Adjusting Program Clock References for Wireless Video Stability
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Solution Overview
Problem
Publicly accessible communication networks, such as the Internet, experience high jitter and latency, leading to buffer overflow or underflow issues in multimedia content delivery, resulting in poor video and audio quality due to the variability in data packet arrival times and throughput.
Innovation Solution
The use of Program Clock References (PCRs) to adjust transmission parameters and pacing of video frames, ensuring stable data throughput and buffer management by modifying PCRs based on network latency and roundtrip delay, thereby maintaining high-quality video and audio output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If data packets are transmitted over publicly accessible communication networks, then network accessibility and versatility are improved, but jitter and latency increase causing buffer overflow or underflow
Solution Approach 1:
The patent applies preliminary action by pre-calculating and inserting adjusted Program Clock References (PCRs) into video frames before transmission. The adjusting module computes corrected PCRs based on measured network latency and jitter characteristics in advance, so that when packets arrive with variable delays, the decoder can still reconstruct the program clock accurately without buffer overflow or underflow
Solution Approach 2:
The patent implements feedback by measuring actual network latency and roundtrip delay, then using this measured information to adjust subsequent PCRs. The system continuously monitors network conditions and dynamically modifies PCR values to compensate for observed jitter, creating a closed-loop control system that adapts to changing network conditions
2Reliability
If transmission pacing is increased to maintain buffer stability, then buffer overflow is prevented, but video frame rate and playback smoothness deteriorate
Solution Approach 1:
The patent changes the temporal parameter of PCR values to compensate for network jitter without altering the actual video frame rate. By adjusting the clock reference timestamps rather than the transmission timing of frames, the system maintains both buffer stability and playback smoothness simultaneously
Solution Approach 2:
The adjusted PCR acts as an intermediary between the variable network transmission and the decoder's buffer management. Instead of directly controlling transmission pacing, the system uses modified clock references as an intermediate mechanism to inform the decoder about expected arrival times, allowing the decoder to proactively manage its buffer
3Measurement precision
If PCRs are adjusted based on network latency, then clock reconstruction accuracy is improved, but computational complexity and processing overhead increase
Solution Approach 1:
The patent replaces complex real-time transmission control mechanisms with a simpler timestamp adjustment approach. Instead of dynamically controlling packet transmission timing based on network conditions, the system substitutes this with pre-calculated PCR adjustments that achieve the same clock synchronization goal with less computational overhead
Data Source
AI summary
Processing a video stream using upon Program Clock References (PCRs) contained therein in preparation for transmission to a wireless device. Operation includes receiving video frames of the video stream, buffering the video frames, and extracting PCRs from at least some of the video frames of the video stream. Operation further includes, based upon at least the values of the PCRs, determining transmission parameters, and transmitting video frames of the video stream to the wireless device according to the transmission parameters. Operation may further include determining a round trip delay of transmissions to the wireless device and acknowledgements from the wireless device, adjusting PCRs of at least some video frames of the video stream based upon the round trip delay, and transmitting the video frames of the video stream to the wireless device.