Dual Video Stream Switching for Fast Channel Change Synchronization
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Solution Overview
Problem
Digital A/V apparatuses experience significant channel change delays due to the GOP structure and processing components, particularly because of the need for intra-coded frames and de-jittering, which can lead to synchronization issues between audio and video content during channel changes.
Innovation Solution
The method involves receiving and processing dual video streams with different characteristics, such as shorter GOP size and lower resolution, and introducing a delay in the secondary stream to reduce buffering latency, ensuring synchronization by switching between the streams during channel changes, utilizing a digital audio and video apparatus with specific processing and buffering means.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If buffering process is used to reduce audio jitter, then audio quality is improved, but channel change time increases and audio-video synchronization is lost
Solution Approach 1:
The patent divides the video stream into two separate streams with different characteristics: a first video stream with longer GOP size and higher quality, and a second video stream with shorter GOP size and lower quality. The audio stream is processed separately with de-jittering buffering. This segmentation allows the system to use the second video stream for faster channel changes while the audio stream maintains its quality through buffering, resolving the contradiction between audio quality and channel change speed.
Solution Approach 2:
The patent changes the GOP structure parameters of the video stream by creating two versions: one with longer GOP intervals for normal playback and one with shorter GOP intervals for rapid channel changing. By dynamically switching between these parameter configurations based on user behavior, the system achieves both fast channel changes and maintains audio-video synchronization without compromising audio quality.
2Reliability
If de-jittering buffering is applied to audio content, then audio synchronization is improved, but channel change delay increases
Solution Approach 1:
The patent prepares the second video stream in advance with a shorter GOP structure, so that when channel changing is needed, immediately decodable video frames are already available. This preliminary preparation of the alternative video stream eliminates the need to wait for I-frames during channel changes, reducing delay while the audio de-jittering buffer continues to operate normally.
Solution Approach 2:
The patent introduces a second video stream as an intermediary solution during channel changes. This intermediary stream acts as a bridge, providing decodable video content while the audio stream completes its de-jittering process. The system switches to this intermediary video stream temporarily during channel changes, allowing audio and video to resynchronize without the full channel change delay.
3Loss of energy
If I frames are encoded less frequently to reduce bit rate, then transmission efficiency is improved, but channel change delay increases
Solution Approach 1:
The patent segments the video encoding strategy into two modes: normal mode with infrequent I-frames for energy efficiency, and channel change mode with frequent I-frames for speed. By maintaining two separate video streams with different encoding characteristics, the system achieves low bit rate during normal operation while enabling fast channel changes when needed.
Solution Approach 2:
The patent makes the video stream dynamic by switching between two pre-configured streams based on operational mode. The system dynamically selects the appropriate video stream configuration (long GOP for normal playback, short GOP for channel changes) rather than using a fixed encoding structure, thereby optimizing both bit rate efficiency and channel change performance.
Data Source
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AI summary
A digital A/V apparatus (50) provides reduced channel changes times and maintains synchronization between audio and video content during a channel change event. According to an exemplary embodiment, the digital A/V apparatus (50) includes at least one signal receiver (52, 62) for receiving a first audio stream, a first video stream and a second video stream, wherein the first and second video streams represent the same program and the first video stream has at least one characteristic different from the second video stream; a first audio signal processor (68) for processing the first audio stream to generate a first processed audio stream; a first video signal processor (66) for processing the first video stream to generate a first processed video stream; a second video signal processor (56, 58) for processing the second video stream to generate a second processed video stream having a delay with respect to the first processed video stream; a first buffer (74) for buffering the first processed audio stream to provide de-jittering; a renderer (78, 80) for rendering the first processed audio stream and the second processed video stream in response to a channel change command; a switch (76) for switching from the second processed video stream to the first processed video stream after the renderer (78) begins rendering the second processed video stream, and thereby causing the renderer (78) to begin rendering the first processed video stream; and whereby synchronization between the first processed audio stream and the first processed video stream is maintained during a channel change event.