Selective Speech Frame FEC for Packet Loss Protection
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Solution Overview
Problem
Existing digital voice communication systems over packet-switched networks face degradation in speech quality due to packet loss, with conventional forward error correction (FEC) methods increasing bandwidth and delay, and receiver-based methods failing to effectively mask important frame losses.
Innovation Solution
A source and channel-controlled FEC scheme that selectively encodes and transmits critical speech frames, creating a redundant copy only when necessary, to maintain high speech quality without additional delay and at moderate data rates, adaptable to channel conditions and compatible with legacy devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional forward error correction (FEC) methods are used to protect speech frames, then speech quality is improved, but bandwidth consumption and transmission delay increase
Solution Approach 1:
The patent applies local quality by selectively protecting only critical speech frames rather than all frames uniformly. The system identifies frames containing important speech information (such as unvoiced frames or frames with significant spectral changes) and applies FEC redundancy only to these critical frames, while non-critical frames are transmitted without redundancy. This localized protection strategy maintains speech quality for important content while significantly reducing overall bandwidth consumption compared to protecting all frames.
Solution Approach 2:
The patent implements partial action by transmitting only a portion of the speech frames with FEC protection rather than providing excessive protection for all frames. The system determines the minimum necessary redundancy for critical frames based on their importance, avoiding the waste of bandwidth that would result from protecting every frame with full FEC. This partial protection approach achieves acceptable speech quality with moderate data rates.
2Reliability
If conventional forward error correction (FEC) methods are used to protect speech frames, then speech quality is improved, but transmission delay increases
Solution Approach 1:
By applying FEC protection only to critical speech frames rather than all frames, the patent reduces the overall processing and transmission time. Critical frames that require protection are identified and handled with FEC, while non-critical frames are transmitted immediately without redundancy processing. This selective approach minimizes the time loss associated with FEC operations while maintaining speech quality for important content.
3Quantity of substance
If receiver-based packet loss concealment is used, then bandwidth consumption is reduced, but speech quality degradation occurs when important frames are lost
Solution Approach 1:
The patent applies preliminary action by proactively transmitting FEC-protected redundant copies of critical speech frames before packet loss can occur. Instead of waiting for packet loss and then attempting concealment at the receiver, the system prepares and transmits protection data in advance for frames identified as critical. This preemptive approach ensures that when packet loss does occur, the receiver has pre-sent redundancy available to reconstruct the lost critical frames, maintaining speech quality without requiring excessive bandwidth.
4Reliability
If all speech frames are encoded with FEC to prevent packet loss, then speech quality is maintained, but data rate increases significantly
Solution Approach 1:
The patent implements local quality by applying different encoding strategies to different speech frames based on their criticality. Critical frames (those containing important speech information) are encoded with FEC redundancy, while non-critical frames are transmitted without FEC or with minimal protection. This differentiated approach maintains speech quality for important content while keeping the overall data rate at moderate levels, avoiding the significant bandwidth increase that would result from encoding all frames with FEC.
Data Source
AI summary
A method for preventing the loss of information within a speech frame is described. A first speech frame to be encoded is selected. A determination is made as to whether or not a second speech frame is a critical speech frame based on the information within the second speech frame and one or more adjacent speech frames. At least a part of an encoded version of the second speech frame is created according to a selected forward error correction (FEC) mode if the second speech frame is a critical speech frame. The first speech frame and the at least a part of the encoded version of the second speech frame are transmitted.