\end{figure}
In addition to the standard settings for sample rate, frame rate,
-and frame size, \CGG{} uses some less traditional settings like
+and frame size (canvas size), \CGG{} uses some less traditional settings like
channel positions, color model, and aspect ratio. The aspect ratio
-refers to the screen aspect ratio (SAR).
+refers to the display aspect ratio (DAR).
Edit decision lists , the EDL \index{EDL} stored in XML, save the project
settings. Formats which contain media but no edit decisions just
frame rate that you load. Media is reframed to match the project
framerate.
-\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.
-
-\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. 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.
-
-\item[Auto aspect ratio:] if this option is checked, the Set Format
+\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 matches the video output. The video track sizes can be changed later without changing the video output. We have: Project size = $Width \times Height$, pixels = canvas size = output size .
+
+\item[W/H Ratio] Sets the ratio of the new canvas size (Width, Height) from the old (previous) canvas size (Width, Height).
+
+\qquad W Ratio = $\frac{W_f}{W_i}$ \qquad H Ratio = $\frac{H_f}{H_i}$
+
+with $W_f$/$H_f$: final Width and Height; $W_i$/$H_i$: initial Width and Height.
+
+The new canvas size is recalculated based upon a certain factor in the \texttt{W Ratio}, \texttt{H Ratio} fields. A practical use-case: the current resolution is $640 \times 480$, and for some reason you want Width to be 1.33 times bigger. You don't have to calculate what $640 \times1.33$ is; you type 1.33 into the \texttt{Width} input instead, and \CGG{} calculates it for you. W/H Ratio works as a local calculator. Warning: if you vary W/H Ratio without adjusting Display aspect ratio, we may get non-square pixels resulting in anamorphic frame distortion.
+
+\item[Display aspect ratio:] \index{aspect ratio} sets the aspect ratio; this aspect ratio refers to the display aspect ratio (DAR). 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 Width x Height 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.
+
+\item[Auto aspect ratio:] if this option is checked, the \texttt{Set Format}
dialog always recalculates the Aspect ratio setting based upon the
given Canvas size. This ensures pixels are always square.
-\item[Color model:] \index{color model} the internal color space of \CGG{} is X11 sRGB
+\item[Color model:] \index{color!model} the internal color space of \CGG{} is X11 sRGB
without color profile. \CGG{} always switches to sRGB when applying
filters or using the compositing engine. Different case for
decoding/playback or encoding/output; the project will be stored in
RGB-Float. It is used for high dynamic range processing with
transparency. Or when we don't want to lose data during workflow,
for example in color correction, key extraction and motion
-tracking.
+tracking. Note: even if \CGG{} outputs fp32, exr/tiff values there are normalized to 0-1.0f.
\item[YUV-8 bit] Allocates 8\,bits for Y, U, and V. This is used
for low dynamic range operations in which the media is compressed in
the YUV color space. Most compressed media is in YUV and this
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
slow for the amount of improvement. RGB float does not destroy
information when used with YUV source footage and also supports
brightness above 100\,\%. Be aware that some effects, like
-Histogram, still clip above 100\,\% when in floating point.
+Histogram, still clip above 100\,\% when in floating point. See also \ref{sec:color_space_range_playback}, \ref{sec:conform_the_project} and \ref{sec:overview_color_management}.
\item[Interlace mode:] \index{interlacing} this is mostly obsolete in the modern digital
age, but may be needed for older media such as that from broadcast
lines of interlaced source footage. The alternating lines missing on
each output frame are interpolated.
\end{description}
+A tip on how to eliminate Letterbox/Pillarbox black bands in the Set
+Format window can be found here: \nameref{sub:remove_letterbox}.
+
+\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. 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 Uniform 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}
+
+\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 Having correct color representation in the Compositor can be complicated. You can convert the imput \textit{YUV color range} to a new YUV color range that provides more correct results (i.e. MPEG to JPEG). The \texttt{Colorspace} plugin can be used for this conversion.
+ \item Among the rendering options always set the values \\
+ \texttt{color\_trc=...} (gamma correction) \\
+ \texttt{color\_primaries=...} (gamut) \\
+ \texttt{colorspace=...} (color spaces conversion, more depth-color); \\
+ or \\
+ \texttt{colormatrix=...} (color spaces conversion, faster).
+
+ 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}
+
+For more tips on how \CGG{} processes colors on the timeline see \nameref{sec:color_space_range_playback}, \nameref{sec:conform_the_project} and \nameref{sec:overview_color_management}.
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