Methods and apparatus to test receivers

1. A method of testing receiver video fidelity, wherein the receiver includes a decoder, a display rate converter, and an output, the method comprising:

producing a video test signal;

transforming the video test signal to include direct current terms and alternating current terms;

nulling values of the alternating current terms of the video test signal;

communicating the video test signal including the null values of the alternating current terms and the direct current terms to an input of the receiver; and

measuring signal characteristics of signals provided at the receiver output.

2. A method as defined by claim 1 , wherein producing the video test signal comprises recalling the video test signal from storage.

3. A method as defined by claim 1 , wherein producing the video test signal includes:

converting the video test signal including the direct current terms and the nulled alternating current terms into a format compatible with the input of the receiver.

4. A method as defined by claim 1 , wherein transforming the video test signal to include the direct current terms and the alternating current terms includes performing a discrete cosine transformation.

5. A method as defined by claim 1 , wherein the video test signal is configured to cause the decoder to output a step function signal upon processing the video test signal.

6. A method as defined by claim 3 , wherein converting the video test signal includes multiplexing, applying conditional access, modulating, error correcting, or upconverting.

7. A method as defined in claim 5 , further comprising coupling the step function signal to the display rate converter.

8. A method as defined by claim 1 , further comprising comparing the measured signal characteristics of the output signals to reference data indicating acceptable measured signal characteristics.

9. A method as defined by claim 1 , wherein the measured signal characteristics at the output include one or more of signal risetime and signal overshoot.

10. A method as defined by claim 9 , wherein when the risetime measured signal characteristic is longer than risetime specified in the reference data, the receiver video fidelity is determined to be unacceptable.

11. A system for testing receiver video fidelity, wherein the receiver includes a decoder, a display rate converter, and an output, the system comprising:

a block detector to receive a video signal and detect video blocks therein;

a transformer to transform the detected video blocks into direct current coefficients and alternating current coefficients;

a coefficient nuller to null values of the alternating current coefficients, wherein

the nulled values of the alternating current coefficients and the direct current coefficients are included in a video test signal to be provided to the receiver; and

a measurement device to measure signal characteristics of signals provided at the receiver output.

12. A system as defined by claim 11 , wherein the transformer performs a discrete cosine transformation on the detected video blocks.

13. A system as defined by claim 11 , further comprising a converter to convert the nulled values of the alternating current coefficients and the direct current coefficient into the video test signal to be provided to the receiver, the converter comprising:

an encoder to encode the nulled alternating current coefficients and the direct current coefficients into a transport signal;

a modulator and forward error corrector for processing the transport signal; and

an uplink frequency converter to upconvert the processed transport signal.

14. A system as defined by claim 11 , wherein the measurement device compares the measured signal characteristics of the output signals to reference data indicating acceptable measured signal characteristics.

15. A system as defined by claim 11 , wherein the measured signal characteristics include one or more of signal risetime and signal overshoot.

16. A system as defined by claim 15 , wherein when the risetime measured signal characteristic is longer than a risetime specified in the reference data, the system indicates that the receiver video fidelity is unacceptable.

17. An article of manufacture comprising a machine-accessible medium having a plurality of machine accessible instructions that, when executed, cause a machine to test receiver video fidelity, wherein the receiver includes a decoder, a display rate converter, and an output, wherein the instructions cause the machine to:

produce a video test signal;

transform the video test signal to include direct current terms and alternating current terms;

null values of the alternating current terms of the video test signal;

communicate the video test signal including the null values of the alternating current terms and the direct current terms to an input of the receiver; and

measure signal characteristics of signals provided at the receiver output.

18. A machine-accessible medium as defined by claim 17 having instructions stored thereon that, when executed, cause a machine to produce the video test signal by recalling the video test signal from storage.

19. A machine-accessible medium as defined by claim 17 having instructions stored thereon that, when executed, cause a machine to produce the video test signal by

converting the video test signal including the direct current terms and the nulled alternating current terms into a format compatible with the input of the receiver.

20. A machine-accessible medium as defined by claim 17 having instructions stored thereon that, when executed, cause a machine to transform the video signal to include nulling the direct current terms and the alternating current terms by performing a discrete cosine transformation.