4.5

184Compressor User Guide
display aspect ratio The ratio between an image’s width and height. For example,
standard-definition (SD) video typically has an aspect ratio of 4:3. High-definition (HD)
video typically has an aspect ratio of 16:9. If SD video is played on an HD display, the
image is either stretched, or is appended with black borders on left and right sides
(pillarboxing). If HD video is played on an SD display, the image will be squeezed or
black borders will appear at the top and bottom (letterboxing).
distributed processing A method of transcoding that accelerates processing of
Compressor batches by distributing the work among multiple computer processors. A
system can distribute parts of a batch to multiple instances of the Compressor application
on a single computer, or to two or more networked computers (each running one or more
instances of Compressor).
droplet A lightweight, standalone app created by Compressor to apply specific settings or
destinations to media files. You can drag and drop media files onto the droplet icon in the
Finder to begin transcoding.
Dolby Digital See AC-3.
Dolby Digital Enhanced See E-AC-3.
E-AC-3 A Dolby Digital compressed audio format often used for encoding surround sound.
E-AC-3 supports up to fifteen channels of audio.
encoder See codec.
file format The output format used to transcode your source media file. Also called a
transcoding format.
FLAC (Free Lossless Audio Codec) A lossless audio format that supports up to 8 channels
of audio and up to 32 bit sample depth.
H.264 A video compression standard in widespread use for recording, distribution, and
Internet streaming of high-definition (HD) video. Also known as MPEG-4 Part 10 or AVC
(Advanced Video Coding).
HDR (high dynamic range) Video stored in a format that processes higher levels of
luminance (brightness) per color component to provide significant improvements in
contrast, detail, and light levels over standard-dynamic-range (SDR) video. HDR can
represent luminances as high as 10,000 nits (candelas per square meter) with a dynamic
range of 14 stops or more, creating more realistic color transitions and revealing more
detail in both shadows and highlights. HDR video is typically combined with wide-gamut
color spaces such as Rec. 2020 or P3 D65 to deliver video any of several formats,
including HDR10, Dolby Vision, and HLG (hybrid log-gamma).
HEVC High-Efficiency Video Coding (also known as H.265), a recently established
compression standard designed to reduce file size while retaining a high-quality image.
HEVC also supports larger frame sizes (including 8K) and HDR10 metadata for high-
dynamic-range video. The Apple Devices transcode setting in Compressor includes two
built-in options for HEVC output. You can also customize the MPEG-4 and QuickTime
Movie settings to use the HEVC encoder. HEVC encoding in Compressor requires macOS
10.13 or later. HEVC playback requires a recent-generation Apple device running macOS
10.13 or later, iOS 11 or later, iPadOS 13 or later, or tvOS 11 or later.