What is Video Compression and What is it Used For?
Have you ever had to delete pictures or videos of precious memories due to a lack of available storage on your phone or computer? Video compression offers a solution to this problem by significantly decreasing the size of the files in an image. Similar to maximizing the space in your suitcase while packing for a vacation or overnight getaway, video compression optimizes all of the space on your storage device in the most effective way possible.
Video compression refers to the process of reducing the total number of bits needed to represent a given video sequence or image. It is most commonly executed by a program formula or algorithm that calculates the best way to adequately shrink the size of the data. The reduction in data that results from compression carries benefits such as lower bandwidth requirements and smaller storage requirements for a clip of video content.
Video compression usually involves an omission of information not considered to be absolutely necessary to the viewing of a clip of video content. An effective compression codec will make the video files smaller and more manageable without sacrificing the quality of the images displayed. Moreover, significant hardware and overhead costs will not be needed to compress large amounts of video. As a general rule, the more aggressive the compression, the greater the savings in the transmission bandwidth and storage space. However, this is done at the expense of video quality.
How does video compression work?
There are two primary ways to compress the data in a video clip: interframe compression and intraframe compression. Intraframe compression takes each individual frame of the video and compresses the files in a manner similar to the way in which JPEG is used to compress a still image. Conversely, interframe compression slightly compresses the image and ensures that every frame is complete. The decision to implement interframe as opposed to intraframe compression will be contingent on your specific video needs.
For instance, video codecs use interframe compression with the goal of getting the most significant compression possible. The basic idea behind this choice is that because videos consist of multiple still frames, interframe compression will look at each individual frame, compare it to the previous frame, and then stores only the data that has changed. Alternatively, interframe compression does come with limitations, as frames skipping as the video is being imported to another source would cause issues with the image being projected.
Why is video compression needed?
Video compression is essential when recording and in turn saving any form of surveillance or security footage because compression changes the files into a smaller format. This maximizes hardware space and allows for more videos to be saved on a given hard drive or storage device. Moreover, video compression allows users to store longer and higher quality videos on their hard drives, as these videos would quickly eat up memory if not compressed. There are 3 primary formants for video compression:
- H.264 compression – This format works by evaluating small images of data together simultaneously while also removing duplicates and is widely considered to be the most efficient way to compress video files among industry professionals.
- MJPEG compression – This format evaluates each individual frame in a video and treats the frame as an individual JPEG image.
- MPEG4 – This is the oldest video compression format and has largely been made obsolete with the development of the H.264 format.
Compression and bit rate
After a computer or camera has finished with the compression process, the file size will equal the bit rate of X seconds of video. Theoretically speaking, the higher the bit rate the more data stored in a particular file, which by extension results in a higher quality compression. However, there are other mitigating factors that influence this process. For example, as different cameras use different codecs to compress data, the compression algorithm used on the data will differ from manufacturer to manufacturer. Generally speaking, there are two general categories for compression algorithms, lossy and lossless.
Lossy compression doesn’t quite provide an exact pixel for pixel match of an image when compressed but offers much higher compression ratios than lossless compression will. Contrarily, lossless compression means that each pixel is exactly the same as the original and in effect cannot be lost. Which codec and compression algorithm you choose will depend on the specific needs of your company or organization. Some high-end cameras on the market today will offer codecs that provide quality images at the same bit rate. On the other hand, other cameras will use a less aggressive codec altogether in order to maintain the most pristine image quality possible.