Video Decoder Adaptive Bit Rejection for Error Resilience
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Solution Overview
Problem
Existing video decoders face challenges in handling bit errors in video bitstreams due to variable length coding, leading to loss of synchronization, error propagation, and poor picture quality, as they either discard too much valid data or retain erroneous information.
Innovation Solution
The solution involves dynamically rejecting a variable number of bits before an error detection point in the video bitstream based on the average bits per macroblock in previously decoded slices, using the formula BitsToBeRejected=THm*Max[ACS, APS], where THm is a constant specific to the video coding standard and entropy coding mode, to minimize the discard of good data while addressing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If video decoders discard all bits before the error detection point, then error propagation is avoided, but valid data is lost resulting in poor picture quality
Solution Approach 1:
Instead of discarding all bits back to the last resynchronization marker (excessive action), the patent applies partial action by rejecting only a calculated number of bits based on the formula BitsToBeRejected=THm*Max[ACS, APS]. This partial rejection approach removes only the suspected corrupted bits while preserving valid bits that were incorrectly retained by prior art methods.
Solution Approach 2:
The patent changes the parameter of bit rejection quantity from fixed (all bits or zero bits) to variable based on content characteristics. By calculating the average number of bits per macroblock (ACS and APS) and using this to determine the rejection quantity, the system adapts the action to the specific content being decoded, optimizing the balance between error removal and data preservation.
2Loss of information
If video decoders retain all bits before the error detection point, then valid data is preserved, but erroneous data is retained causing error propagation
Solution Approach 1:
The patent applies partial rejection action rather than complete retention. By calculating and rejecting a specific number of bits (BitsToBeRejected=THm*Max[ACS, APS]), the system removes the erroneous portion while preserving the valid portion, avoiding the extreme of retaining all bits including corrupted ones.
Solution Approach 2:
The system uses feedback from error detection to adjust the decoding process. When an error is detected, the system calculates the average bits per macroblock from previously decoded error-free slices and uses this feedback information to determine how many bits to reject from the current erroneous slice, creating a adaptive error handling mechanism.
3Reliability
If more resynchronization markers are inserted to control slice size, then bit error impact is reduced, but decoding complexity increases
Solution Approach 1:
Instead of changing the structural parameter of slice division (number of RMs per frame), the patent changes the handling parameter of error recovery. By modifying the bit rejection strategy based on content characteristics (ACS and APS calculations), the system achieves better error resilience without altering the fundamental decoding structure or increasing complexity.
Data Source
AI summary
A method of video decoding discards a context dependent number of bits following detection of an invalid symbol. In the preferred embodiment the number of discarded bits depends upon the product of a constant corresponding to the video encoding standard and the current slice type and the maximum of the average number of bits per macroblock of the current slice and a stored average number of bits per macroblock of a previous slice of the same coding type.