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Latency:
The
factor of data access time due to disk rotation. The faster a disk
spins the quicker it will be at the position where the required data can
start to be read. As disk diameters have decreased so rotational speeds
have tended to increase but there is still much variation. Modern
31/2-inch drives typically have spindle speeds of between 3,600 and
7,200 revolutions per minute, so one revolution is completed in 16 or 8
milliseconds (ms) respectively. This is represented in the disk
specification as average latency of 8 or 4 ms. Layered embedded
encoding: The process of compressing data in layers such that successive
layers provide more information and thus higher quality reconstruction
of the original. That is, a single stream of data can supply a range of
compression and thus, in the case of video, a scalable range of video
resolution and picture quality. This is particularly useful for a
muticast where a single stream is sent out and people are connecting
over varying bandwidths. The low bandwidth connection can take just the
lower layers while the high-bandwidth connection can take all of the
layers for the highest quality.
Letterbox:
Image of a widescreen picture on a standard 4:3 aspect ratio television
screen, typically with black bars above and below. Used to maintain the
original aspect ratio of the source material. See also: Side panels and
pillarbox.
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Live-streaming:
Streaming media that is broadcast to many people at a set time. See
also: On-demand streaming.p> Lossless compression: Reducing the
bandwidth required for transmission of a given data rate without loss of
any data.
Lossy
compression: Reducing
the total data rate by discarding data that is not critical. Both the
video and audio for DTV transmission will use lossy compression. See
also: Algorithm.
LSB:
Least significant bit. The bit that has the least value in a binary
number or data byte. In written form, this would be the bit on the
right. For example: Binary 1101 = Decimal 13. In this example the
right-most binary digit, 1, is the least significant bit--here
representing 1. If the LSB in this example were corrupt, the decimal
would not be 13 but 12. See also: MSB.
Luminance:
The
component of a video signal that includes information about
its brightness. See also: Chrominance.
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