|
*7mSec
delay is made possible in the newer models AB5xx series while it is
90mSec on the older models AB4xx & AB3xx
Seven Things You Didn’t Know About
Wireless Broadcast Transmission
1. Wireless
broadcast transmission stability is easy (if you have the right
technology)!
The challenge of stability with wireless broadcast links is apparent
in unidirectional wireless systems that do not have acceptance
feedback. Unidirectional systems have no acknowledgement
confirmation or error notification from the receiver, which
compromises stability.
In ABonAir’s unique bidirectional links, both transmitter and
receiver can send and receive data and control information.
The technology enables the receiver to acknowledge each pixel
transmitted over the air, guaranteeing zero transmission errors. The
packet acknowledgment mechanism identifies errors and quickly fixes
them (by re-transmitting the corrupted data) before the frame is
presented. This enables ABonAir’s bidirectional solution to ensure
that all data is well received without errors, increasing stability
and robustness
2.
Transmission range can be extended through a wise antenna setup
Range variance is impacted by the number and locations of antennas,
and by the use of power amplifiers. ABonAir’s wide variety of
antennas and power amplifiers support any set-up, extending both
range and coverage. ABonAir systems reach up to 2.5 km (1.5 miles)
without power amplifiers in clear line-of-sight, and go beyond 2.5
km when boosted by power amplifiers.
3.Line of
Sight impacts transmission coverage
The declared range of systems is measured in clear lineof- sight
with no obstacles between the camera, and the receiver at the OB-van
or media center. The reason for clear line-of-sight measurements is
that testing and results can be duplicated anywhere. However, the
actual range is determined by the number of obstacles between the
transmitter and the receiver, and their material composition.
All radio systems obey basic physical rules: radio waves are blocked
by metals, water, concrete, trees, walls, trucks and more. In the
same way that shifting position by just one meter may allow for
better cellular phone reception, microwave camera link transmission
range is affected by signal blocking. Appropriate antenna
installation can solve signal blocking and easily increase coverage
and range dramatically.
4.Compression does not reduce video quality
Compression does not reduce video quality. Compression refers to the
removal of redundant information from the video.
The same image can be compressed from lightly (very high quality
video) to heavily (low video quality). Without compression an HD
video bandwidth requirement
uses an overwhelming ~2Gbps. Transmitting 2Gps is an impossible task
for wireless systems with a range of few hundred meters. Compression
is vital to keep picture quality high. Success hinges on compressing
as little as possible based on what the wireless link can maintain.
Uncompressed systems simply cut or remove quantities of information
and only transmit 400-500 Mbps, explaining low picture quality.
Bidirectional technology enables significantly increased bandwidth
efficiency. ABonAir’s bidirectional system constantly receives
feedback and acknowledgement,identifying conditions of wireless
capacity that allow it to adjust to the minimum possible
compression. The system utilizes the minimal compression required
for quality broadcasting while taking into consideration the
existing wireless conditions. In this way, ABonAir’s bidirectional
system compresses less while maintaining high picture quality (45dB
PSNR).
5.The catch
in short range transmitters
Short range systems, based on non-compressed technology, are
designed for a single room application and are mainly used in
production monitoring. They are price competitive,
but do not produce recording and broadcast quality. Unable to
maintain high picture quality, they delete a lot of picture data and
their range is limited. ABonAir systems provide high recording
quality for broadcast professionals, and are priced accordingly.
6.There is
a trade off between delay and compression
Wireless video delay derives from the system’s encoding and decoding
functions. A good encoder requires time to transmit the picture and
then compresses it. Delay is
not generated from the wireless transmission. The delay in wireless
transmission itself is less than 1msec. A compression CODEC is an
essential requirement in professional broadcasts as it reduces
content size to match the limited wireless capacity. Some wireless
transmitters transfer uncompressed video directly to reduce costs,
but this involves removing information from the picture in order to
save bitrate required from the radio. Uncompressed solutions are
based on a very high throughput wireless link.
This topology stretches wireless technology to its maximum and
reduces distance and coverage to a minimum guarantees errors during
the broadcast session, and compromises on picture quality.
Uncompressed transmission is only suitable for a very short range
(of several meters) with reduced picture quality.
ABonAir’s systems allow for a low 90msec delay, answering a crucial
need in live event coverage. ABonAir R&D teams constantly work to
improve the H.264 Encoder and reduce its delay, which naturally cuts
back on delay of the overall system.
7.The
superiority of automatic set up
Automatic frequency selection is a key benefit in the ABonAir
system. It dramatically improves transmission robustness, freeing
the cameraman to shoot video rather than deal with wireless
configurations. The system can automatically select the quietest,
most reliable channel available. Operational interferences is
handled by jumping to an alternative clear available frequency, by
contrast to other systems that cannot change frequency during
operation. ABonAir’s advanced system functions on algorithms that
automatically identify on-site frequency problems and perform the
necessary calculations for switching to another frequency,
transmitter and receiver within the same millisecond.
Three Things You Didn’t Know
About ABonAir |
