Method and apparatus for providing scalable pre-compressed digital video with reduced quantization based artifacts (continuation)

摘要

A method for generating a digital motion video sequence at a plurality of bit rates uses a transitional coding source when switching between bitstreams having different bit rates during transmission of a video sequence. The transitional data may be frames coded using reconstructed frames reconstructed for a first bitstream using the characteristics of the second bitstream. These “low bit rate insert frames,” or LBIFs, contain the image characteristics of a signal coded at the lower bit rate. With a bitstream having a higher bit rate being periodically coded using an LBIF, a point of image continuity between the two bitstreams is provided. Thus, switching from one bitstream to the other at this point in the video sequence minimizes the production of artifacts caused by differences in bit rate. In another embodiment of the invention, a separate set of transitional data is created, taking the form of “switch” frames, or S-frames. The S-frames are typically the difference between a frame of a first bitstream and a frame of a second bitstream. These frames are inserted into the decoded bitstream during the transition from one bitstream to the other, and compensate for any visual artifacts that might otherwise occur due to the difference in bit rate of the two bitstreams.