Abstract:
A system, method, and apparatus that improves the efficiency of HD content delivery systems. An embodiment of the invention eliminates unnecessary encoding overhead due to TMDS encoding in HD content delivery systems. An embodiment of the invention further allows for increased error protection at lower overhead in HD content delivery systems. Furthermore, embodiments of the present invention provide less expensive and more efficient techniques for transmitting content protection information in HD content delivery systems. The invention is applicable to HD content delivery systems such as DVI and HDMI systems, including systems that employ novel data transmission techniques of the present invention as well as conventional content delivery systems. The invention is applicable to copper and fiber HD content delivery systems.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of U.S. Provisional Patent Application No. 60/814,879, entitled “System, Method and Apparatus for Transmitting High Definition Signals Over a Combiner Fiber and Wireless System” and filed on Jun. 20, 2006, the entirety of which is incorporated herein by reference. 
     
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention is generally related to generalized content distribution systems. More particularly, the present invention is directed to a system, method and apparatus for transmitting high definition (HD) signals over a combined fiber and wireless system. 
         [0004]    2. Background 
         [0005]    High Definition (HD) signals are typically transmitted from one system to another using cables carrying DVI (Digital Video Interface) or HDMI (High Definition Multimedia Interface) signals. 
         [0006]    Conventionally, DVI/HDMI signals are conveyed using a signaling scheme known as Transition Minimized Differential Signaling (TMDS). In TMDS, video, audio, and control data are carried as a series of 24-bit words on three TMDS data channels with a separate TMDS channel for carrying clock information. Additionally, DVI/HDMI systems may include a separate bi-directional channel known as the Display Data Channel (DDC) for exchanging configuration and status information between a source and a sink, including information needed in support of High-Bandwidth Digital Content Protection (HDCP) encryption and decryption. In HDMI, an optional Consumer Electronic Control (CEC) protocol provides high-level control functions between audiovisual products. 
         [0007]    TMDS was initially designed for DVI/HDMI transmission over copper cables. However, the trend in DVI/HDMI systems is for using fiber optic cables instead of copper cables for distances spanning more than 5 meters. 
         [0008]    In several respects, TMDS signaling is less than optimal for DVI/HDMI transmission over fiber. For example, DC-balancing and transition minimization characteristics of TMDS increase signaling overhead but provide little gain over fiber. Further, the BCH (Bose, Ray-Chaudhuri, Hocquenghem) code used in TMDS signaling is significantly inferior to other codes that provide greater error protection at lower overhead. 
         [0009]    In another aspect, conventional DVI/HDMI systems continue to use bulky and expensive copper cables for conveying DDC information in the case of conventional DVI systems and DDC/CEC information in the case of conventional HDMI systems. 
         [0010]    What is needed therefore is a system, method, and apparatus that reduces TMDS signaling overhead in DVI/HDMI transmission over fiber while providing greater error protection. What is further needed is to eliminate the bulky and expensive copper cables used for conveying DDC information in conventional DVI systems and for conveying DDC/CEC information in conventional HDMI systems. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    The present invention is directed to a system, method, and apparatus for improving the efficiency of HD content delivery systems. An embodiment of the present invention eliminates unnecessary encoding overhead due to TMDS encoding in HD content delivery systems. Additionally, an embodiment of the present invention provides increased error protection at lower overhead in HD content delivery systems. Furthermore, embodiments of the present invention provide less expensive and more efficient techniques for transmitting content protection information in HD content delivery systems. 
         [0012]    The present invention is applicable to HD content delivery systems such as DVI and HDMI systems, including systems that employ novel data transmission techniques as will be described herein as well as conventional content delivery systems. The present invention is also applicable to copper and fiber HD content delivery systems. 
         [0013]    Further features and advantages of the invention, as well as the structure and operation of various embodiments of the invention, are described in detail below with reference to the accompanying drawings. It is noted that the invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Additional embodiments will be apparent to persons skilled in the relevant art(s) based on the teachings contained herein. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0014]    The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention. 
           [0015]      FIG. 1  illustrates a conventional DVI content delivery system. 
           [0016]      FIG. 2  illustrates a conventional HDMI content delivery system. 
           [0017]      FIG. 3  illustrates a conventional DVI fiber content delivery system. 
           [0018]      FIG. 4  illustrates a conventional HDMI fiber content delivery system. 
           [0019]      FIG. 5  illustrates a single fiber DVI content delivery system. 
           [0020]      FIG. 6  illustrates a single fiber HDMI content delivery system. 
           [0021]      FIG. 7  illustrates a single fiber DVI content delivery system with wireless Display Data Channel (DDC) and end-to-end High Definition Digital Content Protection (HDCP) without error concealment. 
           [0022]      FIG. 8  illustrates a single fiber DVI content delivery system with wireless DDC and three HDCP sessions with error concealment. 
           [0023]      FIG. 9  illustrates a single fiber HDMI content delivery system with wireless DDC/CEC and end-to-end HDCP without error concealment. 
           [0024]      FIG. 10  illustrates one implementation according to the present invention for wirelessly implementing the DDC channel in a DVI/HDMI content delivery system. 
       
    
    
       [0025]    The features and advantages of the present invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number. 
       DETAILED DESCRIPTION OF THE INVENTION 
     A. Overview 
       [0026]      FIG. 1  illustrates a conventional DVI (Digital Video Interface) content delivery system  100 . DVI system  100  includes a DVI transmitter  102  and a DVI receiver  104  connected by a DVI link  106 . DVI link  106  is used to convey video information from DVI transmitter  102  to DVI receiver  104 . Typically, DVI link  106  is a copper cable with DVI signals transmitted over the link using the Transition Minimized Differential Signaling (TMDS) scheme. In accordance with TMDS, video and control data are carried as a series of 24-bit words on three TMDS data channels with a separate TMDS channel used for carrying clock information. This is illustrated in  FIG. 1  using channels TMDS 0 , TMDS 1 , TMDS 2 , and CLK. In an embodiment, the 24-bit words are protected using High-Bandwidth Digital Content Protection (HDCP), enabled by a HDCP Encryption module  108  at DVI transmitter  102  and a HDCP decryption module  110  at DVI receiver  104 . HDCP provides protection against unauthorized reproduction of copyrighted content. TMDS encoding converts the HDCP-encrypted 8 bits per channel into 10 bits providing DC-balancing, transition minimization, and error protection via a BCH code. 
         [0027]    Additionally, DVI system  100  includes a separate bi-directional channel  120  known as the Display Data Channel (DDC), which is used for configuration and status exchange between DVI transmitter  102  and DVI receiver  104 . This configuration exchange may include information needed in support of HDCP. 
         [0028]    As shown in  FIG. 1 , DVI transmitter  102  receives video and control signals  112  in the form of an Active Video Period Indicator signal, a Video In signal, HSYNC and VSYNC signals, and control signals CTL 0 - 3 . DVI transmitter  102  applies HDCP encryption to the received video and control signals  112 , encodes the encrypted signals using TMDS, and transmits the encoded signals over the copper DVI link  106 . DVI receiver  104  receives the transmitted DVI signals, removes the TMDS encoding, and performs HDCP decryption to generate the video and control signals  114 . In the absence of transmission errors, video and control signals  114  are identical to video and control signals  112  (except that signals  114  contain no Active Video Period Indicator signal). Concurrently, configuration and status signals  116  and  118  are exchanged between DVI transmitter  102  and DVI receiver  104  over DDC channel  120  of DVI link  106 . Note that the exchange on DDC channel  120  may occur from DVI transmitter  102  to DVI receiver  102 , and vice versa. 
         [0029]      FIG. 2  illustrates a conventional HDMI content delivery system  200 . HDMI system  200  is similar in several respects to DVI system  100  of  FIG. 1 , as will be appreciated by persons skilled in the art. HDMI system  200  includes an HDMI transmitter  202  and an HDMI receiver  204  connected by an HDMI link  206 . HDMI link  206  is a copper cable, with HDMI signals transmitted over HDMI link  206  using TMDS, in a similar manner to that described above with respect to  FIG. 1 . Further, HDMI link  206  is HDCP protected by virtue of the operation of a HDCP Encryption module  208  at DVI transmitter  202  and a HDCP Decryption module  210  at DVI receiver  204 . 
         [0030]    In an embodiment, HDMI transmitter  202  receives video, audio (in the form of an Audio In signal) and control signals  212 , as illustrated in  FIG. 2 . HDMI transmitter  202  applies HDCP encryption using HDCP encryption module  208  to the received signals  212 , encodes the encrypted signals using TMDS, and then transmits the encoded signals over copper HDMI link  206 . At the receiver end, HDMI receiver  204  receives the transmitted HDMI signals, removes the TMDS encoding, and performs HDCP decryption using HDCP Decryption module  210  to generate the video, audio and control signals  214 . In the absence of transmission errors, video, audio, and control signals  214  are identical to video, audio, and control signals  212  (except that signals  214  contain no Active Video Period Indicator signal). 
         [0031]    Similar to DVI system  100 , configuration and status signals  216  and  218  are exchanged between HDMI transmitter  202  and HDMI receiver  204  over DDC channel  224  of HDMI link  206 . Optionally, HDMI transmitter  202  and HDMI receiver  204  also exchange CEC information signals  220  and  222  over DDC channel  224 , which is used to convey high-level control functions between audiovisual products. In an embodiment, the CEC information may be embedded together with the DDC information and transmitted over the same DDC/CEC channel of HDMI link  206 . 
       B. Conventional Fiber HD Content Delivery Systems 
       [0032]    As described above with respect to systems  100  and  200 , conventional DVI/HDMI systems employ copper cables for conveying information from one system to another. Using TMDS, DC-balancing and transition minimization can be achieved making copper cables efficient for DVI/HDMI systems spanning distances that are less than approximately 5 meters. 
         [0033]    However, for longer distances, the impedance of copper cables causes large signal loss resulting in DVI and HDMI artifacts such as sparkles, pixilation, and loss of picture. While signal boosters and other approaches may be used over copper cables to reduce signal loss, these techniques are costly and not always effective. In contrast, relatively low cost fiber optic cables provide high quality transmissions at great distances due to the signal fidelity and noise immunity achievable over fiber. Further, fiber cables provide additional benefits compared to copper cables including longer lifetime and small cable size. 
         [0034]    For these reasons, fiber optic cables are typically preferred over copper cables for long length DVI and HDMI signal extensions. 
         [0035]      FIG. 3  illustrates a conventional DVI fiber content delivery system  300 . Starting with TMDS encoded DVI signals  302 , an optical transmitter  304  such as a 4-channel Vertical Cavity Surface Emitting Laser (VCSEL) is used to directly convert the TMDS encoded DVI signals  302  into 4 optical signals  310 -{ 1 , . . . , 4 }. Optical signals  310 -{ 1 , . . . , 4 } are transmitted as light pulses over 4 separate unidirectional fiber channels contained in fiber link  306 . At the receiver side, an optical detector  308  such as a PIN or avalanche photodiode is used to convert each of fiber channels  310 -{ 1 , . . . , 4 } back into a TMDS channel, thereby recovering the original TMDS encoded DVI signals  302 . 
         [0036]    Note that DDC channel  120  continues to be carried over a twisted pair of copper wires in DVI fiber system  300 . This is generally acceptable, even for longer distances, given the low rate nature of DDC transmissions. 
         [0037]      FIG. 4  illustrates a conventional HDMI fiber content delivery system  400 . HDMI system  400  is substantially similar to DVI system  300  of  FIG. 3 , as will be understood by persons skilled in the art. Similar to DVI system  300 , an optical transmitter  404  is used to convert TMDS encoded HDMI signals  402  into optical signals  410 -{ 1 , . . . , 4 } and to transmit optical signals  410 -{ 1 , . . . , 4 } over 4 separate unidirectional fiber channels. The 4 unidirectional fiber channels are contained in a fiber link  406 . At the receiver side, an optical receiver  408  is used to recover optical signals  410 -{ 1 , . . .  4 } and reconvert them into TMDS encoded signals  402 , which are fed to HDMI receiver  204 . The DDC/CEC channel  224  continues to be carried by copper cables in HDMI fiber system  400 . 
       C. Single Fiber HD Content Delivery Systems 
       [0038]    Conventional fiber DVI/HDMI systems may be further improved by aggregating the 4 TMDS encoded fiber channels into a single fiber link. This is illustrated in  FIGS. 5 and 6 , which respectively illustrate single fiber DVI and single fiber HDMI content delivery systems  500  and  600 . In an embodiment, a 4:1 digital interface  502  ( 602 ) is used between DVI transmitter  102  (HDMI transmitter  202 ) and optical transmitter  304  ( 404 ) to multiplex the 4 TMDS encoded signals  302  ( 402 ) onto a single aggregate digital signal  506  ( 606 ). Aggregate digital signal  506  ( 606 ) is then optically converted by optical transmitter  304  ( 404 ) and transmitted over an aggregate fiber channel  508  ( 608 ). At the receiver side, an optical receiver  308  ( 408 ) re-generates aggregate digital signal  506  ( 606 ), before providing it to a 1:4 digital interface  504  ( 604 ) which re-generates the 4 multiplexed TMDS encoded signals  302  ( 402 ). 
         [0039]    Note that using an aggregate fiber channel  508  ( 608 ) simplifies the DVI/HDMI content delivery system by allowing for the use of a one-channel laser and photodiode. On the other hand, aggregate fiber channel  508  ( 608 ) typically has a higher data rate, often necessitating more expensive fiber, laser, and photodiode. 
         [0040]    It is noted that DDC channel  120  of system  500  and DDC/CEC channel  224  of system  600  still require a separate transmission medium, which typically includes a twisted pair of copper wires. 
       D. Improved Single Fiber HD Content Delivery System 
       [0041]    As described above, conventional DVI/HDMI fiber content delivery systems continue to employ TMDS encoding for conveying information. TMDS, however, initially designed for copper cables, provides little gain in fiber systems but results in added encoding overhead. 
         [0042]    It is desirable to reduce the amount of overhead due to TMDS encoding in fiber systems, especially in single fiber HD systems which use a high data rate aggregate fiber channel. This is the case because reducing the amount of overhead allows for a reduction in the required data rate of the aggregate channel, thereby allowing for system operation using less-expensive and less-bulky components such as lasers, fibers, and photodiodes. 
         [0043]    Additionally, error protection as provided by TMDS using a BCH code is considerably inferior compared to error protection using other types of codes with lower overhead such as low density parity check (LDPC) codes, for example. It is therefore desirable to provide greater error protection for data transmissions while reducing the overhead due to the error protection code. 
         [0044]    Further, conventional DVI/HDMI systems continue to use bulky and expensive copper cables for conveying DDC information in the case of DVI and DDC/CEC information in the case of HDMI. 
         [0045]    Enhanced fiber HD content delivery systems are therefore desired. 
         [0046]      FIG. 7  illustrates a single fiber DVI content delivery system  700  with wireless Display Data Channel (DDC) and end-to-end High Definition Digital Content Protection (HDCP) without error concealment, in accordance with an embodiment of the present invention. DVI system  700  uses a TMDS decoder  702  at the transmitter side, which removes the TMDS encoding and re-generates the underlying HDCP-encrypted video and control information  704 . Subsequently, Forward Error Correction (FEC) and/or Fiber Frame Formatting, customized for optical transmissions, is applied to video and control information  704  using FEC Encoding/Fiber Frame Formatting module  706 . In an embodiment, a rate ⅞, length 8192 low density parity check (LDPC) code is applied for video data and a variable length and rate Reed-Solomon (RS) code is applied for control information to provide error protection. Typically, the length of the RS code depends on the amount of control information to be transmitted in a particular vertical blanking interval (VBI). As such, no additional overhead is added for DC-balancing or transition minimization, resulting in an aggregate data rate of aggregate digital signal  708  substantially lower than required to convey TMDS encoded signals. This allows for cost reduction in terms of the optical components (lasers, fibers, and photodiodes) of the system. 
         [0047]    At the receiver side of system  700 , once aggregate digital signal  708  is recovered by optical receiver  308 , LDPC and RS decoders are applied to recover the video and control information  712  respectively. These operations are performed by FEC Decoding/Fiber Frame De-Formatting module  710 . Subsequently, the FEC decoded video and control information  712  is fed to a TMDS encoder  714 , which regenerates TMDS signals  302  and passes these TMDS signals to DVI receiver  104 . 
         [0048]    Note that in system  700 , a single fiber  508  is used to convey the FEC encoded information from DVI transmitter  102  to DVI receiver  104 . Accordingly, FEC encoding is applied to an aggregate signal onto which are multiplexed alternating samples from each of the 4 TMDS decoded outputs  704 , to generate aggregate digital signal  708 . Alternatively, in a system using separate fiber channels for each of TMDS decoded outputs  704 , separate FEC encoders and decoders can be used for each channel. 
         [0049]    In addition to reducing overhead due to TMDS encoding and error protection, DVI system  700  uses a wireless channel  720  to convey DDC information. This eliminates the expensive and bulky copper cables used in conventional systems. In an embodiment, a wireless channel in the 902-928 MHz frequency band is used to communicate DDC information between DVI transmitter  102  and DVI receiver  104 . Note that the 902-928 MHz band is an FCC regulated ISM frequency band that supports reliable transmissions over long distances in the United States. Alternatively, other frequency allocations may be used according to local regulatory conditions. For example, the 868 MHz ISM band can be used in Europe. 
         [0050]    In an embodiment, DDC information is sent from DVI transmitter  102  to a wireless transceiver  716  at the transmitter side, which encodes the information for wireless transmission and transmits the information over wireless channel  720 . A wireless transceiver  718  at the receiver side receives the wireless information and re-generates the DDC information, before sending it to DVI receiver  104 . It is noted that DDC channel  720  is bidirectional, and therefore DDC information may also be transmitted in the receiver-to-transmitter direction. 
         [0051]    In other embodiments, the DDC information is multiplexed together with video and control information on aggregate fiber channel  508  in the transmitter-to-receiver direction, and carried wirelessly in the receiver-to-transmitter direction, or vice versa. 
         [0052]    DVI system  700  uses no error concealment. However, as will be illustrated in the variant system of  FIG. 8 , error concealment can be implemented, for example, in the TMDS encoder at the receiver side. In such an embodiment, data from the LDPC and RS decoders (FEC Decoding module  710 ) indicating the reliability of the decoded video can be used for video error concealment. For example, if the LDPC decoder marks a video pixel as being in error, that pixel can be estimated from surrounding pixels that are known to be reliable. 
         [0053]    The ability to perform error concealment is determined by the particular HDCP configuration. This is because the HDCP configuration determines whether or not raw (i.e., unencrypted) video samples are available for error concealment. Typically, HDCP encryption performs an XOR operation on the data, making error concealment impossible prior to HDCP decryption. The present invention can be used with many HDCP variants. 
         [0054]    In DVI system  700 , HDCP encryption is applied end-to-end from DVI transmitter  102  to DVI receiver  104 . Therefore, there can be no error concealment at TMDS encoder  714  because FEC decoded video and control signals  712  remain HDCP-encrypted at TMDS encoder  714 . 
         [0055]    In system  800  of  FIG. 8 , a first HDCP session is initiated using HDCP Encryption module  108  at DVI transmitter  102  and terminated at TMDS decoder  802  using HDCP Decryption module  804 , a second HDCP session is initiated using HDCP Encryption module  806  at TMDS decoder  802  and terminated at TMDS Encoder  808  using HDCP Decryption module  810 , before a third HDCP session is initiated using HDCP Encryption module  814  at TMDS encoder  808  and terminated at DVI receiver  104  using HDCP Decryption module  110 . As such, raw (i.e., unencrypted) data is available at TMDS encoder  808  at the termination of the second HDCP session, allowing for error concealment to be performed before TMDS encoder  808  initiates the third HDCP session. 
         [0056]    It is noted that the above described DVI systems of  FIGS. 7 and 8  may be equivalently implemented as HDMI systems, including all of the above described embodiments thereof.  FIG. 9  illustrates, for example, a single fiber HDMI content delivery system  900  with wireless DDC/CEC and end-to-end HDCP without error concealment, similar to DVI system  700  of  FIG. 7 . 
         [0057]    HDMI system  900  uses a TMDS decoder  902  at the transmitter side, which removes the TMDS encoding and re-generates HDCP-encrypted audio, video and control signals  904 . Subsequently, Forward Error Correction (FEC) and/or Fiber Frame Formatting, customized for optical transmissions, are applied to audio, video and control signals  904 . In an embodiment, a rate ⅞, length 8192 low density parity check (LDPC) code is applied for video data and a variable length and rate Reed-Solomon (RS) code is applied for audio and control information to provide error protection. Typically, the length of the RS code depends on the amount of control information to be transmitted in a particular audio/video (AV) line. As such, no additional overhead is added for DC-balancing or transition minimization, resulting in an aggregate data rate of aggregate digital signal  908  substantially lower than required to convey TMDS encoded signals. This allows for cost reduction in terms of the optical components (lasers, fibers, and photodiodes) of the system. 
         [0058]    At the receiver side of system  900 , LDPC and RS decoders are applied to recover video, audio, and control signals  912 . This is illustrated using the FEC Decoding/Fiber Frame De-Formatting module  910  in  FIG. 9 . Note that signals  912  should be identical to respective signals  904  (except that signals  912  contain no Active Video Period Indicator signal), unless uncorrectable errors occur in transmission. Subsequently, FEC decoded video, audio and control signals  912  are fed to a TMDS encoder  914 , which regenerates TMDS signals  402  and passes these TMDS signals to HDMI receiver  204 . 
         [0059]    Note that in system  900 , a single fiber is used to convey the FEC encoded information from HDMI transmitter  202  to HDMI receiver  204 . Accordingly, FEC encoding is applied to an aggregate signal onto which are multiplexed alternating samples from each of the 5 TMDS decoded outputs  904 , to generate aggregate signal  908 . Alternatively, in a system using separate fiber channels for each of TMDS decoded outputs  904 , separate FEC encoders and decoders can be used for each channel. Alternatively, the TMDS outputs  904  can be grouped into one or more outputs per group and separate FEC encoders and decoders used on each grouped signal. 
         [0060]    In addition to reducing overhead due to TMDS encoding and error protection, HDMI system  900  uses a wireless channel  920  to convey the DDC/CEC information. This eliminates the expensive and bulky copper cables used in conventional systems. In an embodiment, a wireless channel in the 902-928 MHz frequency band is used to communicate DDC/CEC information between the HDMI transmitter and the HDMI receiver. Note that the 902-928 MHz band is an FCC regulated ISM frequency band that supports reliable transmissions over long distances in the United States. Alternatively, other frequency allocations may be used according to local regulatory conditions. For example, the 868 MHz ISM band can be used in Europe. 
         [0061]    In an embodiment, DDC/CEC information is sent from HDMI transmitter  202  to a wireless transceiver  916  at the transmitter side, which encodes the information for wireless transmission and transmits the information over wireless channel  920 . At the receiver side, a wireless transceiver  918  receives the wireless information and re-generates the DDC/CEC information, before sending it to HDMI receiver  204 . It is noted that DDC channel  920  is bidirectional, and therefore DDC information may also be transmitted in the receiver-to-transmitter direction 
         [0062]    In other embodiments, the DDC/CEC information is multiplexed together with video, audio, and control information on aggregate fiber channel  608  in the transmitter-to-receiver direction and carried wirelessly in the receiver-to-transmitter direction, or vice versa. 
         [0063]    HDMI system  900  of  FIG. 9  uses no error concealment. However, error concealment could be implemented if a different HDCP configuration were used that made raw (i.e., unencrypted) audio and video samples available at TMDS encoder  914 . Such an HDCP configuration is illustrated in DVI system  800  of  FIG. 8 , and can be readily extended to an HDMI system. In such an embodiment, data from the LDPC and RS decoders (FEC Decoding module  910 ) indicating the reliability of the decoded video and audio could be used for video and audio error concealment. For example, if the LDPC decoder marked a video pixel as being in error, that pixel could be estimated from surrounding pixels that are known to be reliable. 
       E. Combined Fiber and Wireless Content Delivery Systems 
       [0064]    As described above with respect to various embodiments according to the present invention, the DDC/CEC channel can be implemented wirelessly either uni-directionally or bi-directionally, eliminating the need for expensive and bulky copper cables. This advantage according to the present invention is not limited to systems employing embodiments of the present invention for transmitting audio, video, and control information, but can be extended to conventional fiber and copper content delivery systems.  FIG. 10 , for example, illustrates a fiber DVI system  1000  that wirelessly implements the DDC channel  720 . This can be similarly extended to conventional copper DVI systems or to conventional HDMI fiber/copper systems. 
       D. Conclusion 
       [0065]    While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be understood by those skilled in the relevant art(s) that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. Accordingly, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.