Glossary

360° video

Footage captured by special cameras that point lenses in all directions to create a panoramic sphere of video. A viewer can watch 360° video in any of several ways:

• Through a virtual-reality (VR) headset: This hardware device displays video on a face-mounted screen that’s updated dynamically to show different parts of a scene as the viewer turns their head. Some VR headsets can also display stereoscopic (3D) 360° video, enhancing the immersive experience.

• In a rectangular window: This viewing method is used on a smart phone, tablet, or computer. The viewer scrolls the window to see different parts of the scene.

• On a standard display: This viewing method, with the audience unable to control viewing angles, is similar to watching conventional video, with the added benefit of giving the filmmaker more options for angle choices during editing.

AAC (Advanced Audio Coding)

Also called MPEG-4 Audio. A standard way of compressing and encoding digital audio. AAC-encoded files generally sound as good as or better than MP3 files encoded at the same or even a higher bit rate.

AC-3 (Audio Codec 3, Advanced Codec 3, Acoustic Coder 3)

A Dolby Digital compressed audio format often used for encoding surround sound.

AIFF (Audio Interchange File Format)

A cross-platform audio file format developed by Apple. Like WAV files, AIFF files contain “chunks” of information such as the Sound Data Chunk, which contains the actual sample data, and the Common Chunk, which contains sample rate and bit depth information.

ALAC (Apple Lossless Audio Codec)

A lossless audio codec developed by Apple. ALAC supports up to eight channels of audio, with a maximum sample depth of 32 bits and a maximum sample rate of 384 kHz.

alternative audio

Translated dialog tracks, commentary, or audio descriptions (for the visually impaired) included in an iTunes Store package.

Apple ProRes codecs

Codecs that provide an unparalleled combination of multistream, real-time editing performance, impressive image quality, and reduced storage rates. Apple ProRes codecs take full advantage of multicore processing and feature fast, reduced-resolution decoding modes. All Apple ProRes codecs support any frame size (including SD, HD, 2K, and 4K) at full resolution. The data rates vary based on codec type, image content, frame size, and frame rate.

Apple ProRes includes the following formats:

• Apple ProRes 4444 XQ: The highest-quality version of Apple ProRes for 4:4:4:4 image sources (including alpha channels), with a very high data rate to preserve the detail in high-dynamic-range imagery generated by today’s highest-quality digital image sensors. Apple ProRes 4444 XQ preserves dynamic ranges several times greater than the dynamic range of Rec 709 imagery—even against the rigors of extreme visual effects processing, in which tone-scale blacks or highlights are stretched significantly. Like standard Apple ProRes 4444, this codec supports up to 12 bits per image channel and up to 16 bits for the alpha channel. Apple ProRes 4444 XQ features a target data rate of approximately 500 Mbps for 4:4:4 sources at 1920 x 1080 and 29.97 fps.

• Apple ProRes 4444: An extremely high-quality version of Apple ProRes for 4:4:4:4 image sources (including alpha channels). This codec features full-resolution, mastering-quality 4:4:4:4 RGBA color and visual fidelity that is perceptually indistinguishable from the original material. Apple ProRes 4444 is a high-quality solution for storing and exchanging motion graphics and composites, with excellent multigeneration performance and a mathematically lossless alpha channel up to 16 bits. This codec features a remarkably low data rate compared to uncompressed 4:4:4 HD, with a target data rate of approximately 330 Mbps for 4:4:4 sources at 1920 x 1080 and 29.97 fps. It also offers direct encoding of, and decoding to, both RGB and Y’C_BC_R pixel formats.

• Apple ProRes 422 HQ: A higher-data-rate version of Apple ProRes 422 that preserves visual quality at the same high level as Apple ProRes 4444, but for 4:2:2 image sources. Apple ProRes 422 HQ offers visually lossless preservation of the highest-quality professional HD video that a single-link HD-SDI signal can carry. This codec supports full-width, 4:2:2 video sources at 10-bit pixel depths, while remaining visually lossless through many generations of decoding and reencoding. The target data rate of Apple ProRes 422 HQ is approximately 220 Mbps at 1920 x 1080 and 29.97 fps.

• Apple ProRes 422: A high-quality compressed codec offering nearly all the benefits of Apple ProRes 422 HQ, but at 66 percent of the data rate for even better multistream, real-time editing performance. The target data rate of Apple ProRes 422 is approximately 147 Mbps at 1920 x 1080 and 29.97 fps.

• Apple ProRes 422 LT: A more highly compressed codec than Apple ProRes 422, with roughly 70 percent of the data rate and 30 percent smaller file sizes. This codec is perfect for environments where storage capacity and data rate are at a premium. The target data rate of Apple ProRes 422 LT is approximately 102 Mbps at 1920 x 1080 and 29.97 fps.

• Apple ProRes 422 Proxy: An even more highly compressed codec than Apple ProRes 422 LT, intended for use in offline workflows that require low data rates but full-resolution video. The target data rate of Apple ProRes 422 Proxy is approximately 45 Mbps at 1920 x 1080 and 29.97 fps.

Note: Apple ProRes 4444 and Apple ProRes 4444 XQ are ideal for the exchange of motion graphics media because they are virtually lossless, and are the only Apple ProRes codecs that support alpha channels.

AVCHD

A high-definition (HD) video format that uses Advanced Video Coding (AVC) compression (also known as MPEG-4 part 10 or H.264). Many Blu-ray players can play red laser discs with AVCHD format content.

baseline

In stereoscopic footage, the horizontal distance between the two camera lenses used to capture the images (also known as the interaxial distance).

batch

In Compressor, one or more jobs to be processed. All jobs contained within the batch (shown in the batch area of the Compressor window) are submitted collectively when you begin the transcoding process.

bit rate

The number of bits per second in the transmission of a digital video or audio signal. The higher you set the bit rate, the better the quality of the output file. However, higher bit rates require larger file sizes.

CAF (Core Audio Format)

A flexible file format for storing and manipulating digital audio data. CAF provides high performance and flexibility, and is scalable to future ultra high-resolution audio recording, editing, and playback.

captions

Onscreen text superimposed over a video and synchronized to the video and audio. Compressor supports three industry-standard caption formats: CEA-608 closed captions, iTT (iTunes Timed Text) subtitles, and SRT (SubRip Text) subtitles.

CEA-608 closed captions

An industry-standard format for delivering onscreen text synchronized to a video. Originally developed for people who are deaf or hard of hearing, CEA-608 closed captions (also known as Line 21 text) are frequently used on televisions in loud environments (such as bars and airports). CEA-608 closed captions, which use the .scc filename extension, offer numerous formatting options. Viewers can turn closed captions on or off while watching television shows, movies, web videos, and other programs. In Compressor, CEA-608 closed captions are compatible with iTunes Store packages and many transcode presets.

codec

Short for compressor/decompressor, or encode/decode. A software component used to translate video or audio from its current form to a different, digitally compressed form. A codec encodes a data stream or signal for transmission, storage or encryption, or decodes it for playback or editing. A similar term, encoder, is used to describe hardware that performs the same activity.

color depth

The number of bits used to represent color in each color channel—red, green, and blue.

color space

The range of colors available for an image, sometimes called gamut. A wider gamut allows for more possible color values and permits more accurate representation of color.

Composition playlist (CPL)

An XML file that defines the playback order for the media assets of an Interoperable Master Format (IMF) package. It also contains metadata associated with the playback order. The CPL allows IMF packages to combine multiple assets into a single playback of a program.

cubic projection

A spatial projection mode that represents spherical data as an unfolded cube with six faces.

delivery partner

A content aggregator or encoding house certified by the iTunes Store and authorized to submit iTunes Store packages to the store for sale. These partners ensure your content is properly configured and formatted to meet the stringent submission requirements of the iTunes Store. They can also provide billing and support services after your video becomes available for sale.

descriptive audio

An alternative audio track that includes voice narration to help visually impaired consumers understand what’s happening onscreen. Descriptive audio narration is usually delivered during the natural pauses in dialog or between critical sound elements. An iTunes Store package can contain multiple descriptive audio tracks (in multiple languages, for example).

destination

In Compressor, a group of one or more transcode presets plus a post-transcoding action. If you use a destination to transcode a file, one or more new files are created to the preset’s specifications and then an action is automatically performed on the transcoded file. For example, the Add to TV Home Videos destination creates a file optimized for viewing on Apple TV. After the file is processed, the Add to TV Home Videos action automatically copies the output file to your Home Videos library on Apple TV.

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).

dithering

A deliberately applied form of noise that simulates additional colors in a limited palette by blending color transitions. For example, a pattern of yellow and blue can be applied to give the impression that green appears in the image.

Dolby Digital

See AC-3.

Dolby Digital Enhanced

See E-AC-3.

Dolby Vision 8.4

A high-dynamic-range video format developed by Dolby Laboratories and optimized for Apple devices.

downmix

The process of outputting fewer audio channels than are contained in the source file. For example, you can use a source file containing surround sound (5.1 channel layout) to output a file containing a stereo file with a left and right channel or a mono file with a single channel.

drop frame timecode

A timecode format that prioritizes representing time elapsed instead of frames elapsed when a clip is not 30 fps. Drop frame timecode typically displays a semicolon between seconds and frames.

droplet

A lightweight, standalone app created by Compressor to apply specific presets or destinations to media files. You can drag and drop media files onto the droplet icon in the macOS Finder to begin processing.

dynamic range

The difference, in decibels, between the loudest and softest parts of a recording.

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.

equirectangular projection

A spatial projection mode that squeezes and distorts the spherical data like a flat map of the spherical earth.

field of view

In stereoscopic footage, the horizontal field of view of the lenses used to capture the images.

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.

frame-packed

A term used to describe stereoscopic video formats that "pack” both eye views into the same frame. Common frame-packed formats are Over/Under, in which one eye view (typically the left eye) is placed on top of the other eye, and Side by Side, in which both eye views are placed next to each other.

group of pictures (GOP)

A file compression method that groups frames, or “pictures,” in encoded video to remove redundant frames. There are three GOP frame types: I-frames (intra-coded frames), P-frames (predictive frames), and B-frames (bidirectional predictive frames). These are collectively called a group of pictures (GOP). MPEG-2 and H.264 encoding in Compressor combine frames into groups of pictures during the encoding process to output a highly compressed file.

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).

hero eye

The default eye view in a stereoscopic pair of video files. An MV-HEVC file contains two layers: the base layer encodes the hero-eye view, and a second layer encodes only the portions of the other eye view that differ from the hero eye. This improves playback and encoding efficiency. The hero eye is typically designated with a tag assigned by the cameras during video capture, but you can reassign the hero eye in Compressor prior to encoding. When stereoscopic footage is used in a 2D project, the hero eye’s layer and metadata is used.

HEVC

High-Efficiency Video Coding (also known as H.265), a video 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 preset in Compressor includes three built-in options for HEVC output. You can also customize the MPEG-4 and QuickTime Movie presets to use the HEVC encoder. HEVC encoding in Compressor requires macOS 10.13 or later. HEVC playback requires an Apple device with macOS 10.13, iOS 11, iPadOS 13, tvOS 11, or later.

HLG (hybrid log-gamma)

A mathematical HDR transfer function that converts image signal values in a video file to scene-relative light levels. HLG, which was developed by the BBC and the NHK (Japan Broadcasting Corporation), requires no metadata and is also compatible with SDR displays. In Compressor, HLG is used with the Rec. 2020 color space to create video files in the hybrid log-gamma HDR standard.

horizontal disparity

In stereoscopic footage, the amount of horizontal shift in left- and right-eye images to set the perceived depth of a 3D scene (also called convergence). When horizontal disparity is negative, content in the footage appears closer; when it’s positive, content seems farther away.

HTTP Live Streaming

An HTTP-based media streaming communications protocol, commonly used to send audio and video over HTTP from an ordinary web server for playback on a variety of computers and devices. HTTP Live Streaming supports multiple alternate streams at different bit rates, allowing the client software to switch streams intelligently as network bandwidth changes.

i-frame (intra-coded picture)

One type of frame used to define the GOP (Group of Pictures) pattern used during MPEG-2 or H.264 encoding. A GOP pattern can also include P-frames (predictive coded picture) and B-frames (bipredicitive coded picture).

inspector pane

An area on the right side of the window when Compressor is in Current view. When you select a preset, l