Patent Publication Number: US-8996732-B2

Title: Methods and devices for CEC block termination

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application also claims the benefit of U.S. Provisional Patent Application No. 61/056,432, filed on May 27, 2008, incorporated herein by reference. 
    
    
     BACKGROUND 
     The HDMI™ (High-Definition Multimedia Interface) standard, of the HDMI consortium, is a digital interface for audio and video signals. HDMI-CEC refers to an HDMI device that supports CEC (Consumer Electronics Control). HDMI-CEC devices enable a user to manage a plurality of sources connected via HDMI with no special programming needed and to run operations such as ‘one touch play’. Using HDMI-CEC, the user may, for example, use one remote control to turn on the TV, DVD, and receiver at the same time, and to adjust the system volume using one button. 
     The HDMI-CEC protocol uses a one-wire shared bus that includes automatic mechanisms for logical address allocation based on product type, arbitration, retransmission, broadcasting, and switching control. Operation code (opcode) supports both device specific and general features. CEC devices have both physical and logical addresses. Normally, upon hot-plugging, each CEC source device obtains a physical address by reading the EDID of the display device to which it is attached. 
     In some embodiments, an HDMI-CEC message, shortly referred to as “CEC message”, includes the following CEC blocks: a special start ‘bit’, a header block containing source and destination addresses, a first data block containing optional opcode, and a second data block containing optional operands specific to the opcode. The maximum CEC message size (header block plus opcode block plus operand blocks) is 16*10 bits. Each CEC block includes 8 bits of data, one End-Of-Message (EOM) bit, and one acknowledge (ACK) bit transmitted by the receiver. A CEC message includes a series of CEC blocks wherein only the EOM bit of the last block in the message is on. Each CEC message starts with a block having 4 bits of source address (also referred to as nibble), 4 bits of destination address, an EOM bit, and an ACK bit. A polling message includes the same source and destination addresses with the EOM bit on. 
     CEC includes an option for customized commands. This enables different vendors to create CEC based networks between products of the specific vendor. Examples of such modified CEC base networks include: Anynet (Samsung), Aquos Link (Sharp), BRAVIA Theatre Sync (Sony), Regza Link (Toshiba), RIHD (Onkyo), Simplink (LG), Viera Link/EZ-Sync (Panasonic/JVC), Easylink (Philips) and NetCommand for HDMI (Mitsubishi). 
     BRIEF SUMMARY 
     In one embodiment, a manipulating switch including: a first HDMI-CEC port to receive a CEC block including source and destination CEC logical addresses according to the initiator&#39;s HDMI-CEC network view; logic to acknowledge the CEC block, if it is not a broadcast block, and to modify the source and destination CEC logical addresses according to the follower&#39;s HDMI-CEC network view; and a second HDMI-CEC port to forward the modified CEC block to the follower. 
     In one embodiment, an HDMI-CEC device storing a first CEC logical address matching a first HDMI-CEC cluster tree of a first HDMI-CEC display device, whereby the HDMI-CEC device is also associated with a second HDMI-CEC cluster tree of a second HDMI-CEC display device through a manipulating switch; in the network view of the second HDMI-CEC display device, the manipulating switch assigns to the HDMI-CEC device a second CEC logical address that is different from the first CEC logical address; wherein the manipulating switch is capable of receiving a CEC block, acknowledging the CEC block, modifying the CEC block, and forwarding the modified CEC block to the HDMI-CEC device. 
     In one embodiment, a method including: receiving a CEC block through a first HDMI-CEC port and acknowledging the CEC block; modifying one or more bits in the received CEC block; and sending the modified CEC block through at least a second HDMI-CEC port. 
     In one embodiment, a method including: receiving a CEC block including a destination logical address matching the initiator&#39;s HDMI-CEC network view; acknowledging the CEC block; and modifying the destination logical address to match the follower&#39;s HDMI-CEC network view. 
     Implementations of the disclosed embodiments involve performing or completing selected tasks or steps manually, semi-automatically, fully automatically, and/or a combination thereof. Moreover, depending upon actual instrumentation and/or equipment used for implementing the disclosed embodiments, several embodiments could be achieved by hardware, by software, by firmware, or a combination thereof. In particular, with hardware, embodiments of the invention could exist by variations in the physical structure. Additionally, or alternatively, with software, selected functions of the invention could be performed by a data processor, such as a computing platform, executing a software instructions or protocols using any suitable computer operating system. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the embodiments. In the drawings: 
       The embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. No attempt is made to show structural details of the embodiments in more detail than is necessary for a fundamental understanding of the embodiments. In the drawings: 
         FIG. 1A  illustrates a multi display network in accordance with one embodiment of the invention; 
         FIG. 1B  illustrates a multi port display device in accordance with one embodiment of the invention; 
         FIG. 1C  illustrates a manipulating switch inside a display device in accordance with one embodiment of the invention; 
         FIG. 2  illustrates a multi port display device in accordance with one embodiment of the invention; 
         FIG. 3  illustrates a multi stream network in accordance with one embodiment of the invention; 
         FIG. 4  illustrates a multi stream network in accordance with one embodiment of the invention; 
         FIG. 5A  illustrates a daisy chain in accordance with one embodiment of the invention; 
         FIG. 5B  illustrates a multi stream manipulating switch inside a source device in accordance with one embodiment of the invention; 
         FIG. 5C  illustrates a multi stream manipulating switch inside a source device in accordance with one embodiment of the invention; 
         FIG. 5D  illustrates a multi stream network in accordance with one embodiment of the invention; 
         FIG. 5E  illustrates a multi stream manipulating switch inside a source device in accordance with one embodiment of the invention; 
         FIGS. 6A-C  illustrate HDMI-CEC network views in accordance with one embodiment of the invention; 
         FIG. 7  illustrates a multi display network in accordance with one embodiment of the invention; 
         FIG. 8  illustrates a multi display network in accordance with one embodiment of the invention; 
         FIG. 9  illustrates a multi display network in accordance with one embodiment of the invention; 
         FIG. 10  illustrates a manipulating switch in accordance with one embodiment of the invention; 
         FIGS. 11A-11B  illustrate symmetric communication channels in accordance with one embodiment of the invention; 
         FIG. 12  is a flow diagram of one method in accordance with one embodiment of the invention; 
         FIG. 13  is a flow diagram of a routing method in accordance with one embodiment of the invention; 
         FIG. 14  is a flow diagram of an emulating method in accordance with one embodiment of the invention; 
         FIG. 15  is a flow diagram of a menu creation method in accordance with one embodiment of the invention; 
         FIG. 16  is a flow diagram of a menu creation method in accordance with one embodiment of the invention; 
         FIG. 17  is a flow diagram of a propagation control method in accordance with one embodiment of the invention; 
         FIG. 18  is a flow diagram of a propagation control method in accordance with one embodiment of the invention; 
         FIG. 19  is a flow diagram of a CEC on the fly modification method in accordance with one embodiment of the invention; 
         FIG. 20  is a flow diagram of a CEC block termination method in accordance with one embodiment of the invention; 
         FIG. 21  is a flow diagram of a method in accordance with one embodiment of the invention; 
         FIG. 22  is a flow diagram of an addresses allocation method in accordance with one embodiment of the invention; 
         FIG. 23  is a flow diagram of a logical addresses acquiring method in accordance with one embodiment of the invention; 
         FIG. 24  is a flow diagram of a logical addresses acquiring method in accordance with one embodiment of the invention; and 
         FIG. 25  is a flow diagram of a physical addresses assignment method in accordance with one embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, numerous specific details are set forth. However, the embodiments of the invention may be practiced without these specific details. In other instances, well-known hardware, software, materials, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. In this description, references to “one embodiment” or “an embodiment” mean that the feature being referred to is included in at least one embodiment of the invention. Moreover, separate references to “one embodiment” in this description do not necessarily refer to the same embodiment. Illustrated embodiments are not mutually exclusive, unless so stated and except as will be readily apparent to those of ordinary skill in the art. Thus, the invention may include any variety of combinations and/or integrations of the embodiments described herein. Also herein, flow diagrams illustrate non-limiting embodiment examples of the methods, and block diagrams illustrate non-limiting embodiment examples of the devices. Some flow diagrams operations are described with reference to the embodiments illustrated by the block diagrams. However, the methods of the flow diagrams could be performed by embodiments of the invention other than those discussed with reference to the block diagrams, and embodiments discussed with reference to the block diagrams could perform operations different from those discussed with reference to the flow diagrams. Moreover, although the flow diagrams may depict serial operations, certain embodiments could perform certain operations in parallel and/or in different orders from those depicted. Moreover, the use of repeated reference numerals and/or letters in the text and/or drawings is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     In the following description, numerous specific details are set forth. However, the embodiments of the invention may be practiced without these specific details. In other instances, well-known hardware, software, materials, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. In this description, references to “one embodiment” or “an embodiment” mean that the feature being referred to is included in at least one embodiment of the invention. Moreover, separate references to “one embodiment” in this description do not necessarily refer to the same embodiment. Illustrated embodiments are not mutually exclusive, unless so stated and except as will be readily apparent to those of ordinary skill in the art. Thus, the invention may include any variety of combinations and/or integrations of the embodiments described herein. Also herein, flow diagrams illustrate non-limiting embodiment examples of the methods, and block diagrams illustrate non-limiting embodiment examples of the devices. Some operations in the flow diagrams may be described with reference to the embodiments illustrated by the block diagrams. However, the methods of the flow diagrams could be performed by embodiments of the invention other than those discussed with reference to the block diagrams, and embodiments discussed with reference to the block diagrams could perform operations different from those discussed with reference to the flow diagrams. Moreover, although the flow diagrams may depict serial operations, certain embodiments could perform certain operations in parallel and/or in different orders from those depicted. Moreover, the use of repeated reference numerals and/or letters in the text and/or drawings is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     DVI™ (Digital Visual Interface) is a video interface standard designed by the Digital Display Working Group consortium. HDMI™ (High-Definition Multimedia Interface) is a digital interface for audio and video signals designed by the HDMI consortium. DisplayPort™ is a digital display interface standard put forth by the Video Electronics Standards Association (VESA)™. 
     Conventional CEC networks assume a network topology including only one display device. A display device may be any kind of video display, television, or projector. Some of the following embodiments discuss the operation of novel methods and systems for utilizing HDMI-CEC in a network including more than one display device and novel methods and systems for multi-display networks supporting HDMI-CEC. The embodiments may operate with standard HDMI-CEC devices and/or with partially compatible devices. 
     An HDMI-CEC input port is associated with an “HDMI-CEC cluster tree” which includes all the upstream devices having HDMI physical paths to that HDMI-CEC input port. Herein, the upstream direction is from a sink device to a source device, and the downstream direction is from a source device to a sink device. 
     The term “HDMI-CEC network view” includes the network topology and the linkage between HDMI physical addresses and CEC logical addresses as exposed to a device through the CEC &lt;report physical address&gt; messages that it receives. It is to be understood that the “HDMI-CEC cluster tree” represents the actual physical topology while the “HDMI-CEC network view” may be manipulated, for example, by a manipulating switch as described below. The HDMI-CEC network view of device ‘X’ enables device ‘X’ to communicate with the various devices available in its HDMI-CEC network view. 
     In some of the embodiments, “manipulating switch” denotes a component comprising at least one input port supporting HDMI-CEC and at least two output ports supporting HDMI-CEC transactions. A manipulating switch may also be any component comprising at least one input and at least two outputs which capable of delivering HDMI-CEC data. A manipulating switch may utilize any physical transmission that can be converted to HDMI-CEC. Optionally, the manipulating switch may be located within or integrated with one of the HDMI-CEC source devices. Optionally, the manipulating switch may be located within or integrated with one of the HDMI-CEC display devices. The manipulating switch may be implemented as a single component. Alternatively, the manipulating switch may be implemented as two or more interconnected components, optionally forming a cluster and/or network, whereby the described functionality of the manipulating switch may refer to the functionality accomplished by a part or the whole of the cluster and/or network.  FIG. 3  illustrates a manipulating switch  41  representing two or more components forming the manipulating switch functionality together. 
     It is to be understood that “HDMI-CEC cluster tree” may refer to an entire network or refer just to a sub-network. Referring to  FIG. 1A  as an example, in one case, source devices  13 - 17  form a first HDMI-CEC cluster tree coupled to display device  21 , and the same source devices  13 - 17  form a second HDMI-CEC cluster tree coupled to display device  22 . In another example, display device  21  and source devices  13 - 17  form a first HDMI-CEC cluster tree, and display device  22  and source devices  13 - 17  form a second HDMI-CEC cluster tree. The manipulating switch  23  may or may not be regarded as included in one or more of the HDMI-CEC cluster trees. 
     Multiple Display Network Supporting HDMI-CEC 
     In prior art HDMI-CEC devices every CEC message is received by all devices connected to the HDMI-CEC cluster tree and only one output port may be connected to the HDMI-CEC cluster tree. 
       FIG. 1A  illustrates one embodiment of a manipulating switch  23  that includes logic that enables a plurality of HDMI-CEC display devices ( 21 ,  22 ) to control an HDMI-CEC cluster tree, comprised of standard HDMI-CEC sources ( 13 ,  14 ,  16 ,  17 ) and standard HDMI-CEC switch  15 . 
     The manipulating switch  23  dynamically manipulates the HDMI-CEC network views, such that when none of the source devices is active, each display device may control all source devices. And when a first display device communicates with a first source device using HDMI-CEC, the second display device can still communicate with the other source device using HDMI-CEC. For example, when none of the source devices is active, display device  21  may control, through its CEC bus, source devices  13 ,  14 ,  16 , and  17  and switches  23  and  15 . Display device  22  may also control, through its CEC bus, the same source devices  13 ,  14 ,  16 , and  17  and switches  23  and  15 . When display device  21  activates source device  16 , the manipulating switch  23  manipulates the HDMI-CEC network view of display device  22  to reflect only source devices  13  and  14 . Source device  17  is also erased from the HDMI-CEC network view of display device  22  because it is connected though HDMI link  23   c  which is already used by source device  16 . 
       FIG. 12  is a flow diagram illustrating one method comprising the following steps: In step  120 , manipulating HDMI-CEC messages transmitted over a network comprising at least two HDMI-CEC display devices with their associated at least two HDMI-CEC cluster trees that at least partially overlap. And in step  121 , enabling each of the HDMI-CEC display devices to communicate using HDMI-CEC with its associated HDMI-CEC cluster tree according to its current HDMI-CEC network view. 
       FIGS. 1B-1C  illustrate one embodiment wherein the manipulating switch  1   c   1  is located within the display device  1   b   1 . The manipulating switch  1   c   1  includes logic that enables a plurality of HDMI-CEC display devices ( 1   b   1 ,  1   b   3 ) to control an HDMI-CEC cluster tree, comprised of standard HDMI-CEC sources ( 13 ,  14 ). The embodiment illustrated by  FIG. 1B  enables a user to chain two or more display devices such that when none of the source devices is active, each display device may control all source devices, and when a first display device communicates with a first source device using HDMI-CEC, the second display device can still communicate with the second source device using HDMI-CEC. 
       FIG. 2  illustrates one embodiment of a display device with a manipulating switch  12  that includes logic for controlling overlapping or partially overlapping HDMI-CEC networks. By using the manipulating switch  12 , and assuming that the CEC buses of  11   a  and  11   b  are not physically connected, both HDMI-CEC ports ( 11   a ,  11   b ) may control the HDMI-CEC sources ( 13 ,  14 ,  16 ,  17 ). The HDMI-CEC ports ( 11   a ,  11   b ) may be coupled to a standard HDMI-CEC display device  11  as illustrated. In the specific non-limiting example of  FIG. 2 , the manipulating switch  12  resides within a display box  10  (such as a television, a monitor or a projector), but it is to be understood that the manipulating switch  12  may reside within any other display device, source device, or as a stand-alone device. The manipulating switch  12  selects and manipulates the data to be transmitted over the different HDMI-CEC networks connected to HDMI-CEC ports  11   a  and  11   b.    
       FIG. 13  is a flow diagram illustrating one method for enabling picture-in-picture in a display device comprising two HDMI-CEC input ports, each of the HDMI-CEC input ports associated with an HDMI-CEC cluster tree, and the HDMI-CEC cluster trees at least partially overlapping, the method comprising the following steps: In step  130 , defining an HDMI-CEC network view for each HDMI-CEC input port. In step  131 , controlling the HDMI-CEC messages transmitted between each HDMI-CEC input port of the HDMI-CEC display device and its HDMI-CEC cluster tree. In step  132 , controlling the HDMI-CEC messages transmitted between the HDMI-CEC cluster trees. And in step  133 , enabling selecting which of the HDMI-CEC source devices to route to which of the HDMI-CEC input ports using HDMI-CEC messages. 
     Referring again to  FIG. 2 , the manipulating switch  12  includes logic that enables it to communicate with source devices  13  and  14 , and with source devices  16  and  17  through switch  15 , using HDMI-CEC, and still output one or more pictures through ports  11   a  and  11   b . This capability enables the display device  11  to have, for example, a picture-in-picture feature, while it is possible to control each picture&#39;s source through the HDMI-CEC network view. It may also be possible to operate all the sources ( 13 ,  14 ,  16 ,  17 ), using the display&#39;s remote control, through standard HDMI-CEC, while having the picture-in-picture feature. 
     In one embodiment, the physical addresses, and optionally the logical addresses, of the HDMI-CEC network are approximately duplicated by the manipulating switch  12 , such that the display device  11  is able to control sources ( 13 ,  14 ,  16 , and  17 ) either through HDMI-CEC port  11   a  or through HDMI-CEC port  11   b.    
     In one embodiment, the manipulating switch  12  transmits some data between the two HDMI-CEC networks. It is possible to control what data will be transferred between the HDMI-CEC cluster trees and when. 
     Operating the Video Network 
     Prior art HDMI-CEC networks having one display device enable the user to: (i) operate the HDMI-CEC cluster tree using a display device, optionally utilizing the set-stream-path message, and (ii) operate the HDMI-CEC cluster tree using a source device, optionally utilizing the one touch play feature. 
     In one embodiment, at least one source device is connected through at least one manipulating switch to at least two display devices, and a user operates the HDMI-CEC network through a display device utilizing the set-stream-path message. The display device is able to operate the required source device using the standard set-stream-path message because the manipulating switch makes each display device believe it is connected to a standard HDMI-CEC network having one display device. 
     In one embodiment, at least one source device is connected through at least one manipulating switch to at least two display devices, and a user operates the HDMI-CEC network through a source device utilizing the one touch play feature. In this embodiment, when a source device activates a display device, for example, by utilizing the ‘one-touch play’ CEC feature, for example as described in HDMI spec 1.3 paragraph “CEC 13.1 One Touch Play”, the manipulating switch should select which of the available display devices to connect with the source device. The logic for selecting the display device to be connected to the source device may be predefined, dynamically selected, and/or manually selected. 
     For example, the display device on which the content is to be displayed may be selected according to one of the following non-limiting examples: displaying the content on a display device that is defined as the primary display device; displaying the content on a display device that is already active; or displaying the content on a display device that is not active. 
     Referring again to  FIG. 1A  as an example, if source  16  is operating a ‘one-touch play’ while display device  21  plays content from source device  13 , manipulating switch  23  may connect source device  16 , instead of source device  13 , to display device  21 ; or connect source device  16  to display device  22 ; or display a menu on display device  21  and/or on display device  22  in order to enable the user to select the desired display device; or connect source device  16  to the display device it was last connected to; or operate according to any other reasonable logic. 
     In one embodiment, when the user tries to operate the HDMI-CEC cluster tree from the source device, optionally using the one touch play feature, the manipulating switch takes over and the HDMI-CEC cluster tree is operated from the switch as discussed in the next paragraphs. In other words, operation from a source device may cause operation from the manipulating switch. 
     In one embodiment, at least one source device is connected through at least one manipulating switch to at least two display devices, and a user operates the network, which supports HDMI-CEC, through a manipulating switch that performs one or more of the following operations: (i) communicating with the various HDMI devices using the HDMI-CEC protocol, including spoofing when needed and as explained below, (ii) creating a control menu, which includes the display devices, and (iii) sending the control menu to at least one of the display devices for displaying. 
     Optionally, the user operates the control menu, created by the manipulating switch, through the remote control of the manipulating switch. Alternatively, the user operates the control menu, created by the manipulating switch, through any other appropriate means such as a multifunctional remote control communicating with the manipulating switch, or though the remote control of one of the display devices, wherein the display device forwards the user&#39;s selections to the manipulating switch. The display device may forward the user&#39;s selections to the manipulating switch directly or following a manipulation by the manipulating switch. One example of such a manipulation is when the manipulating switch emulates a source device that displays its menu on the display device using CEC available mechanisms for displaying menu and retrieves remote control actions. Examples of such CEC mechanisms are described in HDMI specification 1.3 paragraph “CEC 13.12 Device Menu Control” and include messages such as &lt;User Control Pressed&gt;, &lt;User Control Released&gt;, &lt;Menu Request&gt;, or &lt;Menu Status&gt;. 
     In one embodiment, in order to operate the HDMI-CEC cluster tree through the manipulating switch, the manipulating switch supplies the user with the devices available in the manipulated HDMI-CEC cluster tree (i.e. not bounded by the standard CEC rules). 
       FIG. 15  is a flow diagram illustrating one method for operating a network comprising at least two HDMI-CEC display devices with their associated at least two HDMI-CEC cluster trees that at least partially overlap, comprising the following steps: In step  150 , communicating with the various HDMI-CEC cluster trees using HDMI-CEC. In step  151 , creating a control menu which comprises the HDMI-CEC display devices. In step  152 , sending the control menu to at least one of the HDMI-CEC display devices for display. And in step  153 , operating the control menu according to a user&#39;s selection. 
       FIG. 16  is a flow diagram illustrating one method for operating a network comprising at least two HDMI-CEC display devices with their associated at least two HDMI-CEC cluster trees that at least partially overlap, comprising: In step  160 , communicating with the various HDMI-CEC cluster trees using HDMI-CEC. In step  161 , creating a control menu for each of the HDMI-CEC display devices. In step  162 , sending the control menus to the HDMI-CEC display devices for display. In optional step  163 , operating each control menu by a remote control of the HDMI-CEC display device on which it is displayed. And in optional step  164 , forwarding the user&#39;s selections from the HDMI-CEC display device to a manipulating switch. 
     Multi-Stream Channel Supporting CEC 
     Utilizing a Multi-Stream Channel Within an HDMI-CEC cluster tree. 
     Standard HDMI interface supports only one stream. A channel that is capable of transferring more than one HDMI stream is referred to herein as a multi-stream channel supporting HDMI-CEC. In some embodiments, the multi-stream channel supporting HDMI-CEC may be coupled to two or more HDMI output ports and therefore is somehow similar to a device having multiple HDMI inputs and multiple HDMI outputs. 
     A multi-stream manipulating switch refers to a switch that supports at least one multi stream channel. In one embodiment, the multi-stream manipulating switch is capable of manipulating at least some of the HDMI and CEC control transactions. A source device supporting a multi-stream daisy chain is referred to herein as a source device supporting multi-stream. 
     In one embodiment, one or more multi-stream channel supporting HDMI-CEC are embedded within an HDMI-CEC network, or within a network that is compatible or partially compatible with HDMI-CEC. As a result of using the multi-stream channel, it is possible to operate more than one source device connected to the HDMI-CEC cluster tree spanned by the multi-stream channel. Moreover, the system has to manipulate the HDMI-CEC cluster trees connected to the different display devices in order to be able to operate the source devices using CEC messages. 
       FIG. 3  illustrates one embodiment of a multi-display network supporting HDMI-CEC with a multi-stream channel  41   c . The display devices ( 21 ,  22 ) are connected to multi-stream manipulating switch  41  that is connected to multi-stream manipulating switch  42  through a multi-stream channel supporting HDMI-CEC  41   c . In the illustrated embodiment, manipulating switch  41  is implemented as two or more interconnected components, optionally forming a cluster and/or network, whereby the described functionality of the manipulating switch  41  may refer to the functionality accomplished by a part or the whole of the cluster and/or network. In one embodiment, after source device  16  starts transmitting to display device  21 , display device  22  may only access devices  13 ,  14 , and  17 . But the available bandwidth of the multi-stream channel supporting HDMI-CEC  41   c  decreases and therefore the multi-stream manipulating switch  41  has to make sure that future transmissions from source device  17  will be limited to the available bandwidth of  41   c . The throughput from source device  17  may be limited, for example, by implementing the following method: 
     Multi-stream manipulating switch  42  removes the HPD signal to source device  17 ; 
     Then source device  17  initiates a read EDID transaction; 
     Multi-stream manipulating switch  42  replies the read EDID transaction with a prefetched, manipulated, EDID of display device  22 , such that only video formats that match the available bandwidth of the multi-stream channel  41   c  are exposed to source device  17 . 
       FIG. 4  illustrates an embodiment where display box  30  includes a multi-stream manipulating switch  31  outputting two standard HDMI output signals through ports  11   a  and  11   b  to the display device  11 . Multi-stream manipulating switch  31  communicates with multi-stream manipulating switch  42  through a multi-stream channel supporting HDMI-CEC  31   c . Multi-stream manipulating switch  42  communicates with the source devices ( 16 ,  17 ) through standard HDMI-CEC interface ( 32   a ,  32   b ). When none of the source devices is active, and assuming that the CEC buses of ports  11   a  and  11   b  are not physically connected, the source devices ( 13 ,  14 ,  16 ,  17 ) are visible to the display device  11  in one or two HDMI-CEC network views (because display device  11  has only two HDMI-CEC inputs,  11   a  and  11   b , it cannot have more than two HDMI-CEC network views). 
     After source device  16  is activated through port  11   a , and because channel  31   c  is a multi-stream channel supporting HDMI-CEC, it is still possible to communicate with source device  17  through port  11   b . Therefore, multi-stream manipulating switch  31  manipulates the HDMI-CEC network view such that source devices  13 ,  14 , and  17  appear to be in the HDMI-CEC network view of port  11   b , and therefore HDMI-CEC display device  11  is still able to communicate with one of the remaining source devices ( 13 ,  14 , and  17 ). 
     When initializing the two HDMI-CEC network views of ports  11   a  and  11   b , multi-stream manipulating switch  31  may place the source devices  16  and  17  under the same HDMI-CEC network view or under different HDMI-CEC network views. Optionally, when channel  31   c  is a multi-stream channel supporting HDMI-CEC, the multi-stream manipulating switch  31  may manipulate the HDMI-CEC network views as needed and locate source devices  16  and  17  to be in the HDMI-CEC network view of port  11   a  or in the HDMI-CEC network view of port  11   b.    
     In one embodiment, after source device  16  starts transmitting to port  11   a , source device  17  is manipulated by multi-stream manipulating switch  31  to be in the HDMI-CEC network view of port  11   b . But the available bandwidth of the multi-stream channel supporting HDMI-CEC  31   c  decreases and therefore the multi-stream manipulating switch  31  has to make sure that future transmissions from source device  17  will be limited to the available bandwidth of the multi-stream channel supporting HDMI-CEC  31   c . The throughput from source device  17  may be limited, for example, by implementing the following method: 
     Multi-stream manipulating switch  42  removes and restores the HPD signal to source device  17 , in order to cause source  17  to read the EDID; 
     Then source device  17  initiates a read EDID transaction; and then 
     Multi-stream manipulating switch  42  replies the read EDID transaction with a prefetched, manipulated, EDID of display device  11  such that only video formats that match the available bandwidth of the multi-stream channel supporting HDMI-CEC  31   c  are exposed to source device  17 . For example, assuming link  31   c  is a multi-stream channel supporting HDMI-CEC that is capable of transporting a total throughput of 8 Gbps, which is suitable for transmitting 1080p, 60 Hz, 48 bit per pixel (bpp); If source device  16  transmits 1080p 60 Hz 24 bpp to port  11   a , the multi-stream channel supporting HDMI-CEC  31   c  still has enough bandwidth to transmit another 1080p 60 Hz 24 bpp stream. Assuming display device  11  EDID indicates it can support 1080p 60 Hz 36 bpp, then if source device  17  tries to transmit this kind of video format, the multi-stream channel supporting HDMI-CEC  31   c  will not have enough capacity. Therefore, multi-stream manipulating switch  42  removes and restores the HPD signal to source device  17 , so that source  17  reads the manipulated EDID of display device  11 , such that no other formats requiring higher bandwidth than the available bandwidth seem to be supported by port  11   b.    
     In another example, it is required to ensure in advance that there is enough bandwidth for a predefined number of source devices capable of transmitting over a multi-stream channel supporting HDMI-CEC. In this case, before the first source device starts transmitting, the EDID of the appropriate display device is manipulated such that the total maximum bandwidth consumed by the predefined number of the source devices communicating in parallel through the multi-stream channel supporting HDMI-CEC is supported by the multi-stream channel. For example, if  31   c  is a multi-stream channel supporting HDMI-CEC capable of transmitting a total throughput of 8 Gbps, each of source devices  16  and  17  will be supplied with formats having a throughput that is equal to or lower than 1080p 60 Hz 24 bpp stream. 
     Multi-Stream Daisy Chain Supporting HDMI-CEC. 
       FIG. 5A  illustrates a multi-stream sub network within a multi-display network supporting HDMI-CEC having a multi-stream daisy chain including source devices supporting multi-stream  52 , and  53 , and source device  54 , connected through the multi-stream channels supporting HDMI-CEC  51   a  and  52   a  to the multi-stream manipulating switch  51 , that is connected to display devices  55 ,  56 , and  57 . In this embodiment, the multi-stream manipulating switch  51  and each of the source devices supporting multi-stream ( 52 ,  53 ) have to calculate their upstream residue bandwidth, and then expose only the video formats that match the available bandwidth of the chain&#39;s bottleneck. 
     For example, multi-stream channels supporting HDMI-CEC  51   a  and  52   a  have a maximum throughput of 8 Gbps each. Assuming display device  56  requests from source device supporting multi-stream  52  to start transmitting a 6 Gbps stream over the multi-stream channel supporting HDMI-CEC  51   a , then the multi-stream channel supporting HDMI-CEC  51   a  has a residue bandwidth of 2 Gbps. Therefore, source device supporting multi-stream  52  transmits to source device supporting multi-stream  53  a message informing it that the residue bandwidth is 2 Gbps. In one embodiment, the multi-stream channel supporting HDMI-CEC includes an internal control channel between its nodes. Optionally, device  52  utilizes the internal control channel for transmitting to device  53  the message informing that the residue bandwidth is 2 Gbps. Thereafter, assuming display device  57  requests from source device  54  to start transmitting, then source device supporting multi-stream  53  removes and restores the HPD signal to source device  54 , in order to make it read the EDID of a virtual display device supporting up to 2 Gbps. 
       FIG. 5B  illustrates one embodiment of a source device supporting multi-stream  53 , including: (i) an HDMI input port  53   a , (ii) a data source  58   a , and (iii) a multi-stream manipulating switch  58   b  having two HDMI inputs ports and one multi-stream channel supporting HDMI-CEC  52   a  output. Optionally, the source device supporting multi-stream  53  is capable of utilizing the multi-stream channel supporting HDMI-CEC  52   a  for data received from the data source  58   a , or data received from the HDMI input port  53   a , or for data received from both inputs. 
       FIG. 5C  illustrates one embodiment of a source device supporting multi-stream  52 , including: (i) an input for receiving a multi-stream channel supporting HDMI-CEC  52   a , (ii) a data source  58   c , and (iii) a multi-stream manipulating switch  58   d  having one HDMI stream input, one multi-stream channel supporting HDMI-CEC input, and one multi-stream channel supporting HDMI-CEC  51   a  output. Optionally, the source device supporting multi-stream  52  is capable of utilizing the multi-stream channel supporting HDMI-CEC  51   a  for data received from the data source  58   c , or data received from the multi-stream channel supporting HDMI-CEC  52   a , or for data received from both inputs. 
       FIGS. 5D-5E  illustrate one embodiment wherein the multi-stream manipulating switch  552   a  is located within a display device  552 . The multi-stream manipulating switch  552   a  includes logic which enables a plurality of HDMI-CEC display devices ( 552 ,  56 ) to control an HDMI-CEC cluster tree, comprising a standard HDMI-CEC source  54  and a source device supporting multi-stream  53 . The embodiment illustrated by  FIG. 5D  enables a user to connect a chain of source devices (linked using at least one multi-stream channel supporting HDMI-CEC) to a chain of display devices, such that when none of the source devices is active, each display device may control all of the source devices, and when a first display device communicates with a first source device using HDMI-CEC, a second display device can still communicate with the other source devices using HDMI-CEC. 
     Methods for Implementing a Multi-Stream Link. 
     A multi-stream manipulating switch may be connected to a multi-stream channel supporting CEC. The multi-stream channel supporting HDMI-CEC may be implemented using any appropriate technique, as long as the transmitted streams are HDMI-CEC compatible. A multi-stream channel supporting HDMI-CEC may be created using solutions for transmitting HDMI-CEC signals over media such as twisted-pair cables, coax cables, optical fibers, and/or implemented using a wireless solution. 
     Some examples of methods and systems suitable for HDMI-CEC compatible transmissions over a twisted pair cable are available in U.S. patent application Ser. No. 11/703,080, filed on Feb. 7, 2007, which is incorporated herein by reference in its entirety for all that it teaches without exclusion of any part thereof. 
     Some examples of methods and systems suitable for HDMI-CEC compatible transmissions over optical fibers are available in US patent application publication number US20070233906, which is incorporated herein by reference in its entirety for all that it teaches without exclusion of any part thereof. 
     Some examples of methods and systems suitable for HDMI-CEC compatible transmissions through wireless communication are available in PCT patent application publication number WO/2006/101801, which is incorporated herein by reference in its entirety for all that it teaches without exclusion of any part thereof. 
     Examples of Basic CEC Manipulation Functions 
     In one embodiment, the manipulating switch utilizes one or more of the following four CEC manipulation functions. 
     1) CEC Propagation Control. 
     The CEC propagation control function enables the manipulating switch to receive a CEC block which was initiated by a certain device; and pass or intercept the received CEC block to a certain device(s), optionally on the fly, and without modifying the received block. For example, the manipulating switch may divide the HDMI-CEC cluster tree into multiple HDMI-CEC cluster trees and may control the propagation of the CEC blocks between the multiple HDMI-CEC cluster trees; the multiple HDMI-CEC cluster trees may partially overlap. 
     Referring to  FIG. 6A , assume that manipulating switch  64  controls two HDMI-CEC cluster trees. The first HDMI-CEC cluster tree includes source devices  66  and  67  and display device  62 . The second HDMI-CEC cluster tree includes source devices  65 ,  66  and  67  and display device  61 . Utilizing the CEC propagation control function, the manipulating switch  64  controls the propagation of CEC blocks within each of the HDMI-CEC cluster trees and the propagation of CEC blocks between the various HDMI-CEC cluster trees. This means that the manipulating switch may forward certain CEC blocks to some source or display devices and not forward the certain CEC blocks to other source or display devices it is connected to. 
       FIG. 17  is a flow diagram illustrating one method comprising the following steps: In step  170 , receiving a CEC block which was initiated by a first HDMI-CEC device. In step  171 , passing the received CEC block to a second HDMI-CEC device. And in step  172 , preventing a third HDMI-CEC device from receiving the CEC block 
       FIG. 18  is a flow diagram illustrating one method comprising the following steps: In step  180 , dividing a plurality of devices into at least a first HDMI-CEC cluster tree coupled to a first display device, and a second HDMI-CEC cluster tree coupled to a second display device, wherein the HDMI-CEC cluster trees partially overlap. In step  181 , receiving a first CEC block which was initiated by the first HDMI-CEC cluster tree. In step  182 , passing the first CEC block to the first display device not passing the first CEC block to the second display device. 
     2) CEC on the Fly Modification. 
     The CEC on the fly modification function enables the manipulating switch to: (i) receive a CEC block which was initiated by a certain device, (ii) modify one or more bits in the received CEC block, optionally on the fly, and (iii) supply the modified CEC block to a certain device(s). 
     For example, a source device is associated with two HDMI-CEC network views through a manipulating switch, and the source device holds different logical addresses for each HDMI-CEC network view. When a display device, associated with the first HDMI-CEC network view, transmits a CEC message to the source device, that stores a logical address matching the second HDMI-CEC network view, the manipulating switch may replace the CEC destination address with the address matching the second HDMI-CEC network view, such that the source device will identify the CEC message as addressed to it. When, or immediately after, the manipulating switch receives the CEC block containing the four bits of source address and the four bits of destination address, it can determine whether the block was correctly or incorrectly modified. If the block was incorrectly modified, the manipulating switch drops the CEC message, optionally by changing one or more of the address bits or using a &lt;feature abort&gt; message. On the fly modification may also be applied to downstream CEC messages (e.g. from the source device to the display device). In this case, the source device transmits a CEC message using the logical addresses it stores. Then, the manipulating switch may modify the source and/or destination addresses according to addresses matching the recipient&#39;s HDMI-CEC network view. 
     As explained in the HDMI spec 1.3, a transaction on a CEC line involves an initiator and one or more followers. The initiator is responsible for sending the message structure and the data (sometimes both of them referred to herein as data). The follower is the recipient of the data and is responsible for setting any acknowledgement bits. 
       FIG. 19  is a flow diagram illustrating one method comprising the following steps: 
     In step  190 , receiving a CEC message from a first HDMI-CEC port, the CEC message comprising data according to the initiator&#39;s HDMI-CEC network view. In step  191 , modifying the CEC data, approximately on the fly, to match the follower&#39;s HDMI-CEC network view. Optionally, the data is selected from the group of CEC source logical address, or CEC destination logical address, or CEC source logical address and CEC destination logical address. And in step  192 , transmitting the modified CEC message through a second HDMI-CEC port. 
     3) CEC Block Termination. 
     The CEC block termination function enables the manipulating switch to receive a CEC block which was initiated by a certain device; optionally acknowledge (ACK) the block; modify the received block; and supply the modified blocks to a certain device(s). Optionally, a few blocks or all the blocks comprising the CEC may be partially or completely modified. Alternatively, only a section of the block may be modified, for example, only the header containing the logical addresses may be modified. 
     In one embodiment, although the manipulating switch modifies the received block, the source address still matches the source address of the original initiator of the block and not the source address of the manipulating switch. 
     In one embodiment, a transmission is stopped using CEC Line Error Handling, such as defined in HDMI spec 1.3 paragraph CEC 7.4. CEC line error handling enables a device acting as follower to notify all other devices (primarily the initiator) that a potential error has occurred, where an error is defined as a period between falling edges that is shorter than a minimum data bit period. 
       FIG. 20  is a flow diagram illustrating one method comprising the following steps: In step  200 , receiving a CEC block through a first HDMI-CEC port and in step  201 , acknowledging the CEC block. In step  202  modifying one or more bits in the received CEC block. And in step  203 , sending the modified CEC block through at least a second HDMI-CEC port. 
       FIG. 21  is a flow diagram illustrating one method comprising the following steps: In step  210 , receiving a CEC block comprising a destination logical address matching the initiator&#39;s HDMI-CEC network view. In step  211 , acknowledging the CEC block. In step  212 , modifying the destination logical address to match the follower&#39;s HDMI-CEC network view. And in optional step  213 , forwarding the modified block to the follower. 
     4) CEC Message Generation. 
     The CEC message generation function enables the manipulating switch to self generate one or more CEC blocks or one or more CEC messages, and supply the generated CEC message to a certain device(s). Optionally, the self generated CEC message is not initiated directly by a CEC message received by the manipulating switch. For example, the manipulating switch may generate a CEC message in order to perform one or more of the following: create an HDMI-CEC network view for a device, emulate a CEC message from a device, assign physical address to a CEC device, or spoof the HDMI-CEC cluster tree. By learning the HDMI network, the manipulating switch may create spoofed CEC transactions and/or spoof the address allocation process. 
     For example, referring again to  FIG. 6A  as an illustration of an HDMI-CEC network with two display devices  61  and  62 , display device  61  may be accessed by all source devices in the network and display device  62  may be accessed only by source devices  66  and  67 . While display device  61  retrieves its HDMI-CEC network view using the normal HDMI-CEC procedure, manipulating switch  64  prevents display device  62  from receiving the CEC transactions used for creating the HDMI-CEC network view exposed to display device  61 , optionally using the CEC propagation control function. During that process, manipulating switch  64  may learn the HDMI-CEC network topology and create spoofed CEC transactions used for creating the HDMI-CEC network view exposed to display device  62 , optionally using the CEC message generation function. 
     As another example, the manipulating switch may create an appropriate HDMI-CEC network view for each downstream and/or upstream path. In one embodiment, the manipulating switch creates the appropriate HDMI-CEC network view by spoofing CEC transactions using the CEC &lt;report physical address&gt; message that causes the addressed CEC device to report, to the other CEC devices in the HDMI-CEC cluster tree, the connection between its HDMI physical address and its CEC logical address. 
     In one example,  FIGS. 6A-C  illustrate manipulating switch  64  spoofing the CEC transactions for display device  62 , optionally using the CEC “report physical address” message. In this example, display device  61  receives an HDMI-CEC network view as if it were the only display device connected to the HDMI-CEC cluster tree, while display device  62  also receives an HDMI-CEC network view as if it were the only display device connected to the HDMI-CEC cluster tree. 
       FIG. 6B  illustrates the HDMI-CEC network view of display device  61 , where the physical addresses are denoted by a four digit number and the logical addresses are denoted inside brackets. The manipulating switch  64  makes sure that the various source devices receive the right physical addresses using the HDMI EDID distribution process with the EDID of display device  61 . After retrieving its physical address, each source device may assign itself a CEC logical address as known in the art. Then, each source device reports the connection between its logical and physical addresses using the &lt;report physical address&gt; CEC message. In the HDMI-CEC network view of display device  61  illustrated by  FIG. 6B , switch  63  receives the physical address 1.0.0.0, DVD  65  receives the physical address 1.1.0.0 and the logical address 4, switch  64  receives the physical address 1.2.0.0, STB  66  receives the physical address 1.2.1.0 and the logical address 3, and game console  67  receives the physical address 1.2.2.0 and the logical address 8. 
       FIG. 6C  illustrates the spoofed HDMI-CEC network view of display device  62 , where the physical addresses are denoted by a four digit number and the logical addresses are denoted inside brackets. HDMI-CEC does not support a multiple display architecture, therefore, the manipulating switch  64  spoofs the HDMI-CEC network view of display device  61  by self generating the appropriate CEC blocks that are supposed to be received and transmitted by source devices  66  and  67 . In the HDMI-CEC network view of display device  62  illustrated by  FIG. 6C , switch  64  receives the physical address 1.0.0.0, STB  66  receives the physical address 1.1.0.0 and the logical address 3, and game console  67  receives the physical address 1.2.0.0 and the logical address 8. 
     In one embodiment, the manipulating switch tries to maintain the same physical address and/or logical address assigned to each device in each of the HDMI-CEC network views. For example, source devices  66  and  67  in  FIGS. 6B and 6C  have the same logical addresses. 
     Examples of CEC Manipulation Operations 
     In some embodiments, one or more of the four basic CEC manipulation functions described above are used for the following CEC manipulation operations. 
     Manipulating the HDMI-CEC Network View. 
     In one embodiment, the manipulating switch manipulates the active sources existing in the HDMI-CEC network view of each display device.  FIG. 7  illustrates a case where display device  61  receives data from source device  73 . Because HDMI link  64   a  can carry only one stream, manipulating switch  64  has to disconnect the entire HDMI-CEC cluster tree connected by HDMI link  64   a  from the HDMI-CEC network view of display device  62 . In other words, the HDMI-CEC network view of display device  62  is manipulated according to the source-display stream activity and network topology. 
     In one embodiment, when a source device starts transmitting to a first display device, the manipulating switch may change the physical addresses of the rest of the network such that the rest of the network will be ready to transmit to the second display device. Alternatively, when a source device starts transmitting to a first display device, updating the physical addresses of the specific source device and its downstream devices is sufficient and there is no need to update the entire network regarding the change in the physical address of the active source device. 
       FIG. 22  is a flow diagram illustrating one method for discovering the CEC logical addresses of HDMI-CEC devices coupled to at least two HDMI-CEC ports of a manipulating switch, the method comprising performing the following steps for each HDMI-CEC port: In step  220 , generating CEC messages, wherein the generated CEC messages are optionally CEC polling messages. In step  221 , transmitting the generated CEC messages through the HDMI-CEC port. In step  222 , receiving replies to the transmitted CEC messages. In step  223 , not transmitting the received replies through the other HDMI-CEC ports. In step  224 , determining the CEC logical addresses of the HDMI-CEC devices coupled to the HDMI-CEC port from the received replies. And in optional step  225 , discovering the physical addresses of the HDMI-CEC devices coupled to the HDMI-CEC ports using CEC &lt;Give Physical Address&gt; messages. 
     In one embodiment, the following method steps are performed: Maintaining, by a manipulating switch, a first HDMI-CEC network view of a first HDMI-CEC display device and a second HDMI-CEC network view of a second HDMI-CEC display device, wherein the first and the second HDMI-CEC network views comprise a first HDMI-CEC source device that is common to both HDMI-CEC network views, whereby the common device defines the overlapping HDMI-CEC cluster tree. And approximately while there is TMDS communication between the first HDMI-CEC source device and the first HDMI-CEC display device, disconnecting the HDMI-CEC sub cluster tree associated with a first HDMI-CEC input port of the manipulating switch, which comprises the first HDMI-CEC source device, from the HDMI-CEC devices located in a second non-overlapping HDMI-CEC cluster tree. Optionally, the step of disconnecting the HDMI-CEC sub cluster tree may occur approximately when identifying one or more of the following CEC messages: &lt;set stream path&gt;, &lt;active source&gt;, &lt;image view on&gt;, or &lt;text view on&gt;. 
     Assigning the Same Physical Addresses to Different HDMI-CEC Cluster Trees. 
     In one embodiment, CEC propagation control is used with CEC broadcast messages, such as “report physical address”, and when at least two subsets of at least two overlapping or partially overlapping HDMI-CEC network views share the same physical and logical addresses or share the same logical addresses. Therefore, the manipulating switch tries to create a situation where the same device holds the same physical and logical addresses, or just the same logical address, in two or more HDMI-CEC network views. 
     Referring to  FIG. 7  as an example, the manipulating switch  64  may identify the more complicated physical address tree of the two HDMI-CEC cluster trees, optionally by comparing the physical address received in the HDMI output port connected to  63   b  with the physical address received in the HDMI output port connected to  62   a . Then the manipulating switch assigns its upstream devices physical addresses meeting the more complicated physical address tree. In the example of  FIG. 7  the more complicated physical address tree is the HDMI-CEC cluster tree of display device  61 . Then the manipulating switch generates spoofed report physical address CEC messages that are transferred to the less complicated physical address tree, which is the HDMI-CEC cluster tree of display device  62  in the example of  FIG. 7 . The manipulating switch  64  may create the HDMI-CEC network view of display device  62  by generating “report physical address” CEC messages that are transferred to the display device  62 . 
     In one embodiment, a method for assigning a required physical address to an HDMI-CEC device, comprising: determining by a manipulating switch the required HDMI physical address to be assigned to an upstream HDMI-CEC device, and providing the required HDMI physical address to the upstream HDMI-CEC device. Wherein the required HDMI physical address is different from the true HDMI physical address that should have been assigned according to the standard HDMI procedure for computing an HDMI physical address. 
     In one embodiment, a method operating a network comprising at least two HDMI-CEC display devices with their associated at least two HDMI-CEC cluster trees that at least partially overlap, comprising: identifying a set of HDMI physical addresses to be assigned to the HDMI-CEC devices in at least one upstream HDMI-CEC sub cluster tree of a manipulating switch, whereby these HDMI physical addresses will be consistent in the HDMI-CEC network views of the first and the second HDMI-CEC display devices. 
     Manipulating the Logical Address of a Device in the HDMI-CEC Cluster Tree. 
     The logical address of a device describes the device&#39;s functionality. The HDMI-CEC cluster tree is limited in the total number of devices it can contain (for example up to 10 devices) and in the number of devices of the same type it can contain (for example one audio system and four tuners). For example, section “CEC 10.2 Logical Addressing” in the HDMI specification version 1.3a describes the available logical addresses. 
     Referring again to  FIG. 7 , assuming source devices  65 ,  72 ,  73 , and  74  are playback devices, but the HDMI-CEC cluster tree supports only up to 3 playback devices. Therefore, display device  61  should see only three source devices, while display device  62 , which cannot receive streams from source device  65  (because HDMI link  63   b  is asymmetric), should see all the three source devices from which it can receive streams ( 72 ,  73 ,  74 ). Assuming source device  72  is disconnected from the HDMI-CEC cluster tree, source devices  65 ,  73  and  74  are visible to display device  61 , while only source devices  73  and  74  are visible to display device  62 . When source device  72  is connected to the HDMI-CEC cluster tree, manipulating switch  64  sees source devices  73 ,  74  and  72 , but the HDMI-CEC network view of display device  61  cannot include 4 playback devices in a standard HDMI-CEC cluster tree and this may be solved by one of the following two non-limiting examples. 
     A first example of assigning a valid logical address includes the following steps: 
     Playback device  72  wakes up and because HDMI-CEC cluster tree of display device  61  already contains three playback devices, playback device  72  cannot allocate a playback device CEC logical address. 
     While playback device  72  tries to receive its appropriate logical address, the other sources identify themselves, and as a result the manipulating switch  64  holds an updated network topology of the source devices having the same function. 
     Then manipulating switch  64  checks if it is possible to assign to playback device  72  a logical address in the HDMI-CEC cluster tree of display device  62 , so that the HDMI-CEC network view of display device  62  will include playback device  72  with its true logical address. This may be possible because source device  65  is under switch  63  and therefore is not accessible by display device  62 . 
     If it is possible, the manipulating switch  64  causes playback device  72  to reinitialize itself using the HPD signal, and then the manipulating switch  64  emulates the entire HDMI-CEC cluster tree of display device  62  in order for playback device  72  to receive the appropriate logical address. One example of an address allocation process includes the following steps: playback device  72  attempts to acquire a logical address by sending polling message to that address, and the manipulating switch  64  generates an answer for the logical addresses it does not want playback device  72  to acquire. 
     After source device  72  receives its appropriate logical address, the manipulating switch  64  may emulate source device  72  in order to notify display device  62  of the logical address of source device  72 . 
     A second example of assigning a valid logical address includes the following steps: 
     Still referring to  FIG. 7 , manipulating switch  64  creates for itself the downstream HDMI-CEC network view through his HDMI outputs, and calculates the logical addresses it should assign to the upstream devices ( 72 ,  73 , and  74 ). 
     Source device  72  wakes up as an HDMI-CEC device and the manipulating switch  64  assigns to source device  72  an address according to its preferences, by emulating the entire HDMI-CEC cluster tree. 
     Then the manipulating switch  64  checks whether a downstream device already owns the address assigned to source device  72 . If a downstream device already owns the address, manipulating switch  64  repeats the process so that source device  72  will receive a different address. 
       FIG. 8  illustrates a network example where a maximum number of 3 playback devices (having CEC logical addresses 8, 9, and 11) is allowed and already assigned to playback devices  81 ,  82 , and  83 . When playback device  84  connects to the network, the manipulating switch  64  has no available playback device logical address that is valid for both HDMI-CEC cluster trees. Therefore, the manipulating switch  64  assigns playback device  84  a logical address that meets one of the HDMI-CEC cluster trees and spoofs the other HDMI-CEC cluster tree. For example, manipulating switch  64  may actually assign the logical address 9 to playback device  84 , which is accepted by the HDMI-CEC network view of display device  61 , and spoof the HDMI-CEC network view of display device  62  to believe that playback device  84  holds the logical address 8. 
       FIG. 24  is a flow diagram illustrating one method for assigning a required CEC logical address to an HDMI-CEC source device, comprising the following steps: In step  240 , determining the required CEC logical address to be acquired by the HDMI-CEC source device. In step  241 , reinitializing the HDMI-CEC source device to acquire a CEC logical address utilizing polling messages. And in step  242 , spoofing the acknowledgements to polling messages containing CEC logical addresses other than the required CEC logical address. 
       FIG. 23  is a flow diagram illustrating one method comprising the following steps: In step  230 , dividing, by a manipulating switch, a plurality of HDMI-CEC devices into at least a first HDMI-CEC cluster tree coupled to a first HDMI-CEC display device, and a second HDMI-CEC cluster tree coupled to a second HDMI-CEC display device, wherein the HDMI-CEC cluster trees partially overlap. In step  231 , determining a first and a second HDMI-CEC network view for the first and the second HDMI-CEC display devices, whereby the two HDMI-CEC network views partially overlap. And in step  232 , enabling a second HDMI-CEC source device in the second HDMI-CEC cluster tree to acquire a required CEC logical address already in use by a first HDMI-CEC source device in the first HDMI-CEC cluster tree, wherein the first and the second HDMI-CEC source devices are located in the non-overlapping parts of the HDMI-CEC network views. 
     Assigning the Correct EDID To an Active Source. 
     In one embodiment, if a first display device sends a CEC &lt;set stream path&gt; message to a source device but the source device does not store the correct EDID of the first display device, the manipulating switch emulates the HDMI-CEC cluster tree in order to cause the active source device to have the correct EDID of the first display device. The manipulating switch is capable of knowing the correct EDID of the first display device using the  12   c  interface. Moreover, if the physical address assigned to the source device does not meet the HDMI-CEC network view of the first display device, the manipulating switch may also emulate the HDMI-CEC cluster tree in order to cause the active source device to have the required physical address. 
     Elimination of a Hierarchic Level in an HDMI-CEC network view. 
     HDMI limits the network view to include up to 4 hierarchic levels. In one embodiment, the manipulating switch eliminates one or more hierarchic levels from the HDMI-CEC network view of a display device.  FIG. 9  illustrates an example where the HDMI-CEC network views of both display devices  61  and  62  include 5 hierarchic levels. In order to be able to approach and control source device  94  using CEC, the manipulating switch  64  may eliminate, for example, the existence of switch  71  from the HDMI-CEC network views of display devices  61  and  62 .  FIG. 9  illustrates a case where the manipulating switch  64  spoofs the physical addresses of its upstream and downstream devices. As a result of implementing the physical address spoofing of eliminating the existence of switch  71 , the HDMI-CEC network views of both display devices  61  and  62  include no more than 4 hierarchic levels. As a result of implementing the physical address spoofing of eliminating the downstream devices of the manipulating switch  64 , it is possible to control devices  71 ,  72 ,  73 ,  74 , and  94  using CEC. It is to be understood that the described physical address spoofing method may be implemented on many more hierarchic levels, utilizing more manipulating switches. Moreover, the manipulating switch may always try to eliminate hierarchical levels in order to enable as many hierarchical levels as possible. 
     In one embodiment, the manipulating switch uses polling messages to verify, maintain and/or discover the CEC logical addresses of the network devices. The manipulating switch may check the logical address(es) from time to time in order to make sure that it stores an updated view of the network. 
     When the manipulating switch receives a polling message it knows whether it should answer with an ACK or not according to the stored HDMI-CEC network view(s). Referring again to  FIG. 8 , assume that the manipulating switch  64  receives a polling message from display device  62  containing the logical address of source device  73  in the HDMI-CEC network view of display device  62 . The manipulating switch replies with an ACK and does not forward the original message to source device  73  because it actually holds a different logical address in accordance with the HDMI-CEC network view of display device  61 . If needed, the manipulating switch may transmit to source device  73  a modified polling message containing its actual address. Similarly, the manipulating switch  64  may process polling messages from an upstream device to a downstream device. For example, a polling message from source device  73  containing the logical address of playback device  83  in the HDMI-CEC network view of display device  62  may be forwarded through HDMI link  62   a  if the message&#39;s address meets the actual address. Alternatively, the manipulating switch replies with an ACK and does not forward the original message to playback device  83 . If needed, the manipulating switch may transmit to playback device  83  a modified polling message containing its actual address. 
       FIG. 14  is a flow diagram illustrating one method for emulating an HDMI-CEC sub network, comprising the following steps: In step  140 , determining the properties of the HDMI-CEC sub network. In step  141 , generating CEC messages that emulate the CEC messages initiated by the HDMI-CEC sub network. And in step  142 , answering CEC messages addressed to the emulated HDMI-CEC sub network. 
       FIG. 25  is a flow diagram illustrating one method for manipulating HDMI-CEC messages transmitted over a network comprising at least a first and a second HDMI-CEC display device with their associated first and second HDMI-CEC cluster trees that at least partially overlap, the method comprising the following steps: In step  250 , monitoring the CEC &lt;Report Physical Address&gt; messages resulting from the physical address discovery process of the first and the second HDMI-CEC cluster trees. In step  251 , preventing the non-overlapping section of the second HDMI-CEC cluster tree from receiving the CEC messages initiated by the first HDMI-CEC cluster tree, and preventing the first HDMI-CEC cluster tree from receiving the CEC messages initiated by the non-overlapping section of the second HDMI-CEC cluster tree. In step  252 , preventing propagation of EDID associated with the non-overlapping section of the HDMI-CEC cluster tree to the first HDMI-CEC cluster tree. In step  253 , utilizing the CEC &lt;Report Physical Address&gt; messages resulting from the physical address discovery process of the first and the second HDMI-CEC cluster trees for learning the first and the second HDMI-CEC network views. In step  254 , spoofing CEC &lt;Report Physical Address&gt; messages from the overlapping section of the HDMI-CEC cluster tree towards the non-overlapping section of the second HDMI-CEC cluster tree. And in optional step  255 , determining the preferred physical and logical addresses to be acquired by the HDMI-CEC devices in the overlapping section of the HDMI-CEC cluster tree. 
     In one embodiment, when a message sender transmits a CEC message to a message recipient, the manipulating switch may intercept one or more of the CEC blocks, and answer with an ACK (the message may be directed downstream or upstream). Then the manipulating switch may transmit an appropriately modified or generated CEC blocks to the message recipient. If the message recipient does not accept the message or cannot perform the request, the manipulating switch may transmit a &lt;feature abort&gt; message to notify the message sender of the failure to execute the message. 
     Symmetric Channel 
       FIG. 11A  illustrates a symmetric communication channel  112  connecting between the manipulating switches  114  and  116 . If the symmetric communication channel  112  was a unidirectional communication channel and not a symmetric communication channel, display device  61  may have had access to source devices  65  and  66 , while display device  62  may have had access only to source device  66 . As a result of using the symmetric communication channel  112 , display device  62  may also access source device  65 . In the illustrated embodiment, the symmetric communication channel  112  does not influence the HDMI-CEC network view of display device  61 .  FIG. 11B  illustrates the physical addresses allocated to the HDMI-CEC network view of display device  61 . As illustrated, manipulating switch  114  may have manipulating switch  116  and source device  65  as its upstream devices. Therefore, manipulating switch  114  receives the physical address of (1.0.0.0), manipulating switch  116  receives the physical address of (1.1.0.0), source device  65  receives the physical address of (1.1.1.0), and source device  66  receives the physical address of (1.2.0.0). 
     It is to be understood that the symmetric channel may also be a multi-stream symmetric channel. A multi-stream symmetric channel may utilize the above described methods and devices for utilizing a multi-stream channel within an HDMI-CEC cluster trees, operating a multi-stream manipulating switch, calculating the residue bandwidth, ensuring enough bandwidth in advance, and/or operating a multi-stream daisy chain supporting HDMI-CEC. 
     NON-HDMI Cables 
     There are solutions for transmitting HDMI-CEC over non-standard HDMI cables, such as CAT5x, CAT6, coax, or fiber, wirelessly, or using any other solution that may be available today as well as in the future. The embodiments of the manipulating switch cover all of these alternative solutions and all of the alternative multimedia interfaces. For example, in  FIG. 2 , connection  12   a  may be an HDMI cable while connection  12   b  may be an optical fiber,  12   c  may be a CAT6 cable,  15   a  may be a coax cable, and  15   b  may be a wireless link. In other words, the various disclosed embodiments are not limited to some specific HDMI cable but may be implemented using any appropriate communication medium. 
       FIG. 10  illustrates a manipulating switch  180  having an HDMI cable input  183  that may be connected to an HDMI source device, a CAT5e input  184  that may be connected to an HDMI source device over a twisted pair system, wireless output  181  that may communicate with an HDMI display device over a wireless system and coax output  182  that may be connected to an HDMI display device over coax cable system. 
     Although the embodiments have been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. 
     Certain features of the embodiments, which may, for clarity, be described in the context of separate embodiments, may also be provided in various combinations in a single embodiment. Conversely, various features of the embodiments, which may, for brevity, be described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
     The embodiments are not limited in their applications to the details of the order or sequence of steps of operation of methods, or to details of implementation of devices, set in the description, drawings, or examples. 
     While the methods disclosed herein have been described and shown with reference to particular steps performed in a particular order, it will be understood that these steps may be combined, sub-divided, or reordered to form an equivalent method without departing from the teachings of the embodiments. Accordingly, unless specifically indicated herein, the order and grouping of the steps is not a limitation of the embodiments. 
     Any citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the embodiments of the present invention. 
     While the embodiments have been described in conjunction with specific examples thereof, it is to be understood that they have been presented by way of example, and not limitation. Moreover, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and scope of the appended claims and their equivalents. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures.