Claims
- 1. An apparatus for converting a compressed bitstream, comprising:a demultiplexer to extract each of a plurality of video objects from a compressed input bitstream as an elementary input bitstream having a first bit rate; a transcoder to convert each elementary input bitstream to an elementary output bitstream having a second bit rate; a transcoding control unit, coupled to the transcoder, to generate control information for the transcoder; and a multiplexer configured to compose the elementary output bitstreams into a compressed output bitstream having the second bit rate.
- 2. The apparatus of claim 1 wherein the second bit rate is less than the first bit rate.
- 3. The apparatus of claim 1 further comprising:an output buffer, coupled to the multiplexer, to generate rate feedback information for the transcoding control unit.
- 4. The apparatus of claim 1 wherein the transcoder converts multiple elementary bit streams in parallel.
- 5. The apparatus of claim 1 wherein the transcoding control unit further comprises a shape analyzer, a texture analyzer, a temporal analyzer, and a spatial analyzer to generate the control information from object data generated by the transcoder.
- 6. The apparatus of claim 5 wherein the texture analyzer uses a texture model R=S·(X1Q+X2Q2)where R represents a number of texture bits spent for a particular video object (VO), Q represents a quantization parameter QP, X1 and X2 represent the first and second-order model parameters, and S represent a encoding complexity.
- 7. The apparatus of claim 6 wherein the texture model is updated by linear regression using results from previous n frames.
- 8. The apparatus of claim 6 wherein the encoding complexity S is defined by a discrete cosine transform-based complexity measure {tilde over (S)}: S~=1MC∑m∈M∑i=163 ρ(i)·&LeftBracketingBar;Bm(i)&RightBracketingBar;2where Bm(i) are AC coefficients of a block, m is a block index in a set M of coded blocks, MC is the number of blocks in the set M, and ρ(i) is a frequency dependent weighting.
- 9. The apparatus of claim 6 wherein the texture model is updated before and after converting a particular video object.
- 10. The apparatus of claim 1 wherein a first temporal quality of a first video object at a given instant in time is different than a second temporal quality of a second video object at the given instant in time.
- 11. The apparatus of claim 1 wherein a first spatial quality of a first video object at a given instant in time is different than a second spatial quality of a second video object at the given instant in time.
- 12. The apparatus of claim 1 wherein each elementary bitstream is converted independent of other elementary bitstreams.
- 13. The apparatus of claim 1 wherein the transcoder further comprises:a video object layer/video object plane parser, a shape scaler, a header parser, a motion parser, a texture scaler, a bitstream memory connected to each other by a bitstream bus.
- 14. The apparatus of claim 1 wherein the video object layer/video object plane parser determines whether a particular video object includes shape information.
- 15. The apparatus of claim 13 wherein the shape scaler further comprises:a shape decoder/parser, a shape down-sampler, and a shape encoder serially connected to each other.
- 16. The apparatus of claim 15 wherein shape information of the video objects is converted by the down-sampler.
- 17. The apparatus of claim 13 wherein the texture scaler further comprises:a partial texture decoder, a texture down-sampler, a coded bit pattern re-compute unit, a coefficient memory, and a quantizer to generate a variable length code for the bitstream memory.
- 18. The apparatus of claim 17 wherein a previous variable bit length code in a header of a particular elementary bitstream is replaced by the variable bit length code generated by the texture scaler.
- 19. The apparatus of claim 17 wherein the texture down-sampler operates in a discrete cosine transform domain.
- 20. The apparatus of claim 5 wherein the transcoder includes a texture scaler including a quantizer to quantize the video objects according to a quantization parameter generated by the texture analyzer.
- 21. A method for converting a compressed bitstream, comprising the steps of:extracting each of a plurality of video objects as an elementary input bitstream having a first bit rate from a compressed input bitstream; converting each elementary input bitstream to an elementary output bitstream having a second bit rate; generating control information for the converting; and composing the elementary output bitstreams into a compressed output bitstream having the second bit rate.
- 22. The method of claim 21 wherein the second bit rate is less than the first bit rate.
- 23. The method of claim 1 further comprising the steps of:generating rate feedback from an output buffer.
- 24. The method of claim 1 wherein the control information is generated by analyzing shape, texture, time, and space data of the video objects.
- 25. The method of claim 24 wherein the texture analyzing uses a texture model R=S·(X1Q+X2Q2)where R represents a number of texture bits spent for a particular video object (VO), Q represents a quantization parameter QP, X1 and X2 represent the first and second-order model parameters, and S represents an encoding complexity.
- 26. The method of claim 25 wherein the texture model is updated by linear regression using results from previous n frames.
- 27. The method of claim 25 wherein the encoding complexity S is defined by a discrete cosine transform-based complexity measure {tilde over (S)}: S~=1MC∑m∈M∑i=163 ρ(i)·&LeftBracketingBar;Bm(i)&RightBracketingBar;2where Bm(i) are AC coefficients of a block, m is a block index in a set M of coded blocks, MC is the number of blocks in the set M, and ρ(i) is a frequency dependent weighting.
- 28. The method of claim 25 wherein the texture model is updated before and after converting a particular video object.
- 29. The method of claim 21 wherein a first temporal quality of a first video object at a given instant in time is different than a second temporal quality of a second video object at the given instant in time.
- 30. The method of claim 21 wherein a first spatial quality of a first video object at a given instant in time is different than a second spatial quality of a second video object at the given instant in time.
- 31. The method of claim 21 wherein multiple elementary bitstreams are converted in parallel.
CROSS-REFERENCE TO RELATED APPLICATION
This is a Continuation-in Part Application of U.S. Patent Application of U.S. patent application Ser. No. 09/496,706, “Adaptable Compressed Bitstream Transcoder” filed,” filed on Feb. 2, 2000 by Vetro et al.
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Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
09/496706 |
Feb 2000 |
US |
Child |
09/504323 |
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US |