Glossary of Useful Terms

Bit Depth: The number of data bits used for each individual sample. The amount of bits determines the number of discrete levels within which it is possible to place a sample. 8-10 bit is common for video and 16-24 bit is common for audio.

Bit Rate:  The amount of sample data in a digital signal that is collected or streamed per unit of time. Usually expressed as ‘bits per second’ (bps) or ‘Megabits per second’ (Mbps), a dynamic media file’s bit rate is the product of multiplying the sample rate by the bit depth of the samples

Checksum:  A relatively small code that is derived from a much larger code by a checksum algorithm for the purpose of verifying that the larger code (usually the data which constitutes a file) remains unchanged during transfer or long-term storage. Any change or corruption of the file can be discerned by comparing the checksum produced prior to a file’s transfer or storage with a second checksum produced later by the same algorithm; if the second checksum does not match the first, then it can be surmised that the file has changed during the intermediate time.

Chroma Subsampling: see Wikipedia description.  

Color Bars (SMPTE): see Wikipedia description. 

Digital Preservation: Duplication of a deteriorating piece of media by digital means, which entails using a digitization device to sample the visual and audio components of the media and a computer to record the data into files. This is done for the purpose of creating a more stable digital copy of the original source. The term might also be used to refer to the policies, strategies, and actions such as reformatting and migrating of digital files or content to ensure access over time.

Field Order: Interlaced field that is displayed first. Often referred to as either top or bottom field first.

File Size: Amount of data in a file. Usually measured in bytes, K (kilobytes) MB megabytes, or GB (gigabytes).

Generation (film): Refers to the order of duplication of film elements. A copy of a copy of an original negative is said to be a “third generation” element. Multiple film elements can be part of the same generation, e.g. if the same camera negative is used to produce two second-generation intermediate positives.

Metadata: The National Information Standards Organization (NISO) defines Metadata as “…structured information that describes, explains, locates, or otherwise makes it easier to retrieve, use, or manage an information resource. Metadata is often called data about data or information about information.”

OpenDML AVI File Format Extension: File standard that allows for AVI files larger than 2 GB.

Preservation: Actions taken to reproduce moving image and sound recordings to create a new preservation copy that remains as close to the original intent as possible. This may be a new analog copy or a digital copy that captures the inherent qualities of the source object. This definition may be different for other specialties.

Reformatting: A process in which a copy or derivative is created from the original media. This may be done for preservation or access purposes.

Restoration: The actions taken to produce a version of a piece of media that is as close to the ideal original as possible. In the context of film for example, these actions may include repair, dirt removal, scratch removal, stabilization, color correction, reconstruction of lost content, and reformatting. The related terms “preservation” and “conservation” concern the actions taken to assure that a piece of media will continue to exist in its current form, whereas restoration implies intervention to alter the media to a different state, ideally one which is faithful to its original form. Restoration can simply be understood as an effort to reverse degradation.

Sampling Rate: The frequency at which information from the original recording is sampled or collected from a continuous signal. The rate is given in hertz (Hz) which equals cycles per second. One common example is the audio CD which has a sampling rate of 44,100 Hz, or 44.1 kHz.

Video Format: The format of a video such as PAL, NTSC, or HD.

Video and Audio Properties from Tektronix Glossary of Video Terms and Acronyms:

  • Audio Clipping: When recording audio, if an input signal is louder than can be properly reproduced by the hardware, the sound level will be cut off at its maximum
  • Brightness: The value of a pixel along the black-white axis.
  • Contrast: The difference between the white and black picture levels.
  • Frame Rate: The rate at which frames of video data are scanned on the screen. In an NTSC system, the frame rate is 29.97 frames per second (Fps). This changed from 30 Fps so that the color subcarrier could be interleaved between both the horizontal line frequency and sound carrier. For digital scans of motion picture film originals, the frame rate is typically 24fps.
  • Resolution (Video): The basic measurement of how much information is on the screen (or amount of detail in an image). A typical NTSC resolution is 720 x 486, which refers to the number of distinct pixels in the horizontal axis by the number of horizontal lines.
  • Video Signal Levels: The chroma and luma levels in a video. Chrominance (also referred to as chroma) is the depth or saturation of color and luminance (also referred to as luma) is the brightness signal.

Additional Resources

Federal Agencies Digitization Guidelines Initiative (FADGI) Glossary

A/V Artifact Atlas