Video Frame Rate Conversion for Interlaced Displays
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Solution Overview
Problem
Existing methods fail to properly display DVD titles with different frame formats, such as NTSC and PAL, on display systems with different vertical refresh rates, leading to issues with resolution and continuity of motion.
Innovation Solution
A method and apparatus that decodes video, converts frame sizes, and controls output to match the display system's frame rate, using a decoder, filter, memory, and controller to resize and sequence frames according to the target display system's format, ensuring proper interlaced display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If frame size is modified to suit interlaced display system, then display compatibility is improved, but resolution is lost
Solution Approach 1:
The video signal is segmented into separate even and odd fields, with even field lines displayed during even field intervals and odd field lines during odd field intervals. This field-based segmentation allows the system to maintain high resolution while adapting to interlaced display requirements by processing and displaying half the lines at a time at higher refresh rates.
Solution Approach 2:
The system dynamically adjusts the scanning process by varying the vertical refresh rate to match different display systems (59.94 Hz for NTSC, 50 Hz for PAL) while maintaining the original frame resolution. The encoder/decoder dynamically switches between different field assignment strategies based on the target display format.
2Adaptability or versatility
If vertical refresh rate is changed to match display system, then display compatibility is improved, but continuity of motion is disrupted
Solution Approach 1:
The system uses periodic field doubling or field repetition techniques where original fields are periodically repeated or synthesized to match the display system's refresh rate. This periodic action maintains the illusion of continuous motion by providing regularly spaced visual updates that match the display's temporal characteristics.
Solution Approach 2:
A field converter acts as an intermediary between the source video signal and the display system, transforming the temporal characteristics of the video signal to match the display's refresh rate while preserving the visual continuity. This intermediary performs field assignment and timing synchronization to bridge the gap between different refresh rates.
3Adaptability or versatility
If frame rate is altered to match display system, then display compatibility is improved, but motion smoothness deteriorates
Solution Approach 1:
The encoder performs preliminary field assignment and timing synchronization before video playback, pre-processing the video signal to anticipate the display system's refresh rate requirements. This preliminary action ensures that fields are properly prepared and assigned in advance, maintaining motion smoothness during actual playback without requiring real-time conversion.
Solution Approach 2:
The system changes temporal parameters (field timing, vertical refresh rate) while maintaining spatial parameters (resolution, frame size) constant. By selectively modifying only the necessary temporal parameters and using field-based processing, the system adapts to different display refresh rates while preserving motion smoothness through proper field sequencing and timing.
Data Source
AI summary
An apparatus for displaying a motion video on a display system includes a decoder for decoding the motion video to provide a decoded picture, the decoded picture having a first frame size and a first scan rate different from a second frame size and a second scan rate of the display system, respectively, a filter for converting the decoded picture into an intermediate picture, and then converting the intermediate picture into a resized frame picture having the second frame size, a memory for storing resized frame pictures sent from the filter, and a controller for controlling output of the resized frame pictures from the memory in a sequence by assigning the resized frame pictures over successive field time intervals in accordance with the ratio between the first scan rate and the second scan rate.