User manual

Introduction : Managing VCube Essentials Resources
Page 20
6.Current FPS
Note: The remaining counters not listed above either do not apply to VCube Essentials due to
the absence of an AJA® video board in the system or are not helpful in determining the cause of
poor playback.
Video and Audio Disk Read graphs
The Video and Audio Disk Read graphs show the delays between the moment a media frame is requested from a
disk volume and the moment it is available for use by VCube. These graphs therefore show the transfer time
before the media is decoded and placed into the Playback Buffer. So the number of Frames in the buffer itself has
no bearing on this information. As the bit-rate of the media increases so will the time it takes to read it from a disk
volume. The overall transfer time in milliseconds, displayed in the upper right corners of each graph as well as
plotted out in red, should never exceed the delay in milliseconds of the duration of one frame of video of the cur-
rent VCube playback engine. Just to be on the safe side it should even be considered that a safe ratio of Disk Read
delay to a single frame of video should be about half that of the time of a single frame to allow for occasional
media volume transfer bottlenecks. These bottlenecks may occur in very short periods of time but must never
exceed the remaining number of frames in the Playback Buffer. That is what the Playback Buffer is there for. Here is
a quick table to show the length of a single frame of video in milliseconds for each major frame rate and the subse-
quent approximate target Disk Read delays that should give reliable play out performance.
If the Disk Read delays systematically exceed the safe delay values then the Buffer will quickly empty out causing
stalling and skipped frames during playback.
Remedy: Use higher performance disk volumes that transfer the media files uninterrupted and fast enough for
VCube to process them and put them into the Play Buffer continuously or use a Media File with a lower bit rate.
Frame rate Milliseconds Safe Delay
24 41.67 20.83-30
25 40 20-30
29.97 33.37 16.68-28
Output Page - Playback Info Tab