4.5

187Compressor User Guide
PQ (perceptual quantizer) A mathematical transfer function that converts image signal
values in a video file to absolute light levels on an HDR-capable display. Designed to
approximate the sensitivity of human eyes, PQ allows for better levels of contrast at all
light levels. In Compressor, PQ is used with the Rec. 2020 and P3 D65 wide-gamut color
spaces to create video files in the industry-standard HDR formats, HDR10 and Dolby Vision.
preview area In Compressor, the area where you can play your source file and preview
your output file. After you apply effects or change the properties of the setting that will
transcode your source file, you can compare the “before” and “after” versions by clicking
the Comparison button (under the timeline). The screen is divided by a vertical white line,
with the source file shown on the left and the preview of the transcoded file shown on
the right.
QuickTime The cross-platform multimedia technology that allows macOS and Windows
applications to capture and play back video, audio, and still-image files.
Rec. 709 The standard-gamut 8-bit color space used by high-definition TV displays, the
Blu-ray Disc format, and most TV broadcasters. Also known as ITU-R Recommendation
BT.709.
Rec. 2020 A wide-gamut color space developed for future consumer display devices but
useful today for mastering (to future-proof your projects) and for 4K and 8K TV projects.
Even though no currently available consumer TVs or computer monitors can display the
entire Rec. 2020 palette, wide-color-gamut displays can show a subset of those colors.
Also known as ITU-R Recommendation BT.2020.
resolution Image resolution refers to the frame size of the video. Image resolution is
expressed in terms of the width and height (the frame size) of the image in pixels. Higher-
resolution images contain more detail but also create larger files that take longer to
download. Your electronic devices (computer, iPhone, iPad, iPod, and so on) also have
screen resolution. Resolution is expressed in terms of the width and height of the image
in pixels (for example, 640 x 360 pixels).
When you add a setting to a source media file, Compressor determines appropriate
resolution sizes you can use, based on the image sizes used in the movie and on the
setting that you’re using to output the file.
sample rate The number of times per second that music waveforms (samples) are
captured digitally. The higher the sample rate, the higher the quality and the larger the
file size.
sample size The number of bits in each audio sample; determines the potential dynamic
range of the sound.
SDR (standard dynamic range) The conventional technique for processing luminance
(levels of brightness) and color values in images, developed in the mid-1900s, with an
upper luminance limit of 100 nits (candelas per square meter) and a dynamic range of
6–10 stops.
setting In Compressor, a group of preconfigured properties that you can apply to a source
media file. Settings are used to transcode files into commonly used audio and video
formats for Apple devices, podcasting, Internet streaming, post-production, and so on.
Each setting includes adjustable properties like output file format, retiming instructions,
and optional effects.