4. New Instruments and Technical Tips

4. New instruments and technical tips
4. New Instruments and Technical Tips
As the number of conferences with multiple, interconnected locations increases, these events
have become a primary focus of our activities. For these events to succeed, participants must not
only be seen, but also be heard. Sound quality, therefore, is just as important a factor as video.
This section discusses audio equipment suitable for these conferences.
1. Instruments
The simplest system for DVTS is a DV camera, personal computer and network as illustrated
below (Fig. 4-1-1). However, external microphones (Ext. MIC) and audio amplifiers are required
for a comfortable, and audible, conference.
The simplest formats can handle only one visual and one sound source at the same time. An
analog-digital video converter (ADVC) is required to handle several visual sources, like operation
images or endoscopic video input.
The ADVC is an instrument that converts an analog video signal (S-video or composite) to
digital video with audio. Multiple video sources can be input and selected using video a mixer.
Chart 4-1-1 details the features and adaptations of video configurations with or without the
use of an ADVC.
Chart 4-1-1
Variation between Basic and Advanced configurations.
Analog- Digital
Video converter
Advanced
Basic
Video source limit
Adaptation for Live
Surgery
Use
Multiple
○
No use
One
×
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4. New instruments and technical tips
A. Advanced configuration（Fig. 4-1-2）
Fig4-1-2 Advanced Configuration
Instruments
1. Video Camera (No DV camera required)
2. DVTS PC (2units with IEEE1394 port)
3. Display (LCD, PDP or Projector)
4. Microphone (Unidirectional sensitivity and Power Switch)
5. Audio Amplifier
6. Analog-Digital Video Converter (ADVC)
7. Cables (Ethernet, Video, Audio, IEEE1394, Display, etc.)
Features:
This configuration provides ample performance for almost all cases, from small conferences to
large academic meetings. Since audio and video signals function independently, this system
provides complete control for both audio levels and video inputs. This configuration is
recommended for locations that send multiple visual sources like operation images.
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4. New instruments and technical tips
B. Basic configuration（Fig. 4-1-3）
Fig. 4-1-3 Basic Configuration
Instruments:
1. Digital Video Camera
2. DVTS PC (2 units with Ieee1394 port)
3. Display (LCD, PDP or Projector)
4. Microphone (Unidirectional sensitivity and Power Switch)
5. Audio Amplifier
6. Cables (Ethernet, Video, Audio, IEEE1394, Display, etc.)
Features:
This configuration does not provide adequate performance for use in important events or large
venues. Logistical problems exist, especially concerning audio. The Ext. MIC does not work
well, especially if both internal and external microphones are working simultaneously.
Since
this configuration is limited to one video source, images should be prepared and sent separately,
prior to the presentations. We do not recommend connecting the Ext. MIC directly into the “Ext.
MIC” port.
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4. New instruments and technical tips
Reference: Configuration for Live Surgery Demonstration（Fig. 4-1-4）
In live surgery demonstrations, two video sources are switched using a video mixer and
converted to a DV signal by the ADVC.
These signals typically include:
・ Operation images from laparoscopic surgery systems
・ Overview images from normal video cameras
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4. New instruments and technical tips
2. Sound Considerations
There are two major causes of sound problems, specific to teleconferences, described in the
following chart.
This section discusses echo noise (loop back noise, feedback noise)
Name
Case
Cause
Echo（Loop back, Feed back）
Packet Loss
Speaker’s voice from another site Voice comes on and off, stuttered
returns with delay
audio, robotic voice pattern
Voice returned through both
Packet loss (data loss) occurs over
microphone and speaker at site B
Internet connection (Bottle neck,
(Fig. 4-2-1)
routing, hardware problem etc).
Adjust
microphone
and
speaker Ask the network administrator to
Solution levels at site B to avoid catching optimize bandwidth, if possible.
sound from speakers.
*Mechanism of the Echo noise. (Fig. 4-2-1)
*Avoiding Echo Noise
The optimal configuration can control the microphone input level and the audio output levels
easily and simultaneously.
*Equipment Selection
¾
Audio Amplifier (must): A basic 4-channel amp is enough for small venues.
Used to adjust audio input and output levels. AUX port on
audio amplifier is useful for independent adjustment
between DVTS sound input and output.
¾
Microphone：bullhorn type（Unidirectional，Battery powered，with power switch）
Battery powered with power switch for convenience. Line
powered microphones require compatible devices.
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4. New instruments and technical tips
Trouble case 1: DV camera Problem
¾
Should the internal MIC on the DV camera be used?
¾
Can the microphone be directly connected to the DV camera?
The MIC on DV camera is usually omni directional and
auto gain controlled. It catches the sounds from speakers
with high sensitivity and causes some echo noise. The same
problem will occur if an ext. MIC plugged in directly.
Trouble case 2: MIC Problem
¾
Why we should not use MIC for TV conference.
MIC for TV conference is usually highly sensitive and
expected to use special systems designed for it, like an
installed echo canceller or auto gain controller.
For DVTS, it may cause echo noise or sound level
unbalance depend on the speaker’s position or the audio
speaker’s output level.
¾
Will an echo canceller solve echo problems?
Actually, an echo canceller is useful for reducing echo noise,
but it is required at each end of the connection. It will not
work well unless only the optimal settings for reducing
echo noise are used.
In the case of a conference with multiple locations, solving
sound problems with only an echo canceller is very difficult.
Configuration Self-Check
Usually, DVTS beginners do not recognize their own configuration errors and sound problems.
As a result, they may think the problems originated at the other location.
The multi-location teleconference system (QualImage: Quatre) does not return sound sent from
the originating location, thus we often hear echo noise from the other end without taking notice
of it.
The next page provides self-check procedures for DVTS configuration.
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4. New instruments and technical tips
Self-Check Using Acoustic Feedback.（for Basic configuration Fig. 4-1-3）
1. Set up your DVTS system, as it will actually be used, preferably at the venue.
（No need for global IP Address for DVTS PC.）
2. Set the audio speaker’s volume for normal use.
3. Turn off your external MIC and set the level to zero on the Audio Amplifier.
4. Send a DV stream from the local Transmission PC to the local Reception PC.
*Check point 1: Do you hear any acoustic feedback?
If you hear any acoustic feedback at this time:
*Check Audio amplifier – Is the DV camera cable connected?
*Verify that the DV camera internal microphone is muted.
If the Int. MIC is still working, try other DV camera model with a mutable MIC.
5. Turn on your External MIC.
*Check point 2: Is there any acoustic feedback?
If you connect the Ext. MIC to Ext. MIC plug on DV cam, you will hear acoustic feedback. This
problem is caused by automatic gain control on the DV cam and a very high input level. It is
difficult to solve this problem without an audio amplifier.
6. Gradually increase the MIC output level on Audio amplifier.
*Check point 3: Acoustic feedback should always be present at this time.
If there is no feedback, then the MIC or Speaker is not working properly.
Check them again.
7. Turn off your Ext. MIC when you hear feedback.
*Check point 4: Has feedback stopped?
Reducing the MIC output level on the audio amplifier will have the same effect.
8.Self-check completed.
Echo problems on DVTS are caused by the same mechanism described above. We believe DVTS
configurations that pass this self check will not create serious sound problems.
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