Concurrent discrete time oscillators (DTO) for video and closed caption encoding

• US 6,256,070 B1
• Filed: 10/13/1998
• Issued: 07/03/2001
• Est. Priority Date: 08/03/1998
• Status: Expired due to Term

• Current Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Original Assignee: ATI International SRL (Advanced Micro Devices, Inc.)
• Inventors: Frank, Michael
• Primary Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US09/170,519
• Time in Patent Office: 994 Days
• Field of Search: H04/N.708, H04/N.974, 348/468, 348/473, 348/475, 348/589, 348/600, 348/469, 348/486
• US Class Current: 348/473
• CPC Class Codes: H04N 7/0885 for the transmission of subtitles
• CPC Class Codes: H04N 9/641 Multi-purpose receivers, e.g. for auxiliary information H04N9/642 takes precedence

Abstract

A video encoding system combines the processing of image data and closed caption data in the formation of a raster television signal. By combining the processing of image data and closed caption data, a single discrete time oscillator (DTO) can be used to generate oscillation signals that are required for each process. In a preferred embodiment, the DTO generates the 500 kHz signal that is used as the “run in” clock for closed caption data, and also generates the subcarrier signal that is used for the modulation of the chrominance components of a composite video signal.

Claims

1. A video encoding system comprising:

a video encoder that concurrently receives and processes image data and closed caption data to generate raster encoded sample data corresponding to at least one video sampling phase of a plurality of video sampling phases;

a digital to analog converter, operably coupled to the video encoder, that receives and converts the raster encoded sample data to an analog video and closed caption raster signal; and

a synchronization control module, operably coupled to the digital to analog converter, that receives and mixes the analog video and closed caption raster signal with other raster signals to produce a raster television signal.

2. The video encoding system of claim 1, wherein the video encoder further comprises a discrete time oscillator that receives a clock signal and generates a first phase value during a first period of the clock signal and a second phase value during a second period of the clock signal to facilitate the concurrent processing of image data and closed caption data.

3. The video encoding system of claim 2, wherein the first phase value corresponds to the at least one video sampling phase, and the second phase value corresponds to at least one closed caption sampling phase.

4. The video encoding system of claim 3, wherein the video encoder further comprises a sine cosine generator that generates sine factors and cosine factors of a subcarrier signal and generates oscillation samples corresponding to a clock run in signal.

5. The video encoding system of claim 4, wherein the video encoder further comprises:

a plurality of multipliers, wherein at least one of the plurality of multipliers multiplies a chrominance component of the image data with at least one of the sine factors; and

wherein at least another one of the plurality of multipliers multiplies another chrominance component of the image data with at least one of the cosine factors to produce a quadrature-phase modulation product.

6. The video encoding system of claim 5, wherein the video encoder further comprises:

a plurality of adders, wherein at least one of the plurality of adders sums the quadrature-phase modulation product from the plurality of multiplier to produce a quadrature-phase modulated chrominance signal; and

wherein at least another one of the plurality of adders sums a luminance component of the image data with the quadrature-phase modulated chrominance signal to produce a video composite sample data.

7. The video encoding system of claim 6, wherein the video encoder further comprises a timing controller that generates the clock signal and synchronizes the generation of the sine factor and cosine factor corresponding to a phase of the subcarrier signal relative to a sample rate of the image data.

8. The video encoding system of claim 7, wherein the video encoder further comprises:

a plurality of multiplexers, wherein at least one of the plurality of multiplexers selects and receives a specified number of the oscillation samples, samples of closed captioned data, and control signals from the timing controller to generate closed caption sample data corresponding to the at least one closed caption sampling phase of a plurality of closed caption sampling phases; and

another one of the plurality of multiplexers receives the video composite sample data, the closed caption sample data, and control signals from the timing controller to generate the raster encoded sample data.

9. The video encoding system of claim 8 further comprises at least one sample of the closed caption sample data that corresponds to an oscillation sample of the clock run in signal.

10. The video encoding system of claim 8 further comprises at least one sample of the closed caption sample data that corresponds to a sample of the closed captioned data taken at the sample rate of the image data.

11. The video encoding system of claim 8 further comprises a multiplexer which replaces the video composite sample data with the closed caption sample data at each time period corresponding to lines 21 and 284 in the raster encoded sample data.

12. The video encoding system of claim 4, wherein the sine cosine generator further comprises a quadrature generator, operably coupled to the discrete time oscillator, that receives the first phase value, the second phase value, and sine and cosine values to generate a quadrature value and a phase angle.

13. The video encoding system of claim 9, wherein the sine cosine generator further comprises a factor memory that contains a plurality of factor values.

14. The video encoding system of claim 13, wherein the sine cosine generator further comprises a table lookup module, operably coupled to the quadrature generator and the factor memory, that:

selects a video factor value of the plurality of factor values based on the at least one video sampling phase;

selects a closed caption factor value of the plurality of factor values based on the at least one closed caption sampling phase; and

generates the sine factor and cosine factor.

15. The video encoding system of claim 14 wherein the raster encoded sample data is based upon the video factor value.

16. The video encoding system of claim 14 wherein the closed caption sample data is based upon the closed caption factor value.

17. A method for video encoding, the method comprises the steps of:

a) concurrently receiving image data and closed caption data;

b) concurrently processing the image data and the closed caption data to generate raster encoded sample data corresponding to at least one video sampling phase of a plurality of video sampling phases;

c) converting the raster encoded sample data to an analog video and closed caption raster signal; and

d) mixing the analog video and closed caption raster signal with other raster signals to produce a raster television signal.

18. The method of claim 17, wherein the step of concurrently processing further comprises:

generating sine factors and cosine factors of a subcarrier signal; and

generating oscillation samples corresponding to a clock run in signal based on the concurrently received image data and closed caption data.

19. The method of claim 18, wherein the step of concurrently processing further comprises:

multiplying a chrominance component of the image data with at least one of the sine factors; and

multiplying another chrominance component of the image data with at least one of the cosine factors to produce a quadrature-phase modulation product.

20. The method of claim 19, wherein the step of concurrently processing further comprises:

summing the quadrature-phase modulation product to produce a quadrature-phase modulated chrominance signal; and

summing a luminance component of the image data with the quadrature-phase modulated chrominance signal to produce a video composite sample data.

21. The method of claim 20, wherein the step of concurrently processing further comprises:

selecting and receiving a specified number of the oscillation samples, samples of closed captioned data, and control signals from a timing controller to generate closed caption sample data corresponding to at least one closed caption sampling phase of a plurality of closed caption sampling phases; and

receiving the video composite sample data, the closed caption sample data, and control signals from the timing controller to generate the raster encoded sample data.

22. The method of claim 21, wherein the step of concurrently processing further comprises generating a first phase value during a first period of the clock signal, and a second phase value during a second period of the clock signal, such that the first phase value corresponds to the at least one video sampling phase, and the second phase value corresponds to the at least one closed caption sampling phase.

23. The method of claim 22, wherein the step of concurrently processing further comprises receiving the first phase value, the second phase value, and sine and cosine values to generate a quadrature value and a phase angle.

24. The method of claim 21, wherein the step of concurrently processing further comprises:

selecting a video factor value of a plurality of factor values based on the at least one video sampling phase;

selecting a closed caption factor value of the plurality of factor values based on the at least one closed caption sampling phase; and

generating the sine factor and cosine factor.

25. The method of claim 19, wherein the step of concurrently processing further comprises:

generating a clock signal; and

synchronizing the generation of the sine factor and cosine factor corresponding to a phase of the subcarrier signal relative to a sample rate of the image data.