User guide

SiraView User Guide
8
In some cases SiraView cannot tell whether a time offset should be applied. You should make a
judgement in such cases as to whether the displayed time is accurate, or whether a correction
should be made.
Anywhere that you see the time info icon in SiraView, you may click on it to obtain further
information about the time displayed.
In the example on the left, you can see that there is no time offset embedded in the video file. This
means that the displayed time and the embedded time are the same.
On the right, you can see that there is an offset of +60 minutes. This means that the time displayed
by SiraView will be 60 minutes ahead of the time stored in the file. In other words, the time stored in
the file was probably recorded in British Summer Time (BST).
Time Display
Some video formats do not store accurate time information for every frame; SiraView must then
make an assumption about the time in order to play back at a sensible speed. For example, if the
recorder only stores times to the nearest second, but records 25 frames per second, then there will
be 25 frames all with the same time stamp!
SiraView detects this and interpolates
time across the 25 frames, so that they
are evenly spaced.
To show you that this is happening, the
time stamp for the frame (displayed
under the video image) will be partially
highlighted in red.
The red digits are those that have been
interpolated – the white ones are those
directly decoded from the video frame. In
this way you can always tell what the
actual recorded time is, and you get an
indication that the recorder is storing
limited information.