Design and Implementation of HDMI Transmitter

C.Srinivasan. Int. Journal of Engineering Research and Application www.ijera.com
ISSN : 2248-9622, Vol. 6, Issue 11, ( Part -5) November 2016, pp.09-12
www.ijera.com 9 | P a g e
Design and Implementation of HDMI Transmitter
1
C.Srinivasan, 2
K.ArulOli
1,2
Asst. Professor, Department of EEE, Kingston Engineering College, Vellore
ABSTRACT
The High-Definition Multimedia Interface is provided for transmitting digital television audio-visual signals
from DVD players, set-top boxes and other audio-visual sources to television sets, projectors and other video
displays. HDMI is used in various real time applications for transmitting and receiving audio-visual Signals. A
transaction level model of HDMI Transmitter is designed by using System Verilog. Transaction Level Modeling
methodologies promote the growth of System Level Description Language. This paper presents a HDMI
Transmitter Transaction Level Modeling Design which can be used to easily transform to HDL descriptions for
subsequent RTL (Register Transfer Level) Design.
Keywords: HDMI, System Verilog, RTL, HDL, Transaction Level Modelling
I. INTRODUCTION
High-Definition Multimedia Interface [1]
can carry high quality multi-channel audio data and
can carry all standard and high definition consumer
electronics video formats. HDMI can also carry
control and status information in both directions.
System Verilog has been the industry's
first unified Hardware Description and Verification
Language. It has became an official IEEE Standard
1800™ in 2003 under the development of
Accellera [3].. It can be built with or without
timing delay as a programmer’s view, or be built as
an accurate cycle Model [7]. System Verilog is
widely used to specify, design and implement
complex system.
II. HIGH-DEFINITION MULTIMEDIA
INTERFACE
HDMI System Architecture is defined to
consist of Sources and Sinks. A given device may
have one or more HDMI inputs and one or more
HDMI outputs. Each HDMI input on these devices
shall follow all of the rules for an HDMI Sink and
each HDMI output shall follow all of the rules for
an HDMI Source.
HDMI transmitter is a component that is
responsible for driving the four differential TMDS
channels output pairs into an HDMI output and for
clocking the data driven into those four output
pairs.
The features of HDMI 2.0 are listed below,
 Enables transmission of High Dynamic Range
(HDR) video
 Bandwidth up to 18Gbps
 4K@30/60 (2160p), which is 4 times the
clarity of 1080p/60 video resolution
 Up to 32 audio channels for a multi-
dimensional immersive audio experience
 Up to 1336kHz audio sample frequency for the
highest audio fidelity
 Simultaneous delivery of dual video streams to
multiple users on the same screen
 Simultaneous delivery of multi-stream audio to
multiple users (Up to 4)
 Support for the wide angle theatrical 21:9
video aspect ratio
 Dynamic synchronization of video and audio
streams
 CEC extensions provide more expanded
command and control of consumer electronics
devices through a single control point
Figure 1 HDMI 2.0 Block Diagram
As shown in Figure 1, the HDMI cable
and connectors carry four differential pairs that
make up the TMDS data and clock channels. These
channels are used to carry video, audio and
auxiliary data. In addition, HDMI carries a VESA
DDC channel. The DDC is used for configuration
and status exchange between a single Source and a
RESEARCH ARTICLE OPEN ACCESS

single Sink. The optional CEC protocol provides
high-level control functions between all of the
various audiovisual products in a user’s
environment
2.1 Brief Description of the HDMI
In HDMI system, all Video data can have
a pixel size of 24, 30, 36 or 48 bits, and which that
at the default 24-bit color depth is carried at a
TMDS clock rate equal to the pixel clock rate. To
keep the balance of system rule, those higher color
depths are carried using a correspondingly higher
TMDS clock rate. Video formats with TMDS rates
below 23MHz can be transmitted using a pixel-
repetition scheme. The video pixels can be encoded
in either RGB, YCBCR 4:4:4 or YCBCR 4:2:2
color space[8]. As we know, Basic audio contains a
single format IEC 60938 L-PCM audio stream at
sample rates of 32kHz, 44.1kHz or 48kHz. HDMI
can optionally carry such audio at sample rates up
to 192KHz and also has 3 to 8 audio channels, and
support to carry an IEC 61937 compressed (e.g.
surround-sound) audio stream at bit rates up to
24.376Mbps. HDMI can also carry from 2 to 8
channels of One Bit Audio and a compressed form
of One Bit Audio called DST.
2.2 Packing and Encoding
An HDMI physical link includes three
TMDS Data channels and a single TMDS Clock
channel as shown in Figure 2. The TMDS Clock
channel constantly runs at a rate proportional as the
pixel rate of the transmitted video. Each of the
three TMDS data channels transmits a 10-bit
character during every cycle of the TMDS Clock
channel. This 10-bit word is encoded using one of
several different coding techniques.
Figure 2 HDMI Encoder/Decoder Overview
As described at Figure 2, the input data
stream to the Source’s encoding logic module will
contain video pixel (e.g. B), packet (e.g. Audio
Sample) and control data. The source transmitter
encodes 2 bits of control data, 4 bits of packet data
or 8 bits of video data per TMDS channel to 10 bits
output, and the Source encodes one of these data
types or encodes a Guard Band character on any
given clock cycle.
As for transmission audio and auxiliary data across
three TMDS channels, HDMI uses a packet
structure. For the purpose of the higher reliability
required of audio and control data, this data is used
with a BCH error correction code and is encoded
with a special error reduction coding method to
produce the 10-bit output word that is transmitted
on the TMDS channels.
III. SYSTEM VERILOG FEATURE
System Verilog provide some key elements
for hardware and system-level modeling or UVM
style verification. Object-Oriented Programming
(OOP) lets you create complex data types and tie
them together with the routines that work with
them. You can create test benches and system-level
models at a more abstract level by calling routines
to perform an action rather than toggling bits.
When you work with transactions instead of signal
transitions, you are more productive.
Transaction Level Model (TLM) is a term
used to identify a reference model that implements
the required functionality at a very high level of
abstraction [3]. Given the RTL code is written at a
low level of abstraction, TLM's are usually written
more quickly and efficiently capture the expected
function of the device. System Verilog support to
use a Extensible verification method library such as
UVM and VMM for verification and modeling.
IV. FUNCTIONAL TRANSMITTER
MODEL
This part presents a functional level model
of HDMI Transmitter. The model is divided into
separate sections according to different functions,
and the module includes various user-definable
switches. We built the whole model by the method
of OPP and TLM, so it either has a feature of
clearly and easily maintained structure, or
correspond the mainstream standard modeling
methods.
4.1 The Overall Design
The overall design of the model is as follows:
The whole HDMI transmitter model is
divided into several classes. Env which is called
environment is a large container of whole
transmitter. If this model use for the HDMI entire
model as a modeling or verification components, it
can be reused from this level. The agent packs
those parts which interact with the external

interface such as a driver and a monitor as a class.
Sequencer is as sequence generator, controlling that
which of the transaction should be sent to the driver
depending on the needs of driver. Driver is the Bus
Function Model (BFM), whose function is to
abstract data from the upper streams into the signal
level and sent them to the interface.
Transaction level is the core of TLM
transport. The flow of data across internal model is
based on packet units.. Thus the core of the
transmitter is the class of transaction and its
member functions, which is used to capture the
data and drive it out according to the protocol. The
config part is also a config type class which
contains all the parameters that need to set for the
model.
4.2 The Data Encoding Design
The encoding module put into the
interface, and encoding process is designed full
accordance with protocol requirements. The
upstream module drives the transaction into
interface, and spilt into three-way 8 bit RGB, 4bit
auxiliary data or 2bit control data in different time.
Video Data Periods use the way of
Transition Minimized Differential encoding to
transfer eight bits data in each channel, a total of
24, showing a video pixels. Data Island Periods
using a similar method with minimized differential
coding, is called TMDS Error Reduction Coding
(TERC4), each channel transmitting four data per
clock cycle, a total of two data transfer. Control
Periods, transfer two data per channel, a total of six
bits data which are HSYNC, VSYNC, CTL0,
CTL1, CTL2 and CTL3. So, in each TMDS clock
cycle, use Transition Maximized encoding for
those 2bits data.
4.3 The Data Generating and Scheduling Design
HDMI transmitter is designed mainly lies
in the capture of upstream video and audio data and
packing by the protocol. The modeling process is
using TLM model which a transaction is a
transmission unit. So a frame image is a
transaction, and all the data which needs to transmit
must put in this transaction.
Firstly, transaction was defined as a class, which
has three member functions, respectively using for
generating video data, generating data island and
group packages output. These three functions are
all nested different classes and functions. Video
generation module generates HSYNC, VSYNC,
DE and other signal which are used to constitute a
frame image. When DE signal is valid, that is,
HSYNC and VSYNC invalid video period, then the
three channels transmit video data. When DE signal
is invalid, that is, HSYNC and VSYNC valid for
the data island period, then transmit the auxiliary
data which is generated by data island packet
module, and it contains audio sample package and
other supplementary information package. In the
middle of the data island period and the video
period must have a control period, and HSYNC and
VSYNC signal are transmitted outward through the
control period. The entire process of data
scheduling is done by a function of packing data
out.
V. SYSTEM MODEL VERIFICATION
The way to verify the HDMI transmitter
model was using a proven HDMI receiver's IP, and
comparing the video and audio data whether can
complete transmission by connecting and some
related configuration. Video transmission use the
color bar, and it allows you to quickly check the
source, transmission, sink, signal black and white
level display prospective, especially mainly use to
confirm the entire signal flow in the color
encoding and decoding is whether normal or not. In
this test case, we choose the video format of
640x480p.As show in Figure 3(a), we firstly use
the waveform of channel 0 outputs to show that
three channels corresponding to the time sequence
as their rule. In addition, comparison of channel 0
video data of transmitter and receiver pre-encoded
data indicate the correctness of video data transmits
as Figure 3(b). Finally, we show a comparison of
the frame picture of color bar as Figure 3(c).
(a) Waveform of Transmitter Output before
Encoding
(b) Video Data Waveform of Transmission and
Recovery

c) A Frame Colour Bar of 640x480p Format
Figure 3 HDMI Transmitter Model Video
Verification
In the audio transmission verification
section, we stored a sampling rate of 32 KHz audio
data in a file, and read from transmitter model. The
model grouped the audio data in accordance with
IEC60938 package type and then grouped frame by
protocol of HDMI, in conjunction with various
auxiliary information packet transmission, such as
audio Clock Regeneration packet and General
Control packet, which is used to restore the audio
clock or control the audio mute and so on. As
Figure 3(a), it shows that audio sample data
transmit at the data island period and audio
frequency is regenerated by receiver. According to
the equation of 128*fs at two end, we used a period
of signal AUD_NFS to calculate the regenerated
frequency was 32 KHz. In order to verify the
correctness of transmission, we stored the audio
data in two files for comparison, as specified in
Figure 3 (b):
(a) Waveform of video data
(b) Waveform of Audio Data
Figure 4 HDMI Transmitter Model Audio
Verification
VI. CONCLUSION
In this paper, it completes a model in
HDMI transmitter by high-level object-oriented
modeling approach. This article in-depth studies
the new features in System Verilog language for
modeling, and analyzes the principles and
algorithms of HDMI Audio and Video
Transmission. It accomplishes a non-timing
reusable transaction level model which is not only
supported 32 video format types and 7 audio types
but also 300% faster than RTL model.
REFERENCES
[1]. www.hdmi.org “HDMI Specification
1.3a”
[2]. Jiang Xiong, Qing Ming Yi and Min Shi,
Applied Mechanics and Materials, p.4094-
4097(2013).
[3]. Martin Keaveneyt, Anthony McMahont,
ISSC 2008, Galway, June 18-19, p.323-
330 (2008).
[4]. Lingling Chai, Zheng Xie and Xin’an
Wang, 2014 IEEE International
Conference on Electron Devices and
Solid-State Circuits, p.389(2014).
[5]. Sang-Bong Byun, Young-Hyung Kim,
International Journal of Control and
Automation, p.191-200(2013).
[6]. Jian Wang, Hong Wang, and Zhijia Yang,
ASICON 2009 Proceedings, 2009 8th
IEEE International Conference on ASIC,
p.97-100(2009).
[7]. Gao Yingke, Wu Diancheng and Li
Quanquan, 2013 IEEE 10th International
Conference on ASIC, ASICON
2013(2013).
[8]. Hitachi Electronics, Panasonic
Corporation and Philips Electronics, High-
Definition Multimedia Interface
Specification Version 1.4b, p.10(2009).

Design and Implementation of HDMI Transmitter

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