To understand the basics of video editing, one must consider display frame theory. For this reason, we will often use a fitting comparison in the guide: that of motion pictures and the frames that make up the film.
What is a video format?
We all know that you need a screen, a projector, and a movie to get a movie projection. A sequence of images is printed on the film, translucent as the negatives of the photographs, which in the projection modify the light beam of the projector, allowing only certain parts to pass through, which will generate an image on the screen. Film flows, projected images change rapidly, and a motion effect is obtained.
Let’s go back to digital video.
Let’s say we have a series of images that reproduce a movement (we will see later how the capture phase, or video capture, allows this). These images alone are not enough to show a movie on our PC. In fact, we should be able to tell the machine where these images are, what type they are, how fast they should be viewed, and in what order. For this reason, the format of a clip is defined, that is, a kind of “container”, recognizable by the PC, in which the previous information is attached, in addition to the images.
To recognize a video file format of a clip, you can access the file properties panel or observe the file extension itself (for example, AVI, MPG, QTM, etc … all video extensions).
Each editor chooses the best video format they consider appropriate, depending on how they work, the technology they have available and the end result they want to achieve.
In fact, try to think how much a color image of about 800×600 pixels takes up. So much … too much to see 25 per second (as the theory of optics says) and save them to our HD.
What is a video codec?
This is where the codec (COmpressor DECompressor or better DECoder CODER) comes in, or the software that contains the mathematical procedure through which the images are compressed (often with loss or loss of information) to allow agile management and reproduction correct clip.
In practice, compressed video formats are obtained.
The codec is used both to capture and compress the video from an external source, and to play and process the video once it is stored on the hard drive. It could be compared to a kind of very fast Winzip that, if necessary, compresses and decompresses the images of a film.
It is useless to dwell on how a codec manages to make a noticeable decrease in the space occupied by images, reducing the loss of quality to a minimum (sometimes surprisingly!) What little indication to say which is the best video codec or the best compression Of video . The answer is always the same: it depends on what you want to achieve (and, similarly, what is the best video format is a question that has multiple answers).
The important thing is that these codecs are available to us, there are many of them and each one has peculiar characteristics that suggest its working environment.
We suggest downloading the K-Lite Codeck Pack (often also abbreviated as Klite) which contains an important collection of useful and cross-cutting codecs, tools, formats and filters.
Structure of a video format
Hardware codec and analog capture
Until recently, analog capture cards (especially M-Jpeg) were almost all equipped with a proprietary chip that allowed smooth, lossless capture as it took the computer’s processor out of compression work (it’s this chip that kept the price of the cards high).
The hardware codec is still software, but it interacts with this chip by letting the system know that it exists and that it can do the job instead of the CPU.
Without the codec installed, the card chip is useless, whereas if only the software codec is installed, the PC processor may be able to do the compression job, but this in particular cases.
Entry-level PCs are still powerful, and often analog acquisition cards only have one analog-to-digital conversion chip, while the processor does the conversion. In some cases, it is even possible to capture with very complex and elaborate software codecs like DivX or Xvid.
It is clear that choosing the hardware codec is always recommended, as in the case of the MPEG2 capture which requires a lot of resources.
