Patent Application
20090128708
1. Field of the Disclosure
The disclosed subject matter relates generally to instrumentation for monitoring the transmission quality of digital signals and, more particularly, digital multimedia content signals.
2. Description of the Related Art
Advanced Television Systems Committee (ATSC) standards define a digital standard for over the air TV reception in the United States. The development of the standard required a transmission (encoding) specification and a receiving (decoding) specification. In order to get the standard developed, the transmission specification, generally referred to as 8-level vestigial sideband (8VSB) modulation, was finalized first. After the transmission standard was established, the decoding side of the process started to evolve and so did the variety of decoder chip sets used in ATSC tuners. Currently there are five different generations of ATSC decoder chip sets. A consumer or commercial receiver may use any one of the five generations of chip sets.
In the following description, details are set forth by way of example to facilitate discussion of the disclosed subject matter. It should be apparent to a person of ordinary skill in the field, however, that the disclosed embodiments are exemplary and not exhaustive of all possible embodiments. Throughout this disclosure, a hyphenated form of a reference numeral refers to a specific instance of an element and the un-hyphenated form of the reference numeral refers to the element generically or collectively. Thus, for example, widget 102-1 refers to an instance of a widget class, which may be referred to collectively as widgets 102 and any one of which may be referred to generically as a widget 102.
In one aspect, a monitoring unit for use in monitoring and/or testing digital multimedia content signals is disclosed. The disclosed monitoring unit may include locally or remotely selectable functionality for decoding a multimedia content signal using any of a plurality of signal decoding algorithms. In some embodiments, the monitoring unit includes multiple chip sets where each chip set corresponds to a respective decoding algorithm or a respective version of a particular decoding algorithm and selection of the appropriate decoding algorithm is achieved by selection of the applicable chip set. In these embodiments, the selectable functionality allows a technician to analyze a signal using the same decoding algorithm as a device that is experiencing a problem to create a known baseline from which to troubleshoot. Having the ability to emulate a device beneficially facilitates the process of determining the device, the incoming signal, or both as the source of a problem. The ability to employ different versions of a decoding algorithm would also allow for making the wisest decision on equipment deployment by, for example, identifying geographic locations where older generation decoding algorithms may be adequate.
In another aspect, the disclosed monitoring unit includes an analysis module employing multiple algorithms for demodulating and analyzing a digital multimedia signal. The different algorithms may be selected, either remotely or locally, so that, at any time, the monitoring unit is using one of a multiple of decoding algorithms. In some embodiments, different decoding algorithms employed by the analyzer are implemented with corresponding chip sets so that, for example, a first decoding algorithm is implemented in a first chip set, a second decoding algorithm is implemented in a second chip set and so forth. In some embodiments, the disclosed monitoring unit may support two or more different generations or revisions of a demodulation specification. In embodiments suitable for use in conjunction with the terrestrial broadcasting of ATSC compliant multimedia signals, for example, the disclosed monitoring unit may include two or more selectable chip sets where each chip set implements an algorithm for demodulating an 8VSB modulated signal.
In some embodiments, the disclosed monitoring unit as implemented includes a chassis configured to receive two or more swappable decoding boards, where each decoding board includes a chip set and software/firmware to support a particular decoding algorithm, such as a particular revision of an 8VSB decoding algorithm. The chassis might further include a reception port for receiving a signal and a switch operable to connect the reception port to any of the selectable decoding boards currently installed in the chassis. Each decoding board may generate a decoded signal as an output and provide the decoded signal to an analysis module for determining one or more characteristics or parameters for the decoded signal. The chassis may also include a communications link. The communications link may communicate with a monitoring station. The communications link may, for example, communicate the decoding signal to the monitoring station or communicate a signal indicative of the output of the analysis of the demodulated signal. Thus, for example, the disclosed monitoring unit may decode a signal according to a selectable decoding algorithm and transmit the decoded signal to a monitoring station for analysis. In other embodiments, the decoded signal is provided to an analysis module within the monitoring unit for further analysis.
Before describing details of any particular embodiment, a description of an exemplary environment in which disclosed monitoring units may be used is presented. Referring to
Transmitter 107 may be a broadcast transmission tower or the like and multimedia signal 103 may be a broadcast quality, Advanced Television Systems Committee (ATSC) compliant multimedia signal. In other implementations, transmitter 107 may include elements or aspects of a national office, also sometimes referred to as a national headend, that delivers multimedia content to one or more regional offices including the depicted regional office 102. For implementations in which transmitter 107 represents a national headend, multimedia signal 103 may be transmitted over a fiber optic backbone or other suitable high bandwidth medium to regional office 102.
Although
As depicted in
In some embodiments, multimedia signal 103 as received by regional office 102 corresponds to a single item of multimedia content, e.g., a single show or a single video-on-demand title. In these embodiments, regional office 102 may aggregate a number of such signals and transmit multimedia signal 103 as part of a composite multimedia signal (not depicted explicitly) that includes multiple shows and/or movies. In such cases, receiver 104 may be responsible for selectively processing the desired multimedia signal by filtering the composite multimedia signal as transmitted by regional office 102. In a coaxial based system, for example, in which regional office 102 transmits all or substantially all available channels of multimedia content to the end user simultaneously, the desired multimedia signal 103 may correspond to particular frequency band and receiver 104 may be operable as a tuner that selects multimedia signal 103 from the composite signal.
Multimedia signal 103 may be an encoded signal in which the multimedia content is formatted according to a predetermined protocol or specification. In some embodiments, for example, multimedia content stream may be encoded according to a pervasive encoding protocol such as MPEG 2 or the like. In some embodiments, multimedia signal 103 may be broadcast transmitted to receiver 104 from regional office 102 or directly from the broadcaster (not depicted). In other embodiments, regional office 102 delivers multimedia signal 103 to receiver(s) 104 over a wired access network, which may have a physical medium implemented with twisted copper cable, coaxial cable, fiber optic cable, any combination thereof, or a suitable alternative.
As shown in
Referring now to
Referring to
Because each byte of multimedia signal 103 is important to both the identification of the proper channel selected by a user and the content to ultimately be displayed to the user, lost data, whether lost in transmission to receiver 104 or during delivery to transmitter 107, will degrade the signal delivered to the subscriber or other end user and the user may not be able to view selected content satisfactorily. Historically, an operator of a transmission system often became aware such errors were occurring only after an error or problem was reported by an end user, at which time the operator would initiate corrective action.
Monitoring unit 106 may monitor the transmission subsystem and the reception subsystem for a multimedia signal, since error can occur at either location. Monitoring unit 106 may monitor and diagnose errors resulting from the signal transmission or receiver equipment as well as errors resulting from geographical or environmental disturbances, including weather related disturbances. In order to monitor and diagnose errors, monitoring unit 106 may analyze either a real time or recorded broadcast channel to find a non-functioning channel, which may be one that plays no content, the wrong content, audio and video content out of synch, etc. To quantify the quality of an incoming signal, monitoring unit 106 may monitor parameters including packet error rate for decoding the signal into packets; the signal-to-noise ratio after equalization and phase correction, at the point where the signal goes into a decoder; and the tap coefficients and total tap energy from the equalization stage; and may analyze the syntax of the transport packets; the percentage of the transport stream used by various data types, channels, and elementary streams; and the accuracy, jitter, and transmission frequency of the Program Clock References.
Circuit boards 405 are disposed within chassis 403, in parallel, and in such a manner as to be electrically isolated from one another, using brackets 409. Circuit boards 405 may be secured to brackets 409 using a friction fit, adhesive, screw means, or similar means. One skilled in the art will appreciate that depending upon the materials used to fabricate chassis 403, brackets 409, removable panel 407, and the attachment means for all of these, and whether chassis 409 is to be installed in an outdoor location, it may be necessary to electrically isolate circuit boards 405 using, for example, a resin coating.
In some embodiments, circuit boards 405 are operable as decoding boards capable of decoding encoded multimedia signals. In the depicted embodiment, for example, each circuit board 405 includes a corresponding chip set 406. Chip sets 406 may be implemented as single chip or multiple chip decoders that include hardware, firmware, and software to demodulate and otherwise decode multimedia signals. In other embodiments, the decoding functionality of chip sets 406 may be implemented entirely or primarily in software. In some embodiments, for example, chip sets 406 are operable to demodulate an MPEG-2 compliant multimedia stream that has been modulated using 8VSB modulation. In some embodiments, each chip set 406 supports or uses a corresponding demodulation algorithm. In embodiments of monitoring unit 106 dedicated to multimedia signals that are modulated using 8VSB modulation, each chip set 406 may correspond to a different revision of an 8VSB demodulation specification. More generally, each circuit board 405 in monitoring unit 106 may include a corresponding decoder unit operable to decode a multimedia signal.
Circuit boards 405 may be implemented using commercially distributed electronic components for analyzing signals. Examples of such circuit boards include the MPM 400 model of boards sold by Tektronix, Inc., and past and future generations of the same. When each circuit board 405 corresponds to a different decoding algorithm, monitoring unit 106 as shown achieves integration of several different generations of monitoring units, each employing different chipsets to demodulate digital signals, in one monitoring unit.
The general operation of monitoring unit 106 will now be described with reference to
Each circuit board 405 contained within the chassis 403 of monitoring unit 106 may directly tap into the multimedia signal output to the receivers 104, or may in the alternative be connected to another control circuit that further directs the signals incoming to and outgoing from monitoring unit 106.
Referring now to
Multimedia signal receiver 505 is operable to receive a broadcast multimedia signal such as multimedia signal 103 (
For simplicity, the above description contemplates a monitoring unit 106 in which the circuit boards 405 are selected individually either manually such as by user input interface 510 or remotely by a user at the monitoring station. In other embodiments, microprocessor 501 may be operable to select the circuit board 405 automatically.
In use, monitoring unit 106 may be continuously monitoring outgoing television signals for multiple channels of content using multiple chip sets with different processing capabilities, i.e., it is demodulating and processing the data packets for each output channel using chipsets corresponding to multiple generations of receivers. To do this, a particular circuit board 405 is either automatically selected or selected by a user as described above. The circuit board then outputs appropriate monitoring or diagnostic signals to the station and the next circuit board is queried. When a new chipset is delivered to market, the operator removes the top portion of the monitoring unit and either expands the number of boards, or replaces a board already contained therein. The monitoring unit is then reset, i.e., the maximum number of circuit boards, time to query each board, etc., and the monitoring unit resumes monitoring the digital signal. In this way, monitoring unit 106 is capable of changing and expanding to test digital signals according to the capabilities of different generations of chipsets.
One skilled in the art will appreciate the monitoring units on the circuit boards as disclosed herein will retain much of their previous functionality and accordingly may also be used to analyze recorded signals or signals supplied by various receivers. Moreover, although the subject matter has been described with reference to a certain embodiment, this description is not meant to be construed in a limiting sense. On the contrary, various modifications of the disclosed embodiment will become apparent to those skilled in the art upon reference to the detailed description. It is therefore contemplated that the appended claims will cover such modifications, alternatives, and equivalents that fall within the spirit and the scope of the claimed subject matter. Thus, to the maximum extent allowed by law, the scope of the present disclosure is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.
