Systems and methods for encoding redundant motion vectors in compressed video bitstreams
The invention is related to methods and apparatus that encode redundant motion vectors for predictive-coded visual object planes (P-VOPs) to increase the robustness of transmitted video signals. One embodiment provides the redundant motion vectors in a user data video packet of an MPEG-4 compliant bitstream, which thereby allows the enhanced bitstream to remain compliant with MPEG-4 syntax and backwards compatible with MPEG-4 decoders. The enhanced bitstreams allow a video decoder to display a video with a better picture and relatively less error and error propagation when portions of the bitstream are disturbed or corrupted by interference, delays, and the like.
1. A process of providing a redundant motion vectors in an encoded video bitstream, the process comprising: receiving a plurality of video frames to be encoded; determining whether to encode a video frame as an Intra-coded frame (I-frame) or as a Predictive-coded frame (P-frame); when encoding a P-frame: encoding a first video object in the frame as a first predictive video object plane (P-VOP); determining whether the first P-VOP is related to a second VOP in a video frame at least two video frames prior to the P-frame that is being encoded; and computing a redundant motion vector that references motion for the first P-VOP based on the second VOP.
2. The process as defined in claim 1 , further comprising storing the redundant motion vector in a user data video packet such that the encoded video bitstream is compliant with standard MPEG-4 syntax.
3. The process as defined in claim 2 , further comprising storing a header extension code in the user data video packet.
4. The process as defined in claim 1 , further comprising storing the redundant motion vector in a user data video packet that immediately follows a data packet corresponding to the first P-VOP in the bitstream.
5. The process as defined in claim 1 , wherein the second VOP that is used as a reference for the redundant motion vector is from a video frame that is two frames prior to the P-frame that is being encoded.
6. The process as defined in claim 1 , further comprising: selecting a video frame the video frames that are at least two video frames prior to the P-frame that is being encoded, where the selected video frame is related to the P-frame that is being encoded; selecting the second VOP from the selected video frame; and providing an indication of the selected video frame in the encoded video bitstream.
7. The process as defined in claim 1 , further comprising automatically encoding at least two I-frames consecutively when encoding a frame as an I-frame.
8. The process as defined in claim 1 , wherein the determining whether to encode a video frame as an I-frame comprises detecting a scene change, further comprising: encoding the video frame corresponding to the scene change as an I-frame; and automatically encoding a video frame subsequent to the video frame that corresponds to the scene change as a scene change.
9. The process as defined in claim 1 , wherein the determining whether to encode a video frame as an I-frame comprises detecting a rapidly changing scene, further comprising: encoding the video frame corresponding to the rapidly changing scene as an I-frame; and automatically encoding a video frame subsequent to the video frame that corresponds to the rapidly changing as a scene change.
10. The process as defined in claim 1 , further comprising wirelessly transmitting the encoded video bitstream such that the encoded video bitstream can be received by at least one remote video decoder.