. This is the size of the outputted video. It is measured in pixels, “width” x “height.” Some common resolutions are:
854 x 480 (Full Wide Video Graphics Array, “480p”)
1280 x 720 (High Definition, “720p”)
1920 x 1080 (Full High Definition, “1080p”)
3840 x 2160 (4K Ultra High Definition, “4K”)
4096 x 2304 (Full 4K Ultra High Definition)
WHEN COMPRESSING FOR YOUYUBE AND VIMEO
1
Understand why you need to compress. Raw video files, especially HD video, can run several gigabytes in size. While you can upload large files to YouTube and Vimeo, this can also take a very long time. Also, these services will compress your file once it is uploaded, and often the results are not very high quality. Compressing your video yourself allows you to control both the size and the quality.
2
Open your raw video file in a video editing program. There are free solutions available online, as well as professional products such as After Effects, Final Cut, and more. The specific menus will vary between programs, but the settings are universal across all programs.
3
Export the video. In order to start the compression process, you will need to export the video. This will convert the video into a format that is playable on all systems and devices, including formats supported by YouTube and Vimeo.
4
Select the file format. The file format will change depending on what you plan on doing with the final file. Most systems and devices will play MP4 files, making it the most universally accepted file type. This includes game systems like the PlayStation 3.
5
Select the video format (codec). H.264 is the most widely used codec and is supported by the most systems. This is the preferred codec for uploading videos to be streamed online. HD (High Definition) video should be encoded in H.264.
6
Select the bit rate. For SD (Standard Definition, resolutions of 480p or lower) video, use a bit rate between 2,000-5,000 kbps. 720p video should have a bit rate between 5,000-10,000 kbps. 1080p video should have a bit rate of 10,000-20,000 kbps.
7
Select a video resolution. Try to keep this the same as your raw video.
Some streaming websites will add in their own resolution options after the uploading process.
8
Adjust the keyframe and frame rate. Encode your video in the same frame rate that you recorded it in. If you recorded above 30 frames per second, encode in half that (for example, a 60 FPS video would be encoded at 30 FPS). Keep the keyframe the same as the frame rate.
9
Select an encoding mode. In general, go for multi-pass encoding. This will take longer than a single-pass encoding, but will result in a noticeably higher-quality video.
10
Set your audio options. Choose AAC-LC as the audio format, as this has the widest support and the best quality. For data rate, select 320 kbps. Your output sample rate should be 48.000 kHz
