channels to see if it works before settling on an alpha channel and
slowing it down.
- When using compressed footage, YUV colormodels \index{YUV} are usually faster
+ When using compressed footage, YUV colormodels \index{yuv} are usually faster
than RGB colormodels \index{RGB}. They also destroy fewer colors than RGB
colormodels. If footage stored as JPEG or MPEG is processed many
times in RGB, the colors will fade whereas they will not fade if
each output frame are interpolated.
\end{description}
+\section{Best practice in pre-editing}%
+\label{sec:best_practice_pre_editing}
+
+\CGG{} supports the simultaneous presence in the Timeline of sources with different frame sizes and frame rates. However, audio/video synchronization problems may occur due to their different timing.\protect\footnote{credit to sge and Andrew Randrianasulu}
+Plugins that rely on the timing of each frame, for example \textit{Motion} and \textit{Interpolate} plugins, may have problems when used at the same time with engines which increase frame rate. Frame rate per definition cannot be increased without either duplicating some frames or generating them in some intelligent way. But to work reliably, the \textit{Motion} plugin requires access to all actual frames. These kinds of plugins (and also the rare cases of audio/video desync) explicitly require the \textit{Play every frame} option.
+
+There is no problem as long as the source fps, project fps, and destination fps are identical. In most cases, high frame rates such as 120 or 144 or any fps, will be just fine for \textit{Motion} provided that source footage all has the same frame rate.
+
+But when \textit{project} and \textit{source} frame rates are different (or \textit{project} and
+\textit{rendered} fps), then the \CGG{} engine has to either duplicate (interpolate) some frames or throw some away. Because of this, the audio tracks and the timeline get out of sync with such accelerated (or slowed down) video. And to make \textit{Motion} plugins reliably calculate interframe changes, you have to ensure the consistent frame numbers and frame properties.
+
+Generally, best practice is to perform the following sequence of preparations for video 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.
+ \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.
+ \item Whole editing: if you need to change frame rate of some restricted part, particularly when smooth acceleration/deceleration is needed, it can be done here. 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}
+
+\CGG{} does not have color management \index{color management}, but we can still give some general advice on how to set color spaces:
+
+\begin{enumerate}
+ \item Profiling and setting the monitor: \\
+ source: \textit{sRGB} $\rightarrow$ monitor: \textit{sRGB} (we get a correct color reproduction) \\
+ source: \textit{sRGB} $\rightarrow$ monitor: \textit{rec709} (we get slightly dark colors) \\
+ source: \textit{sRGB} $\rightarrow$ monitor: \textit{DCI-P3} (we get over-saturated colors) \\
+
+ source: \textit{rec709} $\rightarrow$ monitor: \textit{rec709} (we get a correct color reproduction) \\
+ source: \textit{rec709} $\rightarrow$ monitor: \textit{sRGB} (we get slightly faded colors) \\
+ source: \textit{rec709} $\rightarrow$ monitor: \textit{DCI-P3} (we get over-saturated colors)
+ \item It would be better to set the project as RGB(A)-FLOAT, allowing system performance, because it collects all available data and does not make rounding errors. If we can't afford it, starting from YUV type media it is better to set the project as YUV(A)8, so as not to have a darker rendering in the timeline. On the contrary, if we start from RGB signals, it is better to use RGB(A)8. If we don't display correctly on the timeline, we'll make adjustments from the wrong base (metamerism) and get false results.
+ \item Among the rendering options always set the values \\
+ \texttt{colorspace=...} (color model); \\
+ \texttt{color\_trc=...} (gamma correction) \\
+ \texttt{color\_primaries=...} (gamut).
+
+ These are only metadata that do not affect rendering but when the file is read by a player later they are used to reproduce the colors without errors.
+\end{enumerate}
+
+
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