Data processing technique for limiting the bandwidth of data to be stored in a buffer

• US 5,463,422 A
• Filed: 10/13/1993
• Issued: 10/31/1995
• Est. Priority Date: 10/13/1993
• Status: Expired due to Term

• Current Assignee: Creative Technology Ltd.
• Original Assignee: Auravision Corporation
• Inventors: Gibson, Steven L., Simpson, Miles S., Kimura, Scott A.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US08/136,621
• Time in Patent Office: 748 Days
• Field of Search: 348/392, 348/406, 348/419, 348/424, 348/425, 348/552, 348/565, 348/568
• US Class Current: 348/390.1
• CPC Class Codes: G09G 2340/12 Overlay of images, i.e. displayed pixel being the result of switching between the corresponding input pixels
• CPC Class Codes: G09G 2340/125 wherein one of the images is motion video
• CPC Class Codes: G09G 5/393 Arrangements for updating the contents of the bit-mapped memory
• CPC Class Codes: G09G 5/395 Arrangements specially adapted for transferring the contents of the bit-mapped memory to the screen G09G5/399 takes precedence
• CPC Class Codes: H04N 19/00 Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
• CPC Class Codes: H04N 21/4143 embedded in a Personal Computer [PC]

Abstract

The bandwidth capability of a full-motion video buffer is prevented from being exceeded by automatically controlling the horizontal scaling of the incoming video data and the horizontal zooming or expansion of the outgoing display data to force the bandwidth of the video data to virtually match the bandwidth capability of the video buffer. In one embodiment, this automatic control of the horizontal scaling and zooming is performed in a dynamic fashion where a detector detects the dropping of any video bits caused by the bandwidth of the incoming video data exceeding the bandwidth capability of the video buffer. Upon detection of these dropped bits, the horizontal scaling of the incoming video data is incrementally reduced (and the horizontal zooming is proportionally increased) until the bandwidth of the incoming video data is at or below the maximum bandwidth capability of the memory buffer. In this way, the video buffer cannot be overdriven and no video data is lost. This technique also applies to processing non-video data.

Claims

1. A video processing method comprising the steps of:

applying pixel data having a first bandwidth to a horizontal scaler, said pixel data being for use in conjunction with a pixel array type display, said pixel data for controlling multiple rows of pixels in said display;

determining a substantially maximum bandwidth of a data buffer for storing said pixel data;

in response to said step of determining, controlling said horizontal scaler to reduce an amount of pixel data associated with each horizontal row of pixels in said display to reduce said first bandwidth of said pixel data to be at a second bandwidth which is at or below said maximum bandwidth of said data buffer;

storing resulting pixel data having said second bandwidth in said data buffer for subsequent display;

outputting pixel data from said data buffer; and

adding pixel data to said pixel data outputted from said data buffer to compensate for the reduction of pixel data during said step of controlling said horizontal scaler.

2. The method of claim 1 wherein said step of adding pixel data maintains a desired video window size on said display despite the extent of reduction of pixel data during said step of controlling said horizontal scaler.

3. The method of claim 1 wherein said step of controlling said horizontal scaler further comprises the steps of:

calculating a horizontal scaling factor necessary to reduce said first bandwidth of said pixel data to said second bandwidth; and

controlling said horizontal scaler in accordance with said horizontal scaling factor.

4. The method of claim 1 further comprising the steps of applying pixel data to a vertical scaler and controlling said vertical scaler to eliminate all pixel data associated with one or more rows of pixels in said display to reduce storage requirements of said data buffer.

5. The method of claim 1 wherein said data buffer is a DRAM.

6. The method of claim 1 wherein said data buffer is a VRAM.

7. The method of claim 1 wherein said step of determining a substantially maximum bandwidth of said data buffer comprises the steps of:

determining when a maximum bandwidth of said data buffer is exceeded by a bandwidth of said pixel data; and

controlling said horizontal scaler to reduce an amount of pixel data to reduce said bandwidth of said pixel data until said bandwidth of said pixel data is below said maximum bandwidth of said data buffer.

8. A video processing method comprising the steps of:

applying pixel data having a first bandwidth to a horizontal scaler, said pixel data being for use in conjunction with a pixel array type display, said pixel data for controlling multiple rows of pixels in said display;

sequentially storing pixel data in a first-in first-out (FIFO) buffer connected between a data buffer and said horizontal scaler;

determining when said FIFO buffer has an overflow of pixel data;

controlling said horizontal scaler to reduce an amount of pixel data to reduce a bandwidth of said pixel data until said FIFO buffer does not overflow;

storing resulting pixel data in said data buffer; and

outputting pixel data from said data buffer.

9. A video processing method comprising the steps of:

applying pixel data having a first bandwidth to a data buffer, said pixel data being for use in conjunction with a pixel array type display, said pixel data for controlling multiple rows of pixels in said display;

determining an output bandwidth of a data buffer necessary for enabling said data buffer to store said pixel data at said first bandwidth;

storing said pixel data having said first bandwidth in said data buffer for subsequent display;

outputting pixel data from said data buffer at an output bandwidth; and

in response to said step of determining, expanding said pixel data outputted from said data buffer to reduce a demand on said data buffer to output pixel data, said step of expanding pixel data causing said output bandwidth of said data buffer to be reduced to that necessary to enable said data buffer to store said pixel data at said first bandwidth.

10. The method of claim 9 wherein said step of expanding regenerates pixel data to maintain a desired video window size on said display.

11. The method of claim 9 wherein said step of determining an output bandwidth of said data buffer comprises the steps of:

determining when an input bandwidth of said data buffer is exceeded by said first bandwidth of said pixel data; and

regenerating additional pixel data for being displayed to reduce said demand on said data buffer until said data buffer is able to store said pixel data at said first bandwidth.

12. A data processing system comprising:

a data source providing a data stream having a first bandwidth;

a compressor connected to receive said data stream having said first bandwidth, said compressor being controllable to reduce a bandwidth of said data stream by reducing the number of bits in said data stream;

a data buffer connected to receive an output of said compressor for temporarily storing data outputted by said compressor, said data buffer having a maximum bandwidth for storing said data;

a first-in first-out (FIFO) buffer connected between said data buffer and said compressor;

a detector connected to said FIFO buffer to determine when said FIFO buffer has an overflow of data and, in response, providing an overflow signal to indicate that said data stream outputted by said compressor exceeds said maximum bandwidth of said data buffer; and

a controller connected to said compressor, said controller, in response to said overflow signal from said detector, causing said compressor to reduce a bandwidth of said data stream by reducing the number of bits in said data stream until said bandwidth of said data stream is equal to or less than said maximum bandwidth of said data buffer.

13. The system of claim 12 wherein said controller controls said compressor in response to said detector to progressively reduce the number of bits in said data stream to progressively reduce a bandwidth of said data until said FIFO buffer does not overflow.

14. The system of claim 12 further comprising a decompressor connected to an output of said data buffer for regenerating data to compensate for the reduction of bits by said compressor when reducing said bandwidth of said data stream.

15. The system of claim 12 wherein said data comprises pixel data for use in conjunction with a pixel array type display, said pixel data for controlling multiple rows of pixels in said display, and wherein said compressor is a horizontal scaler for reducing the amount of pixel data associated with each horizontal row of pixels in said display.