Method and apparatus for video underflow detection in a raster engine
View Patent ↗An improved raster engine adapted to render video data from a frame buffer to one of a plurality of disparate displays is disclosed which comprises apparatus for detecting one or more video underflow conditions. The raster engine includes a first in first out (FIFO) memory, which obtains video data from a frame buffer and provides video data to a video pipeline, along with input and output counters associated with the FIFO memory. A control logic system is associated with the FIFO memory and adapted to provide an underflow indication according to the input and output counter values. A method for detecting video underflow in a video controller raster engine is also disclosed. The method includes obtaining an input counter value indicative of video data obtained from the frame buffer and an output counter value indicative of video data provided from a memory to a video pipeline in the raster engine, performing a comparison of the input and output counter values, and selectively providing an underflow indication according to the input and output counter value comparison.
1. A video controller raster engine for receiving video data from a frame buffer and rendering formatted data to a display in a computer system, the raster engine comprising:
a first in first out (FIFO) memory that interfaces a host bus in the computer system with the raster engine, obtains interleaved first and second video data from the frame buffer via the host bus and provides the interleaved video data to a video pipeline;
a control logic system associated with the FIFO memory and which evaluates first input and output counter values, and second input and output counter values, respectively associated with the first and second video data, and provides at least one of an existing video data underflow indication and an imminent underflow indication based at least in part on one of the first input and output counter values and the second input and output counter values.
2. The raster engine of claim 1 , the first input counter has a first input counter value indicative of video data obtained from the frame buffer, and the first output counter has a first output counter value indicative of video data provided to the video pipeline.
3. The raster engine of claim 2 , the second input counter has a second input counter value indicative of video data obtained from the frame buffer, and the second output counter has a second output counter value indicative of video data provided to the video pipeline.
4. The raster engine of claim 3 , the raster engine selectively performs a dual scan operation with the FIFO memory providing the interleaved first and second video data to the video pipeline, represented by first and second output counter values.
5. The raster engine of claim 4 , the control logic system provides the underflow indication based at least in part on the first input and output counter values and second input and output counter values.
6. The raster engine of claim 1 , the underflow indication comprises an underflow signal indicative of at least one of an existing underflow condition, an anticipated underflow condition, and a raster engine lockup condition.
7. The raster engine of claim 6 , the control logic system provides the underflow signal to a host processor in the computer system.
8. The raster engine of claim 6 , the underflow signal indicates one of an existing underflow condition and an anticipated underflow condition when the first input and output counter values are within a threshold value of each other.
9. The raster engine of claim 8 , the raster engine comprises an underflow threshold value register programmable by a host processor in the computer system, and the control logic system obtains the threshold value from the threshold value register, and compares the threshold value with the difference between the first input and output counter values.
10. The raster engine of claim 8 , the underflow signal indicates an existing underflow condition when the first input and output counter values are equal, and an anticipated underflow condition when the first input and output counter values are within a threshold value of each other.
11. A method of detecting underflow conditions in a video controller raster engine, comprising:
providing interleaved first and second video data from a FIFO memory to a video pipeline;
evaluating first input and output counter values, and second input and output counter values respectively associated with the first and second video data;
selectively performing a dual scan operation on the video data; and
providing an underflow indication based at least in part on one of the first input and output counter values and the second input and output counter values.
12. The method of claim 11 , further comprising providing interleaved first and second video data to the video pipeline represented by the first and second output counter values.
13. The method of claim 11 , the underflow indication indicates at least one of an existing underflow condition, an imminent underflow condition, and a raster engine lockup condition.
14. The method of claim 13 , the underflow indication indicates an existing or imminent underflow condition when the first input and output counter values are within a threshold value of each other.
15. The method of claim 14 , further comprising comparing the difference of the first input counter value and the first output counter value to the threshold value to determine whether the first input and output counter values are within the threshold value of each other.
16. The method of claim 14 , the underflow indication indicates an existing underflow condition when the first input and output counter values are equal, and an imminent underflow condition when the first input and output counter values are within the threshold value of each other.
17. The method of claim 13 , the underflow indication indicates an existing or imminent underflow condition when the second input and output counter values are within a threshold value of each other.
18. The method of claim 17 , further comprising comparing the difference of the second input counter value and the first output counter value to the threshold value to determine whether the second input and output counter values are within the threshold value of each other.
19. The method of claim 17 , the underflow indication indicates an existing underflow condition when the second input and output counter values are equal, and an imminent underflow condition when the second input and output counter values are within the threshold value of each other.
20. A system for detecting underflow conditions in a video controller raster engine, comprising:
means for providing interleaved first and second video data from a FIFO memory to a video pipeline;
means for evaluating first input and output counter values, and second input and output counter values, respectively associated with the first and second video data;
means for selectively performing a dual scan operation on the video data; and
means for indicating at least one of an existing underflow condition and an imminent underflow condition based at least in part on one of the first input and output counter values and the second input and output counter values.