Extron electronics SMP 351 User Manual page 96

3. Select a frame rate (in Hz) from the Resolution drop-down list.
4. Enter a number (from 1 to 30) into the GOP Length field or use the Up and Down
arrows to change the value for the field to set a "group of pictures" (GOP) length. The
default value is 30.
A GOP is a group of successive pictures (frames) within a coded video stream. The
video frames appear in a defined order. Some (known as I frames) contain a full set of
data, others (P frames and B frames) contain a sampled subset of data. GOPs make
it possible to compress the video stream by defining the relationship between and
among frames and then removing duplicated information from each group. The smaller
the GOP length, the more editable the video is, but a higher the bit rate is needed to
transmit the video.
5.
Set the video bit rate (in kbps) by entering a number (from 200 to 10000) into the
Video Bitrate field or use the Up and Down arrows to change the value for that field.
6. Select the type of bit rate control from the Rate Control drop-down list. Options are:
VBR (variable bitrate) — Produces a better quality-to-space ratio compared to a
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CBR file of the same data because it includes more bits for complex segments of
the AV stream and fewer bits for simpler segments. However, it is difficult to predict
the size of the resulting file.
CBR (constant bitrate) — Creates a file of predictable size and stream rate, but of
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variable quality depending on the complexity and motion content of the video.
VCBR (constrained variable bit rate) — Limits the maximum bit rate and sometimes
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the buffer size to create a stream of the best possible quality within a specified
(constrained) bit rate compression limit similar to VBR.
7. Select an encoding compression level from the H.264 Encoding Profile
drop-down list.
High — Offers a higher level of compression and better quality for the selected bit
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rate but is more processor intensive to decode.
Baseline — Offer the lowest compression level and is less processor intensive to
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decode.
Main — Offers mid-range compression and performance.
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8. Select an encoding profile level from the Profile Level drop-down list. This sets the
upper limits of resolution, bit rate,and frame size, and can be used by some devices to
determine whether or not they are able to decode the stream. Settings are from 3.0 (for
lower limits) to 4.1 (for higher limits).
SMP 351 • Web-Based User Interface 90