Video Telephony Bitrate Transition I-Picture Request
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Solution Overview
Problem
During video telephony sessions, especially in high-definition video telephony, the transition from a higher to a lower bitrate can result in a period of poor or no video quality due to the flushing of intra-coded pictures from the decoder's buffer, leading to a delay in receiving new I-pictures, which diminishes user experience.
Innovation Solution
Implementing a request for a second intra-coded picture through RTCP messages, such as a picture loss indication (PLI) or full intra request (FIR), in response to detecting a change in bitrate or buffer flushing, to ensure timely receipt of new I-pictures and maintain video quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the bitrate is changed from higher to lower during video telephony, then bandwidth consumption is reduced, but video quality deteriorates due to flushing of intra-coded pictures from buffer
Solution Approach 1:
The system sends a request for a second intra-coded picture immediately when bitrate change is detected, before the buffer is completely flushed. This preliminary action ensures that a replacement I-picture is already in transit or being decoded, minimizing the period of poor video quality that would otherwise occur while waiting for the next I-picture from the remote encoder.
Solution Approach 2:
The system implements feedback by monitoring bitrate changes and buffer status, then automatically triggering requests for additional intra-coded pictures. This closed-loop control ensures that video quality is maintained during bitrate transitions by dynamically adjusting the frequency of I-picture requests based on actual buffer conditions and bitrate changes.
2Quantity of substance
If intra-coded pictures are flushed from buffer during bitrate change, then decoder memory is freed, but video display quality deteriorates due to lack of reference pictures
Solution Approach 1:
The system requests a second intra-coded picture immediately upon detecting bitrate change, before the buffer flush completes. This ensures that reference pictures are replenished in advance, maintaining video display quality while still allowing the buffer to be freed for the bitrate transition.
Solution Approach 2:
The system changes the parameter of I-picture request frequency dynamically - sending requests more frequently during bitrate transitions when buffer flushing occurs, and returning to normal operation after stabilization. This parameter adjustment ensures buffer memory is available when needed while maintaining video quality during critical transition periods.
3Device complexity
If the system waits for natural I-picture generation after bitrate change, then encoding complexity is reduced, but time delay increases due to poor video quality period
Solution Approach 1:
The system sends a request for the second intra-coded picture immediately when bitrate change is detected, rather than waiting for the remote encoder to naturally generate the next I-picture. This preliminary action reduces the time delay and period of poor video quality, while the request mechanism itself adds minimal encoding complexity compared to waiting for natural I-picture generation.
Data Source
AI summary
An apparatus configured for video telephony includes a receiving device configured to receive video data at a first bitrate; send a request to change the first bitrate to a second bitrate; receive a first intra coded picture in response to the request to change the first bitrate to the second bitrate; in response to detecting the second bitrate, flush the first intra coded picture from a picture buffer; and in response to flushing the first intra coded picture from the picture buffer, send a request for a second intra coded picture.