ETSI TS 103 544-2 V1.3.1 (2019-10)

ETSI TS 103 544-2 V1.3.1 (2019-10)






TECHNICAL SPECIFICATION
Publicly Available Specification (PAS);
Intelligent Transport Systems (ITS);
®
MirrorLink ;
Part 2: Virtual Network Computing (VNC)
based Display and Control
CAUTION
The present document has been submitted to ETSI as a PAS produced by CCC and
approved by the ETSI Technical Committee Intelligent Transport Systems (ITS).
CCC is owner of the copyright of the document CCC-TS-010 and/or had all relevant rights and had assigned said rights to
ETSI on an "as is basis". Consequently, to the fullest extent permitted by law, ETSI disclaims all warranties whether express,
implied, statutory or otherwise including but not limited to merchantability, non-infringement of any intellectual property rights of
third parties. No warranty is given about the accuracy and the completeness of the content of the present document.

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2 ETSI TS 103 544-2 V1.3.1 (2019-10)



Reference
RTS/ITS-98-2
Keywords
interface, ITS, PAS, smartphone, USB

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The copyright and the foregoing restriction extend to reproduction in all media.
© ETSI 2019.
© Car Connectivity Consortium 2011-2019.
All rights reserved.
ETSI logo is a Trade Mark of ETSI registered for the benefit of its Members.
MirrorLink® is a registered trademark of Car Connectivity Consortium LLC.
RFB® and VNC® are registered trademarks of RealVNC Ltd.
UPnP® is a registered trademark of Open Connectivity Foundation, Inc.
Other names or abbreviations used in this document may be trademarks of their respective owners.
DECT™, PLUGTESTS™, UMTS™ and the ETSI logo are trademarks of ETSI registered for the benefit of its Members.

3GPP™ and LTE™ are trademarks of ETSI registered for the benefit of its Members and
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of the oneM2M Partners.
®
GSM and the GSM logo are trademarks registered and owned by the GSM Association.
ETSI

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3 ETSI TS 103 544-2 V1.3.1 (2019-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definition of terms, symbols and abbreviations . 7
3.1 Terms . 7
3.2 Symbols . 7
3.3 Abbreviations . 7
4 Introduction . 8
5 Managing a VNC session . 9
5.1 Identifying Remote Applications and the VNC Server . 9
5.2 Launching the VNC Session . 9
5.3 Intentionally Terminating the VNC Session. 9
5.4 Unintentionally Terminating the VNC Session . 10
5.5 Testing Considerations . 10
6 Traditional VNC Protocol Phases . 10
6.1 General . 10
6.2 Handshaking Phase. 11
6.3 Initialization Phase . 12
6.4 Framebuffer Update and Event Phase . 13
7 VNC MirrorLink Extension Messages . 16
7.1 General . 16
7.2 ByeBye Message . 17
7.3 Display Configuration Messages . 18
7.3.1 General . 18
7.3.2 Framebuffer Scaling (VNC Server) . 22
7.3.3 Framebuffer Scaling (VNC Client) . 23
7.3.4 Handling of Different Framebuffer Aspect Ratios . 23
7.3.5 Handling of Server Pixel Aspect Ratios . 24
7.3.6 Handling of Application, Framebuffer and Display Orientation . 24
7.4 Event Configuration Messages . 25
7.5 Event Mapping Messages . 29
7.6 Device Status Messages . 30
7.7 Content Attestation Messages . 34
7.8 Framebuffer Blocking Notification . 37
7.9 Audio Blocking Notification . 43
7.10 Touch Event . 46
8 Additional Encodings and Pseudo Encodings . 48
8.1 General . 48
8.2 MirrorLink Pseudo Encoding . 49
8.3 Context Information Pseudo Encoding . 49
8.4 Desktop Size Pseudo Encoding . 50
8.5 Scan Line based Run-Length Encoding . 51
8.6 VA H.264 Encoding . 52
8.6.1 Overview . 52
8.6.2 Theory of operation . 53
Annex A (normative): Knob Configuration . 59
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4 ETSI TS 103 544-2 V1.3.1 (2019-10)
Annex B (normative): Key Event Mapping . 60
Annex C (normative): Language Sets . 63
C.1 Basic Set Latin-1 . 63
Annex D (informative): Authors and Contributors . 64
History . 65


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5 ETSI TS 103 544-2 V1.3.1 (2019-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Intelligent Transport Systems
(ITS).
The present document is part 2 of a multi-part deliverable. Full details of the entire series can be found in part 1 [i.1].
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in Clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
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6 ETSI TS 103 544-2 V1.3.1 (2019-10)
1 Scope
®
The present document is part of the MirrorLink specification which specifies an interface for enabling remote user
interaction of a mobile device via another device. The present document is written having a vehicle head-unit to interact
with the mobile device in mind, but it will similarly apply for other devices, which provide a colour display, audio
input/output and user input mechanisms.
The contents of the MirrorLink Server device's screen are transferred to the MirrorLink Client device. The control
inputs are transferred from the MirrorLink Client to the MirrorLink Server. Screen copy methods can be used to copy
the content of the MirrorLink Server's framebuffer to the MirrorLink Client's display. The copy operation can include
rotation or colour conversion. The frame buffer is used as an abstraction layer, allowing any changes to the applications
and services running on the mobile device to be avoided. For this purpose, the Virtual Networking Computing (VNC)
protocol is used.
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long-term validity.
The following referenced documents are necessary for the application of the present document.
[1] IETF RFC 6143: "The Remote Framebuffer Protocol", March 2011.
NOTE: Available at https://tools.ietf.org/html/rfc6143.
®
[2] Bluetooth Specification: "Hands-free Profile", Audio, Telephony, and Automotive Working
Group, Revision 1.7.2, January 21, 2019
NOTE: Available at https://www.bluetooth.org/docman/handlers/downloaddoc.ashx?doc_id=457090.
[3] ETSI TS 103 544-3 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 3: Audio".
[4] ETSI TS 103 544-9 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 9: UPnP Application Server Service".
[5] ETSI TS 103 544-10 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 10: UPnP Client Profile Service".
[6] ETSI TS 103 544-26 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink® ; Part 26: Consumer Experience Principles and Basic Features".
[7] X Consortium Standard: "X Window System Protocol", X Version 11, Release 6.9/7.0.
NOTE: Available at ftp://ftp.x.org/pub/X11R7.0/doc/PDF/proto.pdf.
[8] Recommendation ITU-T H.264 (04-2017): "Advanced video coding for generic audiovisual
services".
NOTE: Available at https://www.itu.int/rec/T-REC-H.264-201704-S/en.
[9] ISO 639-1: "Codes for the representation of names of languages -- Part 1: Alpha-2 code".
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7 ETSI TS 103 544-2 V1.3.1 (2019-10)
[10] ISO 3166-1: "Codes for the representation of names of countries and their subdivisions --
Part 1: Country codes".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long-term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TS 103 544-1 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 1: Connectivity".
[i.2] US Department of Homeland Security: "Emergency Alerts".
NOTE: Available at https://www.ready.gov/alerts.
[i.3] IANA, Protocol Registries, Remote Framebuffer (RFB) assignments.
NOTE: Available at https://www.iana.org/assignments/rfb/rfb.xhtml.
[i.4] ISO/IEC 10646:2014: "Information technology -- Universal Coded Character Set (UCS)".
[i.5] ETSI TS 103 544-22 (V1.3.1): "Publicly Available Specification (PAS); Intelligent Transport
Systems (ITS); MirrorLink®; Part 22: Android Specific Specifications enabling AIDL-based
MirrorLink® Applications".
3 Definition of terms, symbols and abbreviations
3.1 Terms
For the purposes of the present document, the following terms apply:
pointer event: touch screen action in which the user touches the screen with one (virtual) finger only at a single
location
touch event: touch screen action in which the user touches the screen with two or more separate fingers at different
locations
NOTE: touch events are used to describe more complex touch action, like pinch-open or pinch-close
3.2 Symbols
Void.
3.3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
A2DP Bluetooth Advanced Audio Distribution Profile
API Application Programming Interface
ARGB Alpha-Red-Green-Blue
BT Bluetooth
BVRA Bluetooth Voice Recognition Activation
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DAP Device Attestation Protocol
FAR Framebuffer Aspect Ratio
FBU FrameBuffer Unit
FEMA Federal Emergency Management Agency
HSML High-Spead Media Link
IANA Internet Assigned Numbers Authority
ISO International Standards Organization
NAL Network Abstraction Layer
PAR Pixel Aspect Ratio
PIN Personal Identification Number
PPS Picture Parameter Set
RFB Remote Framebuffer
RGB Red-Green-Blue
RLE Run-Length Encoding
RTP Real-time Transport Protocol
SPS Sequence Parameter Set
TCP Transmission Control Protocol
TV TeleVision
UDP User Datagram Protocol
UI User Interface
UPnP Universal Plug and Play
URL Universal Resource Locator
US United States
USB Universal Serial Bus
UTF Unicode Transformation Format
VA Video Audio
VCL Video Coding Layer
VNC Virtual Network Computing
4 Introduction
The Virtual Networking Computing (VNC) uses the Remote Framebuffer Protocol (RFB) as a simple protocol for
remote access to any sort of framebuffer-based user interface. The remote endpoint is called the VNC Client, whereas
the endpoint driving the framebuffer is called the VNC Server. In the MirrorLink context, the VNC Client resides in the
vehicle head-unit (MirrorLink Client) and the VNC Server is in the mobile device (MirrorLink Server). The VNC
Client will show the remote display either on the entire local display or on a subset of it, as shown in Figure 1.

Figure 1: MirrorLink VNC Setup
The command and control input is handled as part of the VNC protocol by key and pointer events. A key or pointer
event on the MirrorLink Client will be signalled to the MirrorLink Server via a specific key symbol value, which
uniquely identifies the event. The mobile device and/or its application will not necessarily support all possible keys
defined. Some applications may even have a dynamic behaviour on the selection of key inputs they expect.
The RFB protocol originates from the desktop computing world and has been designed as a thin client protocol, i.e. it
assumes a VNC Client with only a few requirements, and a VNC Server having access to more processing capabilities.
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9 ETSI TS 103 544-2 V1.3.1 (2019-10)
The protocol allows the VNC Client to be as simple as possible. In the MirrorLink context this assumption needs to be
reconsidered, as mobile devices are experiencing performance limitations as well.
The MirrorLink Client shall implement the VNC Client functionality.
The MirrorLink Server shall implement the VNC Server functionality.
5 Managing a VNC session
5.1 Identifying Remote Applications and the VNC Server
The identification of remote VNC based applications and of the VNC Server is described in [4].
5.2 Launching the VNC Session
The VNC Server start-up is automatically facilitated via UPnP. The MirrorLink Server's VNC Server shall be running,
when launching any application in response to a UPnP TmApplicationServer:1 service LaunchApplication action, as
defined in [4]. The LaunchApplication action shall return with a URL to the VNC Server, hosting the VNC session.
If the returned URL is already used from any established VNC session, this session will continue without any change.
Otherwise a new VNC session shall be established, given the following steps:
1) VNC Server shall listen for the VNC Client to make TCP connection at the provided URL.
2) VNC Client shall make a TCP connection to the provided URL.
3) VNC Server and Client shall initialize the VNC session according to the VNC protocol.
5.3 Intentionally Terminating the VNC Session
A VNC session can be terminated any time from both the VNC Server and Client. This mechanism is not meant to
handle error situations, which require immediate action from both the VNC Server and Client (use the unintentional
termination mechanisms instead). In particular, intentional termination shall be used, if the VNC session is terminated
based on an intended user action resulting in a termination of the VNC session.
The VNC Client shall terminate a VNC session using the VNC ByeBye message, as given below:
1) VNC Client shall send a VNC ByeBye message. The VNC Client shall not send any further VNC message,
after sending the VNC ByeBye message. The VNC Client should ignore all incoming VNC messages, after
sending a VNC ByeBye message.
2) VNC Server shall respond with a VNC ByeBye message.
3) VNC Client shall disconnect the TCP connection. The VNC Client should disconnect the TCP connection, if it
does not receive a VNC ByeBye message back within 5 s.
4) VNC Server should disconnect the TCP connection on detection of the VNC Client TCP disconnect or 5 s
after sending the VNC ByeBye message, whatever comes first.
The VNC Client shall wait with the VNC ByeBye message, if it has an outstanding UPnP LaunchApplication action
until it has received the corresponding UPnP response. This avoids any potential race condition problems.
The VNC Server shall terminate a VNC session, using the VNC ByeBye message, as given below:
1) VNC Server shall send a VNC ByeBye message. The VNC Server shall not send any further VNC message,
after sending the VNC ByeBye message. The VNC Server should ignore all incoming VNC messages, after
sending a VNC ByeBye message.
2) VNC Client shall disconnect the TCP connection.
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3) VNC Server should disconnect the TCP connection on detection of the VNC Client TCP disconnect or 5 s
after sending the VNC ByeBye message, whatever comes first.
It is up to the MirrorLink Client, whether a new VNC session is launched immediately, after the old one has been
terminated, from the VNC Client or Server.
The MirrorLink Client should send a UPnP TmApplicationServer:1 service TerminateApplication action for the stand-
alone VNC Server, if the VNC Client has previously launched it for the terminated session.
Terminating a VNC session shall not impact the application status of any application on the MirrorLink Server. If the
MirrorLink Client decides to re-establish the VNC session, it shall follow the steps given in Clause 5.2.
If MirrorLink Server has intentionally terminated the VNC session, the MirrorLink Client should provide a mechanism
to start a VNC session again. If the MirrorLink Client decides to re-establish the VNC session, it shall follow the steps
given in Clause 5.2.
In case the MirrorLink Client has intentionally terminated the VNC session, the MirrorLink Client shall wait until it
received the VNC ByeBye message from the MirrorLink Server (or it ran into the disconnect timeout), prior sending any
new UPnP Launch Application message.
In case the MirrorLink Server has intentionally terminated the VNC session, it shall wait until it detects the TCP
disconnect (or it ran into the disconnect timeout), prior responding to any new UPnP Application launch action or it
shall use a different URL than the previous VNC session.
5.4 Unintentionally Terminating the VNC Session
Unintentional termination of the VNC session may happen any time due to error conditions. In case of unintentional
termination of the VNC session, the respective VNC Server or Client will disconnect the TCP connection. The
respective counterpart should disconnect as well.
If the MirrorLink Client decides to re-establish the VNC session, it shall follow the steps given in Clause 5.2.
To avoid the VNC Server or Client persisting in a TCP TIME-WAIT time-out loop, as a result of an unintentional
active disconnect, the TCP socket should be established using the SO_REUSEADDR option (or similar platform
specific variants), allowing the operating system to reuse a port address, even it is currently in the TIME-WAIT state or
the VNC Server should use a different, unaffected port number.
5.5 Testing Considerations
If the MirrorLink Client is in a dedicated testing state (as part of the MirrorLink Certification), it shall launch a new
VNC session (either initiated automatically or manually from the user), whenever the VNC Server has intentionally
terminated the VNC session.
If the MirrorLink Client is in a dedicated testing state (as part of the MirrorLink Certification), it shall launch a new
VNC session (either initiated automatically or manually from the user), whenever the VNC Server has unintentionally
terminated the VNC session.
6 Traditional VNC Protocol Phases
6.1 General
After the connection between the VNC Server and Client has been established, the VNC protocol processing will start
according to the VNC specification. The VNC protocol consists of three main steps:
1) Exchange of handshaking messages. After the handshaking phase, the VNC connection parameters are
negotiated and the connection is established.
2) Exchange of initialization messages. After this phase, both ends have agreed on all needed parameter for the
following operational phase.
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11 ETSI TS 103 544-2 V1.3.1 (2019-10)
3) VNC Client to Server and VNC Server to Client messages are used to reflect changes of the framebuffer
content on the local endpoint and user interaction on the remote endpoint.
These three VNC protocol phases are specified in more detail in the following clause.
6.2 Handshaking Phase
The handshaking phase defines a couple of messages, which are exchanged between the VNC Client and the VNC
Server, as shown in the Figure 2. In general, the VNC Server presents its capabilities and the VNC Client selects the
best option with regard to its own capabilities.

Figure 2: VNC Handshaking Phase
The Table 1 parameters shall be supported from the VNC Client and the Ser
...