With this post (the first of a collection that we hope will be to your liking) we intend to give space in this blog to the possibilities multimedia under the wonderful world of free software with the free system par excellence. Section in which new applications are emerging every day and existing ones are improved to such an extent that it is completely versatile to be able to work, even professionally, with said applications.
In this post we will focus on the basic concepts to keep in mind when we start in the world of video edition as a starting point for the rest of the articles that will follow
The videos are nothing more than sequences of images at a minimum speed so that the movements appear continuous.
There are three technical aspects that we must know when editing videos, these are: Resolution, Aspect and Frame Rate (frames).
- Resolution: It is the size or dimension of the images (photos) that make up our video. In the era of HD (High Definition) video, the value they give us is the height of these images, which would be the “Y” axis in pixels. In the past, before high definition video, resolution was indicated by the x-axis.
- Appearance: It is the way the video will have, currently, in the era of HD video, videos are a rectangle with a ratio of 16/9, this means that for every 9px in height, it will be 16px in width. Formerly the most used aspect was that of 4/3 and when in these almost square monitors it was broadcast in 16/9 they did so by cropping the image with black bands at the top and bottom of the image.
- Frames per second or frames (fps): It is the speed with which the images pass in one second. In traditional cinema 24 images per second are used, in video 25 or 30 are used depending on the different systems used in each country. In the age of digital video, the speed can even be doubled to 50 and 60 images per second. We see this indicated in the following way “25fps” (they are 25 photos per second)
I know that the explanation is very basic since each section can be a chapter of a book dedicated to this topic, but as a starting point, which is the objective, it can serve. Just indicate that these recommendations are based on the standards of the audiovisual world, in cinema both the resolution, stink and frame rate go to the director’s taste and are usually much larger than fullHD, so very powerful computers are required and with dedicated graphics to edit these projects.
It is necessary to know in what resolution we have recorded the video and at what frame rate.
For example, if in our camera we have recorded a video at 1080p 30fps we know that we can work with this resolution and we must configure our project with these parameters to have a workspace that adapts to the video with which we are going to work.
If we want to save resources since the video will be broadcast on normal screens we can use a setting of 720.
A simple way to know what format our video has in Linux, Ubuntu and derivatives is to open the video properties with the right button of the mouse and in the Sound / Video tab it gives us all the information.
In the era of HD, videos can consume a lot of space and resources on our computer. From this we could define a recipe to know what size, resolution, we should give to our video.
- Full HD known as 1080 is a high quality video that will consume a lot of resources and space; I would only use it for videos that need to be played on a very large screen. (Its “y” value is 1080 and the “x” is 1920)
- The HD known as 720 is the one most used today to make videos that look good on any TV or computer, saving space and resources. (Its “y” value is 720 and the “x” 1280)
- A good one frame rate (fps) is 25, but it is best to work with the original of the video.
- We can customize these sizes and make videos at lower resolutions, with a smaller size, if they are to be viewed only on mobile devices. In order not to dwell on this point, there is a lot of information on the net on the subject of video resolutions.
Just indicate that one that is very versatile and usual is the resolution of 480, which would be a video with a y-axis of 480px and an x-axis of 854
A trick to reduce resolutions is the following, a 1080 fullHD video will have an x axis of 1920. If we divide these values by 2.25 it will not give a result of 480 and 853.333 as we do not use decimals, the x axis will do it to 854, when there are decimals We always round to the next integer, for example if we divide the fullHD 1080 by 1.5 it gives us the value of the HD 720, the x axis will be 1920 (which is the x axis of 1080) divided by 1.5 (the same value as before to keep the look) and your result will be 1280
- Just add that we can work a video at a certain resolution and then, when exporting, reduce this. From higher to lower resolution the result is optimal, conversely not.
Notes on the resolution:
It is the most controversial parameter. There are many resolutions with different aspects, but today the easiest thing to do is to work with an aspect ratio of 16/9 and 720.
Unless we have to project it on a giant screen, it is best to opt for this resolution.
This term is sometimes called Dimension of the video and we are given the “xy” values of the video; for example in Ubuntu, when we open the video properties in the Sound / Video tab, we get the video resolution as follows:
Dimensions: 1280 x 720
These are the “xy” dimensions of it, as this video preset would be 720. Remember that in the presets or video definitions, the height (“y” axis) is used to define it.
Remember that with a large resolution we can make it small without loss of quality. From small to large, it is lost and can even be pixelated.
And to finish
- If you have any questions about it, you can expose it in the comments (I will be happy to solve it).
- In the following posts we will talk about the different free editors that we can use in Gnu / Linux and which one will be the most appropriate depending on the complexity of the assembly that we want to carry out.