Frame timing synchronization for an inline scaler using multiple buffer thresholds

A graphics system comprising:

• a display generation unit configured to:
• generate image frames having a resolution of horizontal pixels per vertical pixels (HVP), and wherein each image frame comprises a plurality of lines;
• provide the image frames as a data stream for display;
• a scaler unit configured to:
• receive the data stream;
• obtain a scaled data stream by scaling the received data stream according to a scaling ratio, wherein the scaled data stream comprises scaled image frames, and each scaled image frame comprises scaled lines;
• generate evenly spaced output pixel valid pulses according to the scaling ratio;
• and
• sequentially output the scaled lines by outputting each subsequent scaled line of the scaled lines on a corresponding subsequent output pixel valid pulse of the output pixel valid pulses;
• a buffer configured to store the scaled lines, wherein the scaler unit is configured to sequentially output the scaled lines from the buffer;
• and
• a threshold lookup table configured to store a specified number of threshold values determined according to the scaling ratio, wherein the scaler unit is further configured to generate the output pixel valid pulses according to the stored specified number of threshold values;
• wherein the scaler unit is configured to generate a next respective one of the output pixel valid pulses responsive to receiving an indication from the buffer that an occupancy of the buffer has reached a value corresponding to one of the specified number of threshold values.

A method for timing scaled image frames, the method comprising:

• receiving, in a first clock domain, input frame streams comprising horizontal input lines of pixel data;
• scaling the received pixel data, said scaling producing corresponding output frame streams comprising horizontal output lines of pixel data;
• outputting the output frame streams in a second clock domain, comprising:
• for each output frame stream of the output frame streams, subsequent to outputting each horizontal output line of the horizontal output lines in the output frame stream, waiting for a same specified time duration before outputting a next horizontal output line of the horizontal output lines in the output frame stream;
• the method further comprising:
• storing the horizontal output lines in a buffer, wherein said outputting the output frame streams comprises outputting the horizontal output lines from the buffer;
• storing a specified number of threshold values in a lookup table;
• receiving an occupancy value from the buffer;
• and
• for each output frame stream of the output frame streams:
• selecting a next stored horizontal output line of the output frame stream from the buffer:
• retrieving from the lookup table a respective threshold value corresponding to the next stored horizontal output line;
• and
• outputting the next stored horizontal output line from the buffer, responsive to the received occupancy value reaching the respective threshold value.