1394贸易协会AV/C面板子单元规范1.1

bluetooth

AVRCP

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"该文档是AV/C Panel Subunit Specification 1.1版，由1394 Trade Association赞助并发布，旨在定义一个在IEC61883规定的Function Control Protocol上运行的Panel子单元模型和命令集。该规范主要涉及通过蓝牙AVRCP（音频/视频远程控制配置文件）传输设备GUI信息，用于远程控制，包括用户命令和GUI数据的传输机制。关键词涵盖音频、视频、1394数字接口、GUI、OSD、屏幕显示、Panel、菜单和遥控器控制。" 详细知识点： 1. **1394 Trade Association**：这是一个专注于1394（也称为FireWire或i.Link）技术的行业协会，该协会发布了这份技术文档，并规定了成员可以复制和使用该文档的条件。 2. **AV/C Panel Subunit**：这是规范的核心，指一种在1394接口上的子单元，它提供了图形用户界面（GUI）信息，主要用于设备的远程控制功能。面板子单元可能是电视、播放器等多媒体设备的一部分，允许用户通过远程控制进行操作。 3. **Function Control Protocol**：这是IEC61883标准的一部分，定义了如何在1394网络上控制音视频设备。在此协议上运行的Panel子单元能实现更高效、标准化的设备控制。 4. **GUI (Graphical User Interface)**：用户界面，是用户与设备交互的方式，这里特指设备的屏幕显示，如菜单、设置选项等。 5. **OSD (On-Screen Display)**：屏幕显示，通常指在视频或电视屏幕上显示的附加信息，如菜单、状态指示、文字信息等，用户可以通过遥控器进行操作。 6. **AVRCP (Audio/Video Remote Control Profile)**：蓝牙AVRCP是蓝牙技术联盟定义的一个配置文件，用于无线控制音频和视频设备，例如播放、暂停、快进、选择曲目等功能。 7. **User Commands and GUI Data Transmission**：用户命令和GUI数据传输机制是该规范的重要组成部分，它定义了如何通过蓝牙AVRCP将用户的控制指令从遥控器发送到设备，并将GUI信息从设备传回遥控器的显示屏幕。 8. **Keywords**：这些关键词表明文档内容涵盖了音视频处理、1394数字接口技术、遥控操作的多个方面，是理解和应用该规范的关键。 9. **Copyright and Permissions**：文档的版权由1394 Trade Association持有，允许成员复制和使用，但严禁未经授权的商业使用。这份文档对于理解如何通过1394接口和蓝牙AVRCP进行多媒体设备的远程控制具有重要价值，特别是对于开发和设计相关硬件或软件的工程师来说，它是不可或缺的技术参考资料。

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AV/C Panel Subunit Specification 1.1 TA Document 2001001, May 8, 2001

4.2 Panel Subunit Logical Model

Figure 4.3 – Panel subunit logical model

The panel subunit may support multiple asynchronous outputs, used for GUI data transmission, depending

on implementation. In case of the direct mode, where the panel subunit itself transfers GUI data, the panel

subunit has at least one source plug. In case of the indirect mode, where the panel subunit doesn’t care

about GUI data, the panel subunit has no source plug.

4.3 UI data transfer mode

A Panel subunit has two UI data transfer modes.

1) Direct mode: allows Panel subunit to transfer UI data and to receive user manipulations. The

controller constructs UI from the obtained UI data, and conveys user operations to a target by

mainly USER ACTION commands, and sometimes PASS THROUGH commands. For details,

refer to section 4.4.

2) Indirect mode: allows Panel subunit to receive user manipulations but the panel subunit doesn’t

care about UI data to be displayed on the controller screen. The GUI image might be transmitted

to the display device by being multiplexed with the stream data transmitted from other subunit

than the panel subunit in the target device. The Panel subunit controller conveys user operations to

the target by only PASS THROUGH commands, and works simply like a remote commander of

the target device. For details, refer to section 4.5

A target shall be implemented with only one of the above UI data transfer modes.

The controller can identify which mode the panel subunit supports, by using the following procedure;

Direct mode: The panel subunit supports GUI UPDATE status or control command. If the

controller wants to check the capability of the panel subunit, it issues the GUI UPDATE status

command. And the response is NOT “NOT IMPLEMENTED” response, then the panel subunit

supports the direct mode. The controller can also check the GUI UPDATE control command,

skipping the status command, if it wants to check the mandatory display capability, e.g. 640 x 480

pixels GUI resolution.

Figure 4.4 – Start procedure for direct mode

Controller Target

Panel Subunit

The controller start working

with the panel subunit

response

GUI_UPDATE(open)

response

GUI_UPDATE status cmd.

Return the capability

The controller checks

capability of Panel subunit

Panel Subunit

…

Source

Plugs

Destination

Plug

TA Document 2001001, May 8, 2001 AV/C Panel Subunit Specification 1.1

2) Indirect mode: The panel subunit doesn’t support GUI UPDATE status nor control command.

First, the controller issues the GUI UPDATE status command. Then if the response is “NOT

IMPLEMENTED”, the panel subunit doesn’t support direct mode. So the controller will check

whether it supports the indirect mode by using GENERAL INQUIRY command for PASS

THROUGH command. If the response is “IMPLEMENTED”, the panel subunit supports the

indirect mode.

Figure 4.5 – Start procedure for indirect mode

4.4 Direct mode

In the direct mode, the panel subunit provides the UI data from its source plug.

The direct mode allows controllers to get the UI data from the Panel subunit using asynchronous

connection to, construct a user interface. In this case the controller works as an asynchronous connection

controller (AC-CTR) as well as a panel subunit controller (PS-CTR). AC-CTR is used to establish an

asynchronous connection via some connection procedure between the target (containing the panel subunit)

and the controller that has the capability of rendering and displaying UI.

The user manipulates the user interface on the controller’s screen or operates a button on a physical or

logical remote commander of the controller, and then the controller sends USER ACTION or PASS

THROUGH commands back to the panel subunit. In response to these commands, the panel subunit

performs some action(s) and sends UI updates to the controller if needed.

Even though there may be several panels, or menus, in a target device, the device has only one panel

subunit and the UI data structures allow this single subunit to represent and manage any number of separate

control panels for its device. A single control panel mayyy have sets of GUI elements which trigger actions

in different subunits and/or the unit. For example, a panel for a VCR may have the typical Stop, Play and

Record buttons which affect the VCR subunit, and it may also have a set of preset buttons which affect the

tuner subunit. It is also possible that the control panel has GUI elements which don’t affect any other

subunits; they cause a change in the state of the unit. A text entry field which allows the user to store a

preferred name for the device would be such an example.

The collection of GUI elements which appear in a panel is determined by the designer of the panel; there

are no restrictions on this collection other than the product specifications and the common sense of user

interface design.

In this mode the panel subunit can have only one controller for each source plug, and each source plug

works according to commands of the owner associated with that source plug.

Controller Target

Panel Subunit

The controller start working

with the panel subunit

Response (implemented)

General inquiry

(PASS THROUGH)

response

PASS THROUGH

Return the capability

The controller checks

capability of Panel subunit

The controller notice target

supports indirect mode.

response (not implement)

GUI UPDATE status cmd.

Return the capability

AV/C Panel Subunit Specification 1.1 TA Document 2001001, May 8, 2001

4.4.1 GUI Layout and Prese ntation for direct mode

The layout rules of GUI elements are based on geometric coordinates and use relative x, y values for each

GUI element. GUI elements are arranged in a hierarchy and positioned relative to their parents. The parents

of individual GUI elements are either groups or panels; the parent of a group is the panel in which it is

defined. Panels have no parent – their placement on screen is determined by the controller.

The following diagram illustrates this relationship:

Figure 4.6 – Relationship among Panel, Group and GUI elements

The panel subunit

suggests

a preferred layout, which is encoded into the GUI data structures. However, the

controller may tailor the presentation of GUI elements based on its own limitations, such as the screen size,

the ability to display graphics or text only, etc.

This mechanism provides a very flexible layout and display model, from text-only through high quality

graphics presentation. As a result, as long as there is some kind of display available to the controller, this

model can guarantee some kind of presentation to the user.

However, the controller cannot provide guarantees over the graphical rendition of GUI elements, since their

representation may be changed due to lack of display screen space, color and transparency capabilities, or

other resource limitations. The controller may discard some data or elements right after they are received.

Furthermore, application software can create different representations of the GUI, using the GUI elements

as “hints”. For instance the application software can display quite deferent look and feel using icons that is

fetched from the panel subunit. However the controller should try to preserve the appearance of GUI

elements as much as it can, based on its rendering capabilities.

4.4.2 Interactions between controller and target

There are two interactions: one between the user and the controller, and the other between the controller

and the target.

The controller communicates with the user via the input and output devices of (typically) the device upon

which the controller is executing. This I/O communication may be done in a controller-implementation-

dependent manner (e.g. IR remote, keyboard and mouse, television or PC display, small text-only screen,

etc.). The target controls itself in a target-implementation-dependent manner. The protocol described in

this section is structured so that a controller may be defined in a generic manner. That is, a controller does

not

have to be implemented with knowledge of a particular target in mind;

all

target-dependencies are

represented in the GUI data provided by the target to the controller.

Group 1

Panel 1

Element 1 Element 2

Element 3 Element 4

GUI element 1 and 2

belong to group 1.

Group 1 is the parent of

these two GUI elements

GUI element 3 and 4 are

"free", and exist within

the panel itself

Panel 1 is the parent of

Group 1, and GUI

elements 3 and 4.

Group 1

Panel 1

Element 1 Element 2

Element 3 Element 4

GUI element 1 and 2

belong to group 1.

Group 1 is the parent of

these two GUI elements

GUI element 3 and 4 are

"free", and exist within

the panel itself

Panel 1 is the parent of

Group 1, and GUI

elements 3 and 4.

TA Document 2001001, May 8, 2001 AV/C Panel Subunit Specification 1.1

It should be emphasized that the controller usually does not understand what happens as a result of issuing

a user input control message to the target. So in addition to well-known functionalities, it is possible to

handle new functionality on the target device which cannot be assumed in advance.

The direct mode uses an asymmetric data transfer (ADT) model for the controller-target interaction. With

this ADT model, the control data from controller to target is transferred using AV/C commands, while the

GUI data from target to controller is transferred using an Asynchronous Connection.

The following diagram illustrates a typical interaction sequence between a controller and a target in the

direct mode:

Figure 4.7 – Detailed Interactions between Controller and Panel subunit

When the controller starts working with the panel subunit, the controller will first check the availability of a

source plug of the panel subunit and reserve the source plug using GUI UPDATE control command with

open subfunction. If the command is accepted, the controller gets the ownership of the source plug.

Then the controller makes the internal connection between the target unit and the panel subunit by using

CONNECT command specified in reference [R1].

After that, the controller makes an asynchronous connection between the controller unit and the unit that

contains the panel subunit, using ALLOCATE ATTACH subfunction in ASYNCHRONOUS

CONNECTION command, etc. specified in the reference [R3]. If all connections succeed, the data path

between the controller and the panel subunit is established.

Note that the controller may use different way to establish the asynchronous connection if the other ways

are specified. However the connection between the controller and the panel subunit shall be established

response

PUSH GUI DATA

GUI data

(Asynchronous Connection)

ALLOCATE ATTACH

response

The controller constructs

the GUI display and begins

interacting with the user

The controller establishes

Asynchronous connection

response

GUI UPDATE(start)

GUI data

(Asynchronous Connection)

USER ACTION

response

GUI data has

been changed

The controller gets the

modified GUI elements

and updates the display

...

DETACH RELEASE

response

When controller completes

tasks with the target, it

cancels any notification from

target, and disconnects AC.

response

GUI UPDATE (close)

Controller

Target

Panel Subunit

response

GUI UPDATE(open)

response

GUI UPDATE (stop)

response

CONNECT

response

PUSH GUI DATA

GUI data

(Asynchronous Connection)

ALLOCATE ATTACH

response

The controller constructs

the GUI display and begins

interacting with the user

The controller establishes

Asynchronous connection

response

GUI UPDATE(start)

GUI data

(Asynchronous Connection)

USER ACTION

response

GUI data has

been changed

The controller gets the

modified GUI elements

and updates the display

...

DETACH RELEASE

response

When controller completes

tasks with the target, it

cancels any notification from

target, and disconnects AC.

response

GUI UPDATE (close)

Controller

Target

Panel Subunit

response

GUI UPDATE(open)

response

GUI UPDATE (stop)

response

CONNECT

AV/C Panel Subunit Specification 1.1 TA Document 2001001, May 8, 2001

after GUI UPDATE with open subfunction is accepted and before the controller issues GUI UPDATE with

start subfunction.

The communication process starts with the controller sending the GUI UPDATE command with “start”

subfunction to the panel subunit to interact with the panel subunit. This command also indicates the

notification scope: a full or partial panel. The notification scope can be changed any time by issuing a new

GUI UPDATE command with “change” subfunction.

The PUSH GUI DATA command is a request for some specific GUI element(s). The target sends the

requested GUI information over the asynchronous connection. The controller starts accessing some or all of

the GUI data structures (panels, groups or GUI elements). The controller does this by first sending the GUI

request, i.e. PUSH GUI DATA command, to get the root panel, i.e. the first menu of the target, or some

GUI elements with the root panel. After getting the GUI data, the controller renders the GUI elements on

the display screen, and begins interacting with the user. Thereafter, the controller may:

update the GUI representation that is being displayed to the user by a controller implementation-

dependent mechanism;

2) ask the target for more GUI elements using the PUSH GUI DATA; or

send user action information to the target according to the contents of the GUI element and the

user input.

At any time after a controller has requested notification from the target, using the start subfunction of the

GUI UPDATE command, and before the controller cancels the notification, using the stop subfunction of

the GUI UPDATE command, the target may indicate the changed GUI element(s) to the controller. For

example, indicating that some aspect of the target’s internal state which is relevant to the user has changed.

The indication will be done by the target spontaneously sending GUI elements to the controller over the

asynchronous connection and will provide the controller with information about which parts of the target’s

GUI presentation have changed.

When the user operates the GUI element, the controller sends the user action by USER ACTION control

command to the panel subunit, and the USER ACTION control command is generally accepted. If one or

more GUI elements have been changed as a result of the user action, the panel subunit sends the changed

GUI element(s) to the controller over the asynchronous connection.

For example, a GUI button pressed by the user may attempt to place a target VCR into a “rewinding” mode

and the target may wish to indicate the success (or failure) of the command by sending a TEXT element

with an appropriate string value over asynchronous connection.

In this manner the user and the target device communicate with each other through a sequence of

commands and responses sent between the controller and the target, guided by the GUI data the controller

obtained from the target panel subunit.

When the controller stops interacting with a target, it sends a GUI UPDATE command with “stop”

subfunction to that target; this cancels ALL outstanding notification requests for that controller. The target

shall thereafter not send any changed GUI data to that controller and the controller shall not send any other

USER ACTION commands to that target. The controller may restart the interaction by sending another

GUI UPDATE command with “start” subfunction to the same target.

If there are no more interactions between the controller and the target and after “stop” subfunction is

accepted, the AC-CTR can issue DETACH_RELEASE subfunction in ASYNCHRONOUS

CONNECTION command to the target to close the asynchronous connection.

After the asynchronous connection between the controller and the target is broken, the controller sends a

GUI UPDATE command with “close” subfunction to that target; this cancels the controller’s ownership for

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