Delay Equalizer for IP Media Stream Synchronization
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Solution Overview
Problem
In the transition from SDI to IP for media and entertainment, existing techniques fail to synchronize video and audio streams effectively without introducing undesirable latency, as IP switches are not designed to hold video or audio frames, leading to potential data duplication and quality degradation.
Innovation Solution
A network element with an ingress port, egress port, and delay equalizer is used to receive data packets with source-provided time stamps, compute delays for synchronization, and send delay messages to each source, ensuring packets are synchronized across multiple stream sources, including audio, video, and meta-data streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If IP streams are switched by an IP switch, then bandwidth efficiency is improved, but synchronization capability deteriorates since holding video frames or audio samples is not what an IP switch is designed for
Solution Approach 1:
The patent introduces a timing message generator as an intermediary component that works in conjunction with the IP switch. This generator creates timing messages based on received data packets and sends them to output ports, enabling synchronization without requiring the IP switch itself to hold or buffer video frames or audio samples. The intermediary handles the timing coordination while the IP switch maintains its high-speed packet forwarding capability.
2Reliability
If a receiver-based flow switch is used, then synchronization is achieved, but bandwidth is doubled since both current flow and new flow need to be sent to the receiver
Solution Approach 1:
The system performs preliminary timing analysis by examining received data packets and generating appropriate timing messages before data is forwarded. The timing message generator pre-calculates the timing adjustments needed based on packet arrival times and sends timing information ahead of or alongside data packets, allowing receivers to synchronize without requiring duplicate data flows.
Solution Approach 2:
The system implements feedback by having the timing message generator continuously monitor packet arrival times at the ingress port and adjust timing messages accordingly. This feedback loop ensures that timing information reflects actual network conditions and packet flow patterns, enabling dynamic synchronization adjustment without increasing bandwidth requirements.
3Reliability
If video frames or audio samples are held for synchronization, then stream alignment is improved, but latency is introduced
Solution Approach 1:
The patent replaces the mechanical approach of physically holding or buffering video frames and audio samples with an information-based approach. Instead of time-consuming buffering operations, the system uses timing messages that carry synchronization information, allowing receivers to align streams through software-based timestamp adjustment rather than physical data retention.
Data Source
AI summary
A method including providing a network element including an ingress port, an egress port, and a delay equalizer, providing an equalization message generator, receiving, at the ingress port, a plurality of data packets from multiple sources, each data packet having a source indication and a source-provided time stamp, determining, at the ingress port, a received time stamp for at least some of the received data packets, passing the received data packets, the source-provided time stamps, and the received time stamps to the delay equalizer, the delay equalizer computing, for each source, a delay for synchronizing that source with other sources, the equalization message generator receiving an output, for each source, including the delay for that source, from the delay equalizer and producing a delay message instructing each source regarding the delay for that source, and sending, from the egress port, the delay message to each source. Related apparatus is also provided.