SOLH264TX Broadcast Transmitter
H264TX, H264ENGTX, H264ENC
UNCLASSIFIED
Part A - User Guide
DS000091
Rev 1.2 2013-05-02
UNCLASSIFIED
Page 1-4
The major advantage of MPEG compared to other video and audio coding formats is that
MPEG files are much smaller for the same quality. This is because MPEG uses very
sophisticated compression techniques.
MPEG-2 (1995) covers generic coding of moving pictures and associated audio information.
MPEG-2 standard was considerably broader in scope and of wider appeal – supporting
interlacing and high definition. MPEG-2 is considered important because it has been chosen
as the compression scheme for over-the-air digital television.
MPEG-4 (1998): Coding of audio-visual objects. (ISO/IEC 14496) MPEG-4 uses further coding
tools with additional complexity to achieve higher compression factors than MPEG-2.
MPEG-4 Part 2: Aimed to improve efficiency at low bit-rates over MPEG-2 compression.
Advanced Simple Profile (ASP) encoding is used in Cobham SOLO products for low bit-rate,
long range links.
MPEG-4 Part 10: Otherwise known as H.264 or Advanced Video Coding (AVC). Increased
complexity, flexibility and efficiency over MPEG-4 Part 2; It defines a range of profiles for
different applications. High Profile encoding is used in the Cobham H264TX range due to its
flexible feature set, allowing for broadcast quality HD pictures at lower bit-rates than
comparable HD MPEG-2 systems.
1.3.3
Understanding COFDM
The modulation scheme that Cobham uses is Coded Orthogonal Frequency Division
Multiplexing (COFDM).
COFDM uses a very different method of transmission to older digital radio modulation
schemes and has been specifically designed to combat the effects of multipath interference
for mobile receivers.
COFDM is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier
modulation method. A large number of closely spaced orthogonal sub-carriers are used to
carry data. The data is divided into several parallel data streams or channels, one for each
sub-carrier. Each sub-carrier is modulated with a conventional modulation scheme (such as
quadrature amplitude modulation) at a low symbol rate, maintaining total data rates similar
to conventional
single-carrier
modulation schemes in the same bandwidth.
1.3.3.1
Summary of COFDM Advantages
Can easily adapt to severe channel conditions without complex time-domain equalization.
Robust against narrow-band co-channel interference.
Robust against inter-symbol interference (ISI) and fading caused by multipath
propagation.
High spectral efficiency as compared to conventional modulation schemes, spread
spectrum, etc.
Efficient implementation using Fast Fourier Transform (FFT).
Low sensitivity to time synchronization errors.
Facilitates single frequency networks (SFNs).
