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.
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.
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.
As shown in
In an embodiment, HDMI transmitter 202 receives video, audio (in the form of an Audio In signal) and control signals 212, as illustrated in
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.
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.
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.
For these reasons, fiber optic cables are typically preferred over copper cables for long length DVI and HDMI signal extensions.
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.
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
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.
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.
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.
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.
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.
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.
Enhanced fiber HD content delivery systems are therefore desired.
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.
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.
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.
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.
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.
DVI system 700 uses no error concealment. However, as will be illustrated in the variant system of
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.
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.
In system 800 of
It is noted that the above described DVI systems of
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.
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
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.
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.
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
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.
HDMI system 900 of
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.
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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 60814879 | Jun 2006 | US |