Video decoder architecture and method for using same

• US 20020122491A1
• Filed: 04/06/2001
• Published: 09/05/2002
• Est. Priority Date: 01/03/2001
• Status: Abandoned Application

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Karczewicz, Marta, Kurceren, Ragip
• Application Number:
  US09/827,796
• Publication Number:
  US 20020122491A1
• Time in Patent Office: Days
• US Class Current: 375/240.25
• CPC Class Codes: H04N 19/105 Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
• CPC Class Codes: H04N 19/164 Feedback from the receiver or from the transmission channel
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/39 involving multiple description coding [MDC], i.e. with separate layers being structured as independently decodable descriptions of input picture data
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/58 Motion compensation with long-term prediction, i.e. the reference frame for a current frame not being the temporally closest one H04N19/23 takes precedence
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/65 using error resilience
• CPC Class Codes: H04N 19/89 involving methods or arrangements for detection of transmission errors at the decoder
• CPC Class Codes: H04N 21/23424 involving splicing one content stream with another content stream, e.g. for inserting or substituting an advertisement
• CPC Class Codes: H04N 21/4384 involving operations to reduce the access time, e.g. fast-tuning for reducing channel switching latency
• CPC Class Codes: H04N 21/44016 involving splicing one content stream with another content stream, e.g. for substituting a video clip
• CPC Class Codes: H04N 21/64792 Controlling the complexity of the content stream, e.g. by dropping packets intermediate media network packet handling H04L65/765; proxy provisioning conversion or adaptation for reducing the amount or size of exchanged application data H04L67/5651; negotiation of resources in wireless networks H04W28/16

Abstract

A decoder and method for using a new picture or frame type is provided. This type is referred to an SP-picture. The temporal redundancies are not exploited in I-frames, compression efficiency of I-frame coding is significantly lower than the predictive coding. A method allows use of motion compensated predictive coding to exploit temporal redundancy in the sequence while still allowing perfect reconstruction of the frame using different reference frames. Methods using this new picture type provide for error resilience/recovery, bandwidth scalability, bitstream switching, processing scalability, random access and other functions.

The SP-type picture provides for, among other functions, switching between different bitstreams, random access, fast forward and fast error-recovery by replacing I-pictures to increase the coding efficiency. As will be demonstrated, SP-pictures have the property that identical SP-frames may be obtained even when they are predicted using different reference frames.

Claims

1. A decoder for decoding encoded data wherein identical frames may be obtained even when they are predicted using different reference frames, said decoder comprising:

means for forming a prediction of a current block of data using a plurality of motion vectors and a reference frame;

means for calculating a plurality of transform coefficients for said current block of data corresponding to a set of basis functions;

means for quantizing said coefficients creating a plurality of quantized prediction image coefficients;

means for obtaining a plurality of quantized reconstruction image coefficients by adding said received quantized coefficients for the prediction error to said plurality of quantized prediction image coefficients; and

means for dequantizing said plurality of quantized reconstruction image coefficients.

2. A decoder for decoding a block of encoded data wherein identical frames may be obtained even when they are predicted using different reference frames, said decoder comprising:

frame memory for storing a reference frame;

demultiplexor for receiving and demultiplexing said encoded data into motion information and a current frame;

motion compensation predictor coupled to said demultiplexor and said frame memory for receiving said motion information and constructing a prediction of the current block based on said motion information and reference frame;

transformer coupled to said motion compensation predictor for creating a plurality of transform coefficients;

quantisationizer coupled to said transformer for quantizing said plurality of coefficients; and

adder coupled to said quantisationizer and said demultiplexor for adding current frame information and said quantized plurality of coefficients to form a reconstructed frame.

3. The decoder of claim 2, further comprising:

inverse quantizationizer coupled to said adder; and

inverse transformer coupled to said inverse quantizationizer.

4. A method for encoding a frame of video data, comprising the steps of:

forming a prediction of a current block of data using a plurality of motion vectors and a reference frame;

calculating a plurality of transform coefficients for said current block of data corresponding to a set of basis functions;

quantizing said coefficients creating a plurality of quantized prediction image coefficients;

obtaining a plurality of quantized reconstruction image coefficients by adding said received quantized coefficients for the prediction error to said plurality of quantized prediction image coefficients; and

dequantizing said plurality of quantized reconstruction image coefficients.

5. A method for switching between a plurality of bitstreams in a data communication system, wherein said bitstreams correspond to a same data sequence but are encoded at different bitrates, said method comprising the steps of:

placing a first picture within each of said plurality of bitstreams in locations at which switching from one of said plurality of bitstreams to another one of said plurality of bitstreams is desired;

transmitting a second picture wherein said first picture and said second picture are represented by different bitstreams, but wherein said first picture and said second picture reconstructed values are identical.

6. A method for enabling access in a data stream, said method comprising the steps of:

placing a plurality of SP-pictures at fixed intervals within a first bitstream;

generating an I-picture and an SP-picture for each one of said plurality of SP-pictures in said first bitstream;

storing said I-picture in a second bitstream at a temporal location preceding said each one of said plurality of SP-pictures in said first bitstream; and

storing said SP-picture in said second bitstream at same temporal locations as each of said SP-pictures in said first bitstream.

7. The method of claim 6, wherein said second bitstream comprises only SP-pictures predicted from each other, but at longer temporal periods.

8. A method for providing Video Redundancy Coding (VRC), comprising the steps of:

dividing a sequence of pictures into a plurality of threads wherein all pictures are assigned to one of said plurality of threads in a round-robin fashion;

coding each of said plurality of threads independently;

creating a frame, wherein all of said threads converge; and

starting a second plurality of threads from said frame.

9. A method for providing error control in a data stream between a sender and a client in a communication system, said method comprising:

creating a plurality of representations of a frame in the form of a plurality of SP-pictures predicted from different reference pictures;

signaling said sender information regarding lost frames and a one of said plurality of representations received by said client; and

sending said client a SP-picture which is the next picture in said one of plurality of representations received by client.