5
TROUBLESHOOTING
Stuttering files during Playback
Irregular playback on single and multiple channels can be caused
by a number of conditions:
1. Uneven audio to video track lengths: Confirm the length of the
audio track to the length of the video track. The Visual Circuits
VCC4PRO driver, standard with all Visual Circuits boards and
digital servers, aggressively synchronizes the audio and video
data of the MPEG file to maintain Audio/Visual (AV) Sync. If
the MPEG file’s audio and video tracks are uneven in length,
the driver’s attempt to synchronize these uneven tracks will
result in poor performance. Mismatched AV track lengths will
result in overall degradation of system performance. Often a
"bad" file will cause uneven or stuttering playback on other
channels of the system as well. Through digital editing, MPEG
2 files can be "demultiplexed" (separating the audio from video
information). The audio and video tracks can then be edited to
match. The two tracks can then be "multiplexed" back together.
Always test files individually if a file (or system) is suspected
to have playback problems.
2. Mixed video only MPEG files with MPEG with video and audio
data: Confirm that all files on a particular channel are either
video only, audio only, or audio/video files. It is recommended
to have a "blank" audio track encoded with all MPEG files--
even if no audio is present on the source material. This will
ensure compatibility, if MPEGs with audio/video information
are introduced at a later date.
3. The bit rate of the MPEG files being played exceed the system
capabilities: The Visual Circuit MPEG decoder boards and
digital servers all have a maximum sustained bit rate that can
be delivered. Refer to the system capabilities above for basic
information. Always, consult your Visual Circuits
representative prior to encoding or designing your installation
if there are any questions.
