As digital video involves far more data such as moving visuals and sound as opposed to a simple word processing document or even a photograph, it inevitably takes up far more room on your hard drive. Even if you intend storing video files on an external drive, you’ll still need to work with them on your hard drive initially and this is why video compression is so important as it involves making files smaller so that they can be stored more practically.
Doesn’t Compression Mean Losing Quality?With digital video, the aspects of the compression don’t end up affecting the quality that we, as viewers, can perceive. A couple of examples are where there are literally billions of colours but variations in shades are so subtle that to us with the naked eye, we cannot comprehend the tiniest changes in shade and therefore not all of that data is needed, hence it can be compressed.
Likewise, although an object may be present in a scene for a minute or even longer, an example being a static table in a room, it’s not necessary to keep all the data contained in each particular frame as the table is going nowhere. So, in effect, compression is really a function of getting rid of all the saved data that has been captured during filming which, to the capabilities of our eyesight as viewers, we don’t really need as we wouldn’t be able to perceive any difference even if it wasn’t compressed.
The Best Way Of Maximising CompressionStandard digital camcorders tend to compress data at a ratio of 5 to 1, although there are many formats which enable data to be compressed at a far higher ratio. The key is to use as much compression as possible and then stop when you spot with your own eyes that the quality is starting to diminish and then, simply to push the compression back a bit until quality is restored.
And, it really is a case of there not being a standard fixed rate of compression which you should be aiming for. Some videos look fantastic when tightly compressed yet the same amount of compression on others looks awful.
OptionsIt is also necessary to determine which compression format tool works best for your specific project. The likes of DivX has become increasingly popular for compressing full length feature films whilst other film makers use MPEG-4 which has translated very well into the use of compression for the likes of viewing shorter clips on hand held PCs, personal music players which are now capable of showing visual clips and even longer feature length movies. Some of the video clips you can get on mobile phones will also have been compressed using MPEG-4 whilst other applications still use MPEG1 and MPEG2.
Some file formats use up more bitrates per second with the resulting quality exactly the same so there is no real tried and trusted answer to the solution of video compression for your own specific project and upon what media platform you intend to view it. Ultimately, it’s a case of trying out different compression formats and seeing what works best for your particular project, reading up on the subject and speaking to others working in the industry for their advice based upon your specific projects and needs.