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188Compressor User Guide
source media file In Compressor, the original media file to be converted to a new file
format. One source file is required for each job.
SRT (SubRip Text subtitles) An industry-standard format for delivering onscreen text
synchronized to the audio or video of a video program. SRT subtitles can be used to deliver
foreign-language translations or a transcript of dialog, narration, or audio descriptions
to people who are deaf or hard of hearing. SRT subtitles, which use the .srt filename
extension, offer more limited formatting options than CEA-608 captions. In Compressor,
you can specify whether to let viewers turn SRT subtitles on or off (for example, for full
foreign-language translations) or force subtitles to appear onscreen (for example, for
specific characters in a movie who speak a different language). In Compressor, many built-
in settings and destinations support SRT subtitles, including Apple Devices (in both the
H.264 and HEVC codecs), ProRes, Create DVD, and other settings that use the QuickTime
Movie, MPEG-2, and MPEG-4 formats.
storage aspect ratio (SAR) The ratio between an image’s width and height when it is
stored. Storage aspect ratio can differ from display aspect ratio (DAR) resulting in a file
that must be stretched or squeezed during playback to appear correct. This disparity can
allow a camera format limited to 4:3 recording to successfully record a widescreen image
by “squeezing” the image during recording. If the image is unsqueezed during playback it
will display correctly in its widescreen aspect ratio. This is called an anamorphic image.
transcoding The process of converting files from their original format to a different format.
Closely related terms include compression, which specifically refers to data reduction, and
encoding, a term that is essentially synonymous with transcoding, but doesn’t emphasize
the conversion aspect.
uncompressed 8-bit and 10-bit 4:2:2 Video formats used to store 8-bit or 10-bit 4:2:2
Y’C
B
C
R
video without employing data compression. Bypassing compression reduces the
computer’s processing load but increases the data rate considerably. A large-capacity
RAID storage system is typically required to work effectively with uncompressed video.
In many cases, Apple ProRes is a better choice.
The data rate of uncompressed 4:2:2 video varies according to frame size and frame rate.
For example, at a frame size of 1920 x 1080 and a frame rate of 29.97 fps, the data rate is
1.0 Gbps for uncompressed 8-bit 4:2:2 video and 1.3 Gbps for uncompressed 10-bit 4:2:2
video.
WAVE (or WAV) An audio file format most commonly used for storing uncompressed linear
pulse code modulation (LPCM) audio data.
wide color gamut A video color space capable of reproducing a broader palette of colors
than traditional standard-gamut color spaces. Recent display devices—including 4K
televisions and computer monitors, newer Mac, iOS, and iPadOS devices, and Apple TV
4K (when connected to a wide-gamut television)—can render more vivid and lifelike hues
(in addition to all the hues that standard-gamut devices can display). Accordingly, the
video industry has adopted a wide-gamut color standard called Rec. 2020. Although most
currently available wide-gamut devices support only a subset of the colors contained in
the full Rec. 2020 specification, future imaging devices should be able to render more and
more of those hues.