Deal with digital video formats
With the advent of the first computers, and with them digital storage devices, a gradual transition from analog to fully digital technology began. With it, we got a number of undeniable advantages (ease of copying and processing) and a big digital data storage problem. How to avoid quality loss when processing video, we will tell you in our article.
How much does the video weigh
PAL or SECAM video is a sequence of images displayed at 25 frames per second. A digital frame contains 720×576 pixels, that is, 414 thousand 720 elements (pixels). Each point can be one of 16.7 million colors and occupy 3 bytes on the computer. Consequently, one frame is approximately 1.2 MB. At the standard frequency, we get a figure of about 30MB per second, that is, storing just one hour of video (along with sound) without compression will cost 107GB. It seems intimidating, but it is already acceptable now.
But the progress of the video doesn’t stop. The highest possible quality is now achieved in HDTV (high definition TV), this format implies a resolution of 1920 x 1080 pixels, that is, all things being equal, a series of frames calculated for one second will already take 148 MB (521 GB per hour).
In order to avoid such volumes of stored video and waste of computing resources, as well as to be able to distribute video clips, various video compression methods have been developed. The achievements in the development of digital technology achieved over 15 years are actively used in everyday life, in video broadcasts, home devices (video cameras, DVD players) and on the Internet. Depending on the type of codec, you can achieve different compression rates and different “weight” of the finished film.
How compression occurs
Unlike universal archivers (such as WinRar or WinZip), video compression occurs with some loss, the amount of which depends on the selected codec. This is due to the fact that the algorithms of conventional filing cabinets practically do not compress the video information (as well as the sound). Modern compression algorithms use extensive logical analysis of the video to extract duplicate fragments between frames and reduce the size of the final file. When played, the compressed information is “expanded” and then displayed to the user. On a low-power computer, it can take a long time to break down images compressed with some codecs.
Various codecs are used to compress video
Most popular codecs
The most common codecs today are the MPEG family. It was based on the compression of photographs. We are all familiar with compact images with the JPG extension, and many can even distinguish a highly compressed image (with a cubic structure) from a high-quality one (with the naked eye, comparable to the original). The anatomical features of the human eye allow it to imperceptibly compress the image ten times using the JPEG encoder.
Strong compression
Maximum quality
In the given examples, you can see which artifacts, so-called cubes, appear in the photo that are incorrectly compressed (with a high compression ratio) and their absence in the photo with the correct compression. Such loss of quality with high compression by most codecs, including JPEG, is irreversible.
