Tektronix MTM400 - Manual (Page 147)

Triggered Recording
3-102 MTM400 MPEG Transport Stream Monitor User Manual
Desired Recording Packets
Two fields which indicate the number of packets (at
204 bytes/packets) that are to be recorded in the reserved
memory (Total Memory Size) and the amount of memory that
will be used.
Enter the number of packets required and select Set to confirm
the setting.
NOTE. Any value can be entered in the Desired Record Packets field. The required
memory will be calculated and displayed, even if it exceeds the available memory.
However, when recording actually starts, the entered value is automatically
adjusted to reflect the available memory.
Total Memory Size
Displays the total available system memory.
Pre-Trigger Recordings
A percentage of a stream can be recorded before a trigger event as specified by the
Pre-Trigger setting. The start of recording is dependent upon the selected trigger
type. However, the stream is being recorded in memory at all times; the available
memory is used as a circular buffer, in that it is filled and written over
continuously until a trigger event occurs.
NOTE. A Circular Buffer is an area of memory used to store a continuous stream of
data by starting again at the beginning of the buffer after reaching the end.
As soon as the trigger event occurs, recording will commence. Recording
continues until the memory buffer is full. The recording will remain in memory
until it is manually cleared, typically after it is uploaded to a client PC.
The Pre-trigger set up can be changed only when no recording activity is in
progress.
The Pre-trigger setting allows the proportion of data saved before a trigger event to
be specified as a percentage of the final recorded file. Editing the value or dragging
the slider in the tab can change the proportions.