Systems and methods for decoding of partially corrupted reversible variable length code (RVLC) intra-coded macroblocks and partial block decoding of corrupted macroblocks in a video decoder
View Patent ↗The invention is related to methods and apparatus that recover usable video data from partially corrupted data. Embodiments inspect corrupted data packets and identify the location or locations of an error, whether the corrupted data packet contains data expected to be error-free, and whether the error-free data should be used. Decoding of a packet in both the forward direction and the backward direction can be used to locate a position of an error. Intra-coded macroblocks can also be recovered. A decoder can elect to use or to drop an intra-coded macroblock recovered from a corrupted data packet according to further criteria that is applied to the recovered intra-coded macroblock. One embodiment inspects video bitstream data that has been encoded with an optional data partitioning feature enabled, and retrieves specified data in areas of a corrupted packet that are expected to be free from error.
1. A circuit adapted to recover useful data from a video packet that is at least partially corrupted, the circuit comprising: a decoding circuit configured to decode a video packet in a forward direction and in a backward direction, where the decoding circuit detects bit locations of errors first encountered in the forward direction and in the backward direction; a counter adapted to maintain a count of complete macroblocks decoded in the forward direction and in the backward direction; and a control circuit adapted to discard at least a portion of the video packet that corresponds to an overlapping region, where the control circuit is further configured to further discard additional data corresponding to a backtracking amount when there is no overlapping region, where the control circuit is further configured to discard information in incomplete macroblocks, and where the control circuit is adapted to permit use of at least a portion of the remaining data.
2. The circuit as defined in claim 1 , wherein the backtracking amount is 90 bits in each direction.
3. The circuit as defined in claim 1 , wherein the control circuit is further configured to discard an intra-coded macroblock from a partially corrupted video packet.
4. The circuit as defined in claim 1 , further comprising a ring buffer, which stores a video bitstream and is coupled to the decoding circuit such that the decoding circuit can access a video packet in both the forward direction and in the backward direction.
5. A circuit adapted to recover useful data from a video packet that is at least partially corrupted, the circuit comprising: a data parsing circuit adapted to determine whether a video packet is encoded with data partitioning enabled; an error checking circuit configured to determine whether an error exists ahead of a motion marker of the video packet; and a decoder coupled to the data parsing circuit and to the error checking circuit, where the decoder is adapted to decode at least a portion of the data in the corrupted video packet ahead of the motion marker when data parsing circuit indicates that the video packet is encoded with data partitioning enabled and when the error checking circuit indicates that the error does not exist ahead of the motion marker.
6. The circuit as defined in claim 5 , wherein the error checking circuit further comprises: a prediction circuit that generates a predicted location for the motion marker; a circuit that detects an actual location of the motion marker; and a comparison circuit that indicates that the error exists ahead of the motion marker when the actual location and the predicted location do not match.
7. A circuit adapted to recover useful data from a video packet that is at least partially corrupted, the circuit comprising: means for receiving the video packet; means for ending without recovering data when corruption is detected in at least one of a video packet header of the video packet, a DC portion of the video packet, and a motion vector portion of the video packet; means for initiating decoding of the video packet in a forward direction; means for maintaining a first count of a number of macroblocks decoded without error in the forward direction; means for storing codewords decoded in the forward direction; means for storing a first bit location when an error is first detected in the forward direction; means for initiating decoding of the video packet in a reverse direction; means for maintaining a second count of a number of macroblocks decoded without error in the reverse direction; means for storing codewords decoded in the reverse direction; means for storing a second bit location when an error is first detected in the reverse direction; means for determining if there is an overlapping region, where the overlapping region corresponds to a region identified in both the forward direction and in the reverse direction as having an error; means for discarding the data in the overlapping region and for using the data in a remaining portion of the video packet if there is an overlapping region; and means for discarding the data between a first backtracking amount ahead of the first error location in the forward direction and a second backtracking amount behind the second error location in the first location, and for recovering the remaining portion of the video packet if there is no overlapping region.