Encoder, Decoder and Methods for Encoding and Decoding Data Segments Representing a Time-Domain Data Stream

• US 20100138218A1
• Filed: 12/07/2007
• Published: 06/03/2010
• Est. Priority Date: 12/12/2006
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Geiger, Ralf
• Granted Patent: US 8,818,796 B2
• Time in Patent Office: Days
• US Class Current: 704/205
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/18 Vocoders using multiple modes
• CPC Class Codes: G10L 19/265 Pre-filtering, e.g. high frequency emphasis prior to encoding
• CPC Class Codes: H04N 19/00 Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
• CPC Class Codes: H04N 21/2368 Multiplexing of audio and video streams
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/2662 Controlling the complexity of the video stream, e.g. by scaling the resolution or bitrate of the video stream based on the client capabilities
• CPC Class Codes: H04N 21/4341 Demultiplexing of audio and video streams
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002

Abstract

An apparatus for decoding data segments representing a time-domain data stream, a data segment being encoded in the time domain or in the frequency domain, a data segment being encoded in the frequency domain having successive blocks of data representing successive and overlapping blocks of time-domain data samples. The apparatus includes a time-domain decoder for decoding a data segment being encoded in the time domain and a processor for processing the data segment being encoded in the frequency domain and output data of the time-domain decoder to obtain overlapping time-domain data blocks. The apparatus further includes an overlap/add-combiner for combining the overlapping time-domain data blocks to obtain a decoded data segment of the time-domain data stream.

Claims

1. An apparatus for decoding data segments representing a time-domain data stream, a data segment being encoded in the time domain or in the frequency domain, a data segment being encoded in the frequency domain comprising successive blocks of data representing successive and overlapping blocks of time-domain data samples, wherein two consecutive time-domain data blocks of which one being encoded in the frequency domain and one being encoded in the time domain comprising a time domain overlapping region, the apparatus comprising:

a time-domain decoder for decoding a data segment being encoded in the time domain to acquire output data of the time-domain decoder;

a processor for processing the data segments being encoded in the frequency domain and the output data of the time-domain decoder to acquire overlapping time-domain data blocks for the time domain overlapping region; and

an overlap/add-combiner for combining the overlapping time-domain data blocks in the time domain overlapping region to acquire a decoded data segment of the time-domain data stream for the time domain overlapping region.

2. The apparatus of claim 1, wherein the processor comprises a frequency-domain decoder for decoding data segments being encoded in the frequency domain to acquire frequency-domain data segments.

3. The apparatus of claim 1, wherein the processor is adapted for processing a data segment being encoded in the time domain and in the frequency domain in parallel.

4. The apparatus of claim 2, wherein the processor comprises a time-domain to frequency-domain converter for converting the output data of the time-domain decoder to acquire converted frequency-domain data segments.

5. The apparatus of claim 4, wherein the processor comprises a frequency-domain combiner for combining the frequency-domain data segments and the converted frequency-domain data segments to acquire a frequency-domain data stream.

6. The apparatus of claim 5, wherein the processor comprises a frequency-domain to time-domain converter for converting the frequency-domain data stream to overlapping time-domain data blocks.

7. The apparatus of claim 2, wherein the frequency domain decoder further comprises a re-quantization stage.

8. The apparatus of claim 4, wherein the time-domain to frequency-domain converter comprises a cosine modulated filterbank, an extended lapped transform, a low-delay filterbank, a polyphase filterbank or a modified discrete cosine transform.

9. The apparatus of claim 5, wherein the frequency-domain combiner comprises an adder.

10. The apparatus of claim 6, wherein the frequency-domain to time-domain converter comprises a cosine modulated filterbank or an inverse modified discrete cosine transform.

11. The apparatus of claim 1, wherein the time-domain decoder is adapted for using a prediction filter to decode a data segment encoded in the time domain.

12. The apparatus of claim 1, wherein the processor comprises a calculator for calculating overlapping time-domain data blocks based on the output data of the time-domain decoder.

13. The apparatus of claim 12, wherein the calculator is adapted for reproducing an overlapping property of the frequency-domain to time-domain converter based on the output data of the time-domain decoder.

14. The apparatus of claim 13, wherein the calculator is adapted for reproducing a time-domain aliasing characteristic of the frequency-domain to time-domain converter based on the output data of the time-domain decoder.

15. The apparatus of claim 6, wherein the frequency-domain to time-domain converter is adapted for converting the frequency-domain data segments provided by the frequency-domain decoder to overlapping time-domain data blocks.

16. The apparatus of claim 15, wherein the overlap/add-combiner is adapted for combining the overlapping time-domain data blocks provided by the frequency-domain to time-domain converter and the calculator to acquire decoded data segments of the time-domain data stream.

17. The apparatus of claim 8, wherein the calculator comprises a time-domain aliasing stage for time-aliasing output data of the time-domain decoder to acquire the overlapping time-domain data blocks.

18. The apparatus of claim 12, wherein the calculator is adapted for

segmenting the output of the time-domain decoder in calculator segments comprising 2N sequential samples,

applying weights to the 2N samples according to an analysis window function,

subtracting the first N/2 samples in reversed order from the second N/2 samples,

adding the last N/2 samples in reversed order to third N/2 samples,

inverting the second and third N/2 samples

replacing the first N/2 samples with the time-reversed and inverted version of the second N/2 samples,

replacing the fourth N/2 samples with the time-reversed version of the third N/2 samples, and

applying weights to the 2/N samples according to a synthesis windowing function.

19. The apparatus of claim 6, wherein the overlap/add-combiner is adapted for applying weights according to a synthesis windowing function to overlapping time-domain data blocks provided by the frequency-domain to time-domain converter.

20. The apparatus of claim 19, wherein the overlap/add-combiner is adapted for applying weights according to a synthesis windowing function being adapted to a size of an overlapping region of consecutive overlapping time-domain data blocks.

21. The apparatus of claim 20, wherein the calculator is adapted for applying weights to the 2N samples according to an analysis windowing function being adapted to a size of an overlapping region of consecutive overlapping time-domain data blocks and wherein the calculator is adapted for applying weights to the 2N samples according to a synthesis windowing function being adapted to the size of the overlapping region.

22. The apparatus of claim 1, wherein a size of an overlapping region of two consecutive time-domain data blocks which are encoded in the frequency domain is larger than a size of an overlapping region of two consecutive time-domain data blocks of which one being encoded in the frequency domain and one being encoded in the time domain.

23. The apparatus of claim 1, wherein the overlapping of data blocks is being determined according to the AAC-specifications.

24. The apparatus of claim 1, further comprising a bypass for the processor and the overlap/add-combiner, the bypass being adapted for bypassing the processor and the overlap/add-combiner when non-overlapping consecutive time-domain data blocks incur in data segments which are encoded in the time domain.

25. A method for decoding data segments representing a time-domain data stream, a data segment being encoded in the time domain or in the frequency domain, a data segment being encoded in the frequency domain comprising successive blocks of data representing successive and overlapping blocks of time-domain data samples, wherein two consecutive time-domain data blocks of which one being encoded in the frequency domain and one being encoded in the time domain comprising a time domain overlapping region, comprising:

decoding a data segment being encoded in the time domain to acquire output data of the time-domain decoder;

processing the data segment being encoded in the frequency domain and the output data of the time-domain decoder to acquire overlapping time-domain data blocks for the time domain overlapping region; and

combining the overlapping time-domain data blocks in the time domain overlapping region to acquire a decoded data segment of the time-domain data stream for the time domain overlapping region.

26. A computer program comprising a program code for performing the method for decoding data segments representing a time-domain data stream, a data segment being encoded in the time domain or in the frequency domain, a data segment being encoded in the frequency domain comprising successive blocks of data representing successive and overlapping blocks of time-domain data samples, wherein two consecutive time-domain data blocks of which one being encoded in the frequency domain and one being encoded in the time domain comprising a time domain overlapping region, comprising:

decoding a data segment being encoded in the time domain to acquire output data of the time-domain decoder;

processing the data segment being encoded in the frequency domain and the output data of the time-domain decoder to acquire overlapping time-domain data blocks for the time domain overlapping region; and

combining the overlapping time-domain data blocks in the time domain overlapping region to acquire a decoded data segment of the time-domain data stream for the time domain overlapping region,

when the program code runs on a computer.

27. An apparatus for generating an encoded data stream based on a time-domain data stream, the time-domain data stream comprising samples of a signal, the apparatus comprising

a segment processor for providing data segments from the data stream, two consecutive data segments comprising a first or a second overlapping region, the second overlapping region being smaller than the first overlapping region;

a time-domain encoder for encoding a windowed data segment in the time domain;

a frequency-domain encoder for applying weights to samples of the time-domain data stream according to a first or second windowing function to acquire a windowed data segment, the first and second windowing functions being adapted to the first and second overlapping regions, the frequency-domain encoder being adapted for encoding a windowed data segment in the frequency domain;

a time-domain data analyzer for determining a transition indication associated with a data segment; and

a controller for controlling the apparatus such that for data segments comprising a first transition indication output data of the time-domain encoder is comprised by the encoded data stream and for data segments comprising a second transition indication, output data of the frequency-domain encoder is comprised by the encoded data stream.

28. The apparatus of claim 27, wherein the time-domain data analyzer is adapted for determining the transition indication from the time-domain data stream, the data segments or from data directly provided by the segment processor.

29. The apparatus of claim 27, wherein the time-domain data analyzer is adapted for determining a transition measure, the transition measure being based on the level of transience in the time-domain data stream or the data segment and wherein the transition indicator indicates whether a level of transience exceeds a predetermined threshold.

30. The apparatus of claim 27, wherein the segment processor is adapted for providing data segments with the first and the second overlapping regions,

the time-domain encoder is adapted for encoding the data segments,

the frequency-domain encoder is adapted for encoding the windowed data segments, and

the controller is adapted for controlling the time-domain encoder and the frequency-domain encoder such that for data segments comprising a first transition indication output data of the time-domain encoder is comprised by the encoded data stream and for windowed data segments comprising a second transition indication output data of the frequency-domain encoder is comprised by the encoded data stream.

31. The apparatus of claim 27, wherein the controller is adapted for controlling the segment processor for providing the data segments either to the time-domain encoder or the frequency-domain encoder.

32. The apparatus of claim 27, wherein the frequency-domain encoder is adapted for applying weights of windowing functions according to the AAC-specifications.

33. The apparatus of claim 27, wherein the frequency-domain encoder is adapted for converting a windowed data segment to the frequency domain to acquire a frequency-domain data segment.

34. The apparatus of claim 33, wherein the frequency-domain encoder is adapted for quantizing the frequency-domain data segment.

35. The apparatus of claim 34, wherein the frequency-domain encoder is adapted for evaluating the frequency-domain data segment according to a perceptual model.

36. The apparatus of claim 35, wherein the frequency-domain encoder is adapted for utilizing a cosine-modulated filterbank, an extended lapped transform, a low-delay filterbank or a polyphase filterbank to acquire the frequency-domain data segments.

37. The apparatus of claim 33, wherein the frequency-domain encoder is adapted for utilizing a modified discrete cosine transform to acquire the frequency-domain data segments.

38. The apparatus of claim 27, wherein the time-domain encoder is adapted for using a prediction filter for encoding the data segments.

39. A method for generating an encoded data stream based on a time-domain data stream, the time-domain data stream comprising samples of a signal, comprising

providing data segments from the data stream, two consecutive data segments comprising a first or a second overlapping region, the second overlapping region being smaller than the first overlapping region;

determining a transition indication associated with the data segments;

encoding a data segment in the time domain, and/or

applying weights to samples of the time-domain data stream according to a first or a second windowing function to acquire a windowed data segment, the first and second windowing functions being adapted to the first and second overlapping regions and encoding the windowed data segment in the frequency domain and;

controlling such that for data segments comprising a first transition indication output data being encoded in the time-domain is comprised by the encoded data stream and for data segments comprising a second transition indication output data being encoded in the frequency domain is comprised by the encoded data stream.

40. A computer program comprising a program code for performing the method for generating an encoded data stream based on a time-domain data stream, the time-domain data stream comprising samples of a signal, the method comprising

providing data segments from the data stream, two consecutive data segments comprising a first or a second overlapping region, the second overlapping region being smaller than the first overlapping region;

determining a transition indication associated with the data segments;

encoding a data segment in the time domain, and/or

applying weights to samples of the time-domain data stream according to a first or a second windowing function to acquire a windowed data segment, the first and second windowing functions being adapted to the first and second overlapping regions and encoding the windowed data segment in the frequency domain and;

controlling such that for data segments comprising a first transition indication output data being encoded in the time-domain is comprised by the encoded data stream and for data segments comprising a second transition indication output data being encoded in the frequency domain is comprised by the encoded data stream,

when the program code runs on a computer.