[Cin] OT: comments from youtube can be saved, too

[Andrea paz]

@Phyllis
I edited the manual again so do not consider the previous attachment
valid, only this second one.
@All
In addition to eliminating my error (canvas = timeline) I made some
other small additions based on Igor Vladimirskji's articles (he gave
me permission). Can you check if they seem useful or are they to be
corrected?

In addition to Latex I also attach a text file for those who want to
see and correct the changes right away, without waiting for the new
version of the manual to be published.
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3.2 Video attributes

 \item[Canvas size:] \index{canvas size} sets the size of the video output \index{output size}. In addition,
each track also has its own frame size.  Initially, the New Project dialog creates video tracks whose size match the video output.  The video track sizes can be changed later without changing the video output. We have: Project size = W x H pixels = canvas size = output size



\item[Aspect ratio:] \index{aspect ratio} sets the aspect ratio; this aspect ratio refers to the screen aspect ratio.  The aspect ratio is applied to the video output (canvas). It can be convenient to vary the size of the canvas in percentage terms, instead of having to calculate the number of W x H pixels. The aspect ratio can be different than the ratio that results from the formula: $\dfrac{h}{v}$ (the number of horizontal pixels divided into the number of vertical pixels).  If the aspect ratio differs from the results of the formula above, your output will be in non-square pixels.


3.3 Best practice in pre-editing

\begin{enumerate}
	\item Motion stabilization, and maybe some other preparations, to improve the quality of the source video is best done under the properties identical to the properties of the original video; it may be different codec, but same frame size and same frame rate. For stabilization you can use ffmpeg command line plugins called \textit{vidstabdetect} and \textit{vidstabtransform}.
	\item To have a workflow at the highest quality it may be convenient to convert the sources into image sequences (e.g. OpenEXR). Especially if we want to exchange files with other Color or Compositimg programs that preferably use image sequences.
	\item Unify the color models. It is convenient to unify the color models of the sources because they would give different and inconsistent results with each other once displayed in the Compositor window.
	\item If we intend to do some color correction or compositing with VFX, it is convenient to do some de-noising on the sources to make their pixels more homogeneous and suitable for post processing. De-noising is a heavy operation for the system so it may be convenient to do it in pre-editing.
	\item If you need to alter the frame rate, for example because different source clips have different frame rates, then recode all the necessary clips to the same future project frame rate. Here frame sizes can still have different sizes, but frame rates should be all the same.	If you need to change frame rate of some restricted part, particularly when smooth acceleration/deceleration is needed, it can be done in timeline. But if frame rate has to be changed only due to different source fps, it is better to do it during the preparation stage.
\end{enumerate}


2.2.4 The Temporary

\subsubsection*{The Temporary}%
\label{ssub:output_size}
\index{temporary}

\CGG{}'s compositing routines use a \textit{temporary} which is a single frame of video in memory where graphics processing takes place. By default the size of the temporary is that of the project (W x H), i.e., the output size. But if the tracks on the timeline have various sizes different from those of the project, then the temporary will take the size of the active track (viewport = green border). We can also change the size of the viewport using the Camera tool, as well as pans and zooms the temporary displayed in it. Effects are processed in the temporary and as such are affected by the temporary size.  In the case of the camera, its viewport is the temporary size.  The size of the temporary and of the output in the compositing pipeline can be different and vary for any particular frame. However, projectors are rendered to the output and so are affected by the output size. The temporary is the basis on which the Projector tool acts to display the canvas on the Compositor window. The canvas always has the size of the project, although with the projector we can make pans and resizes of the red border inside it. When the temporary is smaller than the output, the temporary will have blank borders around the region in the output.  When the temporary is larger than the output, it will be cropped.



2.2.4 Track and Output size (at the end section)

To clarify, let's take an example.

If we load a media (M) into Resources and adjust the size of the project to the size of M, we will get the canvas size of the media (Wm x Hm). We can see in the Set Format window that the project's default values (W x H) have changed to those of M (Wm x Hm). The tracks on the timeline can have different sizes, but what we will see on the canvas, that is, in the Compositor window, is always the output size i.e. the size of the project. Tracks with smaller sizes will be seen with black bands; tracks with larger sizes will be cropped. Each track has its own size but we will see it inserted in the output size. If we change the output size the tracks will not change, remaining in their original size. We can only change the size of the tracks by manually acting on each one in the ways seen before. Finally, if we create a new track in a project of size W x H, it will assume the size of the project automatically.
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