the internal color space of CINELERRA-GG is X11 sRGB
without color profile. CINELERRA-GG 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
the color model video that is selected in the dropdown. Color model
is important for video playback because video has the disadvantage
of being slow compared to audio. Video is stored on disk in one
colormodel, usually a YUV derivative. When played back, CINELERRA-GG
decompresses it from the file format directly into the format of the
output device. If effects are processed, the program decompresses
the video into an intermediate colormodel first and then converts it
to the format of the output device. The selection of an
intermediate colormodel determines how fast and accurate the effects
are. A list of the current colormodel choices follows.
- RGB-8 bit
- Allocates 8 bits for the R, G, and B channels
and no alpha. This is normally used for uncompressed media with low
- RGBA-8 bit
- Allocates an alpha channel to the 8 bit RGB
colormodel. It can be used for overlaying multiple tracks.
- Allocates a 32 bit float for the R, G, and B
channels and no alpha. This is used for high dynamic range
processing with no transparency.
- This adds a 32 bit float for alpha to
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
- 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
derivative allows video to be processed fast with the least color
- YUVA-8 bit
- Allocates an alpha channel to the 8 bit YUV
colormodel for transparency.
In order to do effects which involve alpha
channels , a colormodel with an alpha channel must be selected.
These are RGBA-8 bit, YUVA-8 bit, and RGBA-Float. The 4 channel
colormodels are slower than 3 channel colormodels, with the slowest
being RGBA-Float. Some effects, like fade, work around the need for
alpha channels while other effects, like chromakey, require an alpha
channel in order to be functional. So in order to get faster
results, it is always a good idea to try the effect without alpha
channels to see if it works before settling on an alpha channel and
slowing it down.
When using compressed footage, YUV colormodels are usually faster
than RGB colormodels . 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
processed in YUV. Years of working with high dynamic range footage
has shown floating point RGB to be the best format for high dynamic
range. 16 bit integers were used in the past and were too lossy and
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. See also 17.3, 17.4 and A.3.