Method and Apparatus for Improving Transmission of Transport Video Signal

Abstract

A method and an apparatus for improving digital video signal transmission over a long transmission line are disclosed. A simple equalization reference signal is generated and then combined with a digital video signal in the digital domain such that the transmission of the reference signal takes place at a predefined time period during the vertical blanking interval of the video signal. The combined signal is then converted into an analog video transport signal, which analog signal is then transmitted over the long transmission line to a downstream video receiver. The equalization reference signal is extracted and used at the video receiver to restore the analog video signal which in turn is converted back to digital video signal.

Claims

1. A method for improving digital video signal transmission over a transmission line, the method comprising: generating an equalization reference signal; combining, in the digital domain, the generated equalization reference signal with a digital video signal such that the transmission of the reference signal takes place at a predefined time period during the vertical blanking interval of the video signal; converting the combined digital signal into an analog video transport signal; and transmitting the analog video transport signal over the transmission line to a downstream video receiver wherein the equalization reference signal is extracted and used to restore the digital video signal.

2. The method of claim 1, wherein the equalization reference signal is generated for each vertical blanking interval of the display of the video signal.

3. The method of claim 1, wherein the combining consists of multiplexing the equalization reference signal at a predefined time that corresponds to a predefined subsection of each vertical blanking interval of the display of the video signal.

4. The method of claim 1, wherein the equalization reference signal is a single impulse signal of a predefined frequency.

5. The method of claim 3, wherein the predefined section of each vertical blanking interval is one or more horizontal lines that are not used for vertical synchronization.

6. The method of claim 1, further comprising generating a control sequence to be transmitted during the vertical blanking interval of the display of the video signal and the combining consists of combining both the control sequence and the equalization reference signal.

7. The method of claim 6, wherein the composition of the control data information of the control sequence is programmable.

8. The method of claim 6, wherein the control sequence is transmitted at a time period during the vertical blanking interval but different from that of the equalization reference signal.

9. The method of claim 7, wherein the control sequence consists of a start sequence of a predefined number of bits immediately followed by control data.

10. The method of claim 8, wherein the control sequence is transmitted consecutively and immediately after a control sequence start bit.

11. The method of claim 2, wherein the equalization reference signal is a single tone signal of a predefined frequency.

12. A method for improving video signal transmission over a transmission line, the method comprising: generating a control data sequence with a predefined length; combining, in the digital domain, the generated control data sequence with a digital video signal such that the time for the transmission of the reference signal takes place at a predefined time period during the vertical blanking interval of the video signal; converting the combined digital signal into an analog video transport signal; and transmitting the analog video transport signal over the transmission line to a downstream video receiver wherein the control data sequence is extracted and used to restore the digital video signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] These and other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures, wherein:

[0010] FIG. 1 illustrates an encoder system on the camera side where an embodiment of the present invention is applicable.

[0011] FIG. 2 illustrates the allocation of an equalization reference signal and control data during a vertical blanking interval of a typical 1280×720P video signal according to one embodiment of the invention.

[0012] FIG. 3 illustrates a timing diagram of a single-tone equalization reference signal transmitted during a horizontal line of a VBI according to one embodiment of the invention.

[0013] FIG. 4 illustrates the transmission of control data during a horizontal line of a VBI of a video signal according to a prior art.

[0014] FIG. 5 illustrates the transmission of control data during a horizontal line of a VBI of a video signal according to one embodiment of the invention.

[0015] FIG. 6 illustrates a flow chart of a method for sending an equalization reference signal and optionally a control sequence during the VBI according to one embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will now be described in detail with reference to the drawings, which are provided as illustrative examples of the invention so as to enable those skilled in the art to practice the invention. Notably, the figures and examples below are not meant to limit the scope of the present invention to a single embodiment, but other embodiments are possible by way of interchange of some or all of the described or illustrated elements.

[0017] Moreover, where certain elements of the present invention can be partially or fully implemented using known components, only those portions of such known components that are necessary for an understanding of the present invention will be described, and detailed descriptions of other portions of such known components will be omitted so as not to obscure the invention.

[0018] Embodiments described as being implemented in software should not be limited thereto, but can include embodiments implemented in hardware, or combinations of software and hardware, and vice-versa, as will be apparent to those skilled in the art, unless otherwise specified herein. In the present specification, an embodiment showing a singular component should not be considered limiting; rather, the invention is intended to encompass other embodiments including a plurality of the same component, and vice-versa, unless explicitly stated otherwise herein. Moreover, applicants do not intend for any term in the specification or claims to be ascribed an uncommon or special meaning unless explicitly set forth as such. Further, the present invention encompasses present and future known equivalents to the known components referred to herein by way of illustration.

[0019] FIG. 1 illustrates an encoder system on the camera side where an embodiment of the present invention is applicable.

[0020] The major functional blocks of a camera side encoder (100) include the data/sync processor (102), the digital VBI signal generator (104), the summer (or, combiner)(106) and the D/A converter (108) and the downstream receiver (112) at the other end of the transmission line (110).

[0021] In some embodiments, an integrated data/sync processor 102 implements both data processing and synchronization signal generation. In some other embodiments, the data/sync processor 102 as drawn in FIG. 1 may actually consist of two separate processors: a data processor and a sync processor.

[0022] In some embodiments, the function of a sync processor includes extracting the sync information (EAV/SAV) in the input data stream (luminance data YD and Chrominance data CD) and generating both horizontal and vertical syncs through a timing generator (not shown). In some embodiments, the sync processor can generate horizontal and vertical syncs from signals separate from the input data stream.

[0023] The function of a data processor includes preparing the data for encoding by scaling, shifting, limiting, filtering and modulation. The processed luminance data (Y) and Chrominance data (U/V) are sent to Summer 106.

[0024] The VBI signal generator 104 generates the equalization reference signal and/or control data in response to the host command. The summer 106 combines all the digital input from both Sync/Data Processor 102 and VBI Data Generator 104 based on the timing signals from the timing generator. The digital output of Summer 106 is then converted to analog signal through D/A converter 108. The converted signal is sent through a cable or transmission media 110. At the receiver 112, the process is reversed to recover the original digital data, the embedded sync information as well as the control data.

[0025] FIG. 2 illustrates the timing allocation of an equalization reference signal and a control sequence during a vertical blanking interval of a 1280×720P video signal according to one aspect of the invention. As a non-limiting example, in SMPTE 296M standard, a 1280×720P video has 750 horizontal lines, of which 30 lines are vertical blanking interval. According to the numbering scheme of SMPTE 296M, horizontal lines 1-25 and 746-750 are designated for VBI and horizontal lines 26-745 are active video frame data. SMPTE 296M only defines and uses a subset of the VBI lines (e.g., 1-6 horizontal lines) for transmission of specific data, such as a vertical synchronization pulse. This leaves the rest of the VBI lines open for various other applications.

[0026] According to some embodiments of this invention, the equalization reference signal (202) is a single burst of sine wave that is transmitted during VBI line 749 as depicted in FIG. 2, and various proprietary control data sequence can be transmitted in the rest of the VBI lines (e.g., VBI lines 7-25 and VBI lines 746-750), such as the sequence of control data (204) transmitted in VBI line 8 as depicted in FIG. 2.

[0027] It should be noted that the invention disclosed in this application is not limited to the VBI line numbering scheme as described above. A person of ordinary skill in the art can apply the principal of the invention to any other numbering scheme after reading the disclosure here.

[0028] According to some embodiments of this invention, the exact VBI line number for transmitting the equalization reference signal consisting of a single burst of sine wave does not need to be fixed but instead can be programmable. For example, a simple 5 bit data field in the control sequence can be used to define the VBI line number for this simple equalization reference signal. The downstream video receiver can determine which VBI line contains the simple equalization reference signal after decoding the control data. This scheme allows flexible use of a horizontal line of the VBI for transmitting a simple equalization reference signal thus can be easily adapted for different industry standards for digital video data transmission.

[0029] According to a preferred embodiment of this invention, the equalization reference signal of a single burst has the following characteristics: an amplitude preferably equal to about 75% of the amplitude of white color signal, a preferred frequency equal to the maximum frequency of the luminance bandwidth, a preferred burst or impulse width that approximately equals one horizontal line. It is noted that the preferred frequency of the single tone equalization signal is chosen to be approximately equal to the maximum frequency of the luminance bandwidth so that the receiver can use the reference signal to measure and compensate for the high frequency loss of the channel.

[0030] FIG. 3 illustrates a timing diagram of a single tone equalization reference signal transmitted during a horizontal line of a VBI according to one embodiment of the invention. As shown in FIG. 3, Chroma reference burst signal 304 is transmitted immediately after horizontal sync signal 302 during a horizontal line. The single tone equalization reference signal 306 follows the Chroma reference burst signal 304. Using the same example as shown in FIG. 2, the horizontal line of FIG. 3 corresponds to line 749 of FIG. 2 and reference signal 202 is now shown as single tone reference signal 306.

[0031] According to one further aspect of the invention, the Chroma reference burst signal 304 which is used as a reference phase for Chroma decoding can also be used for equalization purpose in applications where such a Chroma reference burst signal exists in all signal formats (color or black/white). As a high frequency burst of sine wave, this Chroma reference burst signal can be similarly utilized by the equalizer on the receiver side for purpose of downstream equalization just as the single burst equalization reference signal 306. Having a second equalization reference signal thus further improves the performance of the downstream equalization with minimal hardware cost.

[0032] FIG. 4 illustrates the transmission scheme of control data during a horizontal line of a VBI of a video signal according to a prior art. As shown in FIG. 4, after the horizontal sync (402) and the Chroma reference burst (404), there is a one-bit cell pulse (406) that signals the beginning of the transmission of control/protocol data. Each bit of the protocol data (408) takes the time period of 3 bit to transmit: the start bit “1”(410), the data bit (412) and the end bit “0”(414). This approach is very inefficient for utilizing the available VBI lines for transmission of various useful data. The more various control data transmitted during the VBI, the better improvement can be achieved for the communication between the encoder and the downstream receiver.

[0033] FIG. 5 illustrates the transmission of control data during a horizontal line of the VBI of a video signal according to one embodiment of the invention. In FIG. 5, after the start bit (506), a sequence of control data bits (508) is transmitted without unnecessarily using any encapsulating start bits and end bits. This aspect of the invention therefore increases the capacity of transmitting control data during a fixed VBI time period by almost three times. In some implementation, a start sequence (multiple bits) as opposed to a single bit can be used to signal the start of the control data.

[0034] It should be noted that in the above discussed embodiment, the protocol for the control sequence, the number of bits for the control data, the bit cell width and preamble are pre-defined for both transmitter/receiver to communicate properly. In an alternative implementation, a single end bit (not shown) is transmitted signaling to the downstream receiver (112) the end of the control sequence. This alternative implementation allows the flexibility of the length of the control data but at the expense of additional hardware at the receiver end such as a buffer and the end bit decoding circuitry.

[0035] In some embodiments, the composition of the control data information included in the control sequence is programmable. As discussed above, the VBI signal generator 104 generates the control data in response to host commands. Depending on the host commands, the control data information may consist of video format in some implementations and camera information in some other implementations, or both in yet some other implementations. Also, the frequency of the reference signal, the location within the VBI for the equalization reference signal, or any of the combinations of these and other different types of control information can be included in the control sequence depending on the host command.

[0036] FIG. 6 illustrates a flow chart of a method for sending an equalization reference signal and/or a control sequence during the VBI according to an embodiment of the invention. In FIG. 6, the digital VBI signal generator 104 optionally generates (604) a control sequence and then generates (606) an equalization reference signal of a predefined frequency. Based on the timing signal generated by the data/sync processor 102, Summer 106 combines the equalization reference pulse with the active video data in digital domain such that the transmission of the reference signal and the optionally generated control sequence data take place at a predetermined time period during the vertical blanking interval of the video signal. The D/A converter 108 then converts (610) the combined digital signal into an analog video transport signal. The converted analog transport signal is then transmitted (612) over transmission line 110 to downstream receiver 112.

[0037] In an alternative embodiment according to one aspect of the invention, only a control sequence is generated and no single tone reference signal is generated. The control sequence is combined with the digital video data in summer 106 in a scheme as discussed above with reference to FIG. 5.

[0038] Although the present invention has been particularly described with reference to the preferred embodiments thereof, it should be readily apparent to those of ordinary skill in the art that changes and modifications in the form and details may be made without departing from the spirit and scope of the invention. It is intended that the appended claims encompass such changes and modifications.