Encoder, decoder and methods for encoding and decoding data segments representing a time-domain data stream

• US 9,355,647 B2
• Filed: 03/03/2015
• Issued: 05/31/2016
• 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, Neuendorf, Max, Yokotani, Yoshikazu, Rettelbach, Nikolaus, Herre, Juergen, Geyersberger, Stefan
• Primary Examiner(s): YEN, ERIC L
• Application Number:
  US14/637,256
• Publication Number:
  US 20150179183A1
• Time in Patent Office: 455 Days
• US Class Current: 1/1
• 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 audio data stream or a time domain video data stream, wherein one or more data segments are encoded in the time domain, and wherein one or more data segments are encoded in the frequency domain, wherein the data segments which are encoded in the frequency domain represent time-domain data samples of overlapping data blocks, the apparatus comprising:

a time-domain decoder adapted to decode a data segment, which is encoded in the time domain, to acquire output data of the time-domain decoder;

a processor adapted to process the data segments, which are encoded in the frequency domain, and the output data of the time-domain decoder to acquire time domain data blocks, such that time domain data blocks obtained based on consecutive data segments which consecutive data segments are encoded in the frequency domain, overlap, and such that consecutive time domain data blocks of which one was encoded in the frequency domain and of which one was encoded in the time domain, overlap; and

an overlap/add-combiner adapted to combine the overlapping time-domain data blocks to acquire the decoded data segments of the time-domain data stream;

wherein the processor comprises a calculator for adapted to calculate overlapping time-domain data blocks based on the output data of the time-domain decoder;

wherein the calculator is adapted to reproduce, based on the output data of the time-domain decoder, an overlapping property of a frequency-domain to time-domain converter; and

wherein the calculator is adapted to reproduce, based on the output data of the time-domain decoder, a time-domain aliasing characteristic of the frequency-domain to time-domain converter,

wherein the apparatus is implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

2. The apparatus of claim 1, wherein the processor comprises a frequency-domain decoder adapted to decode data segments, which data segments are encoded in the frequency domain, to acquire frequency-domain data segments.

3. The apparatus of claim 1, wherein the processor is adapted to process a data segment, which is encoded in the time domain and in the frequency domain in parallel, such that two codecs operate in parallel.

4. The apparatus of claim 2, wherein the processor comprises a time-domain to frequency-domain converter adapted to convert 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 adapted to combine the frequency-domain data segments with 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 adapted to convert 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 to use a prediction filter to decode a data segment encoded in the time domain.

12. The apparatus of claim 6, wherein the frequency-domain to time-domain converter is adapted to convert the frequency-domain data segments, which are acquired by the frequency-domain decoder, to provide overlapping time-domain data blocks.

13. The apparatus of claim 12, wherein the overlap/add-combiner is adapted to combine the overlapping time-domain data blocks provided by the frequency-domain to time-domain converter and by the processor, to acquire decoded data segments of the time-domain data stream.

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

15. The apparatus of claim 1, wherein the calculator is adapted to

segment the output of the time-domain decoder into calculator segments, the calculator segments comprising 2N sequential samples,

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

subtract, in reversed order, the first N/2 samples from the second N/2 samples, add the fourth N/2 samples, in reversed order, to third N/2 samples, invert the second N/2 samples and third N/2 samples

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

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

apply weights, according to a synthesis windowing function, to the 2N samples.

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

17. The apparatus of claim 16, wherein the overlap/add-combiner is adapted to apply weights according to a synthesis windowing function which synthesis windowing function is adapted to a size of an overlapping region of consecutive overlapping time-domain data blocks.

18. The apparatus of claim 17, wherein the calculator is adapted to apply, according to an analysis windowing function which is adapted to a size of an overlapping region of consecutive overlapping time-domain data blocks, weights to 2N samples and wherein the calculator is adapted to apply, according to a synthesis windowing function which is adapted to the size of the overlapping region, weights to the 2N.

19. 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 is encoded in the frequency domain and one is encoded in the time domain.

20. The apparatus of claim 1, wherein an overlapping of respective data blocks is determined according to the AAC-specifications.

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

22. A method for decoding data segments representing a time-domain audio data stream or a time-domain video data stream, wherein one or more data segments are encoded in the time domain, wherein one or more data segments are encoded in the frequency domain, comprising wherein the data segments which are encoded in the frequency domain represent time-domain data samples of overlapping data blocks, comprising:

decoding a data segment which is encoded in the time domain to acquire output data of the time-domain decoding;

processing the data segments which are encoded in the frequency domain and the output data of the time-domain decoding to acquire time-domain data blocks for, such that time-domain data blocks obtained based on consecutive data segments which consecutive data segments are encoded in the frequency domain, overlap, and such that consecutive time-domain data blocks of which one was encoded in the frequency domain and of which one was encoded in the time domain, overlap; and

combining the overlapping time-domain data blocks to acquire the decoded data segments of the time-domain data stream,

wherein the overlapping time-domain data blocks are calculated based on the output data of the time-domain decoding;

wherein an overlapping property of a frequency-domain to time-domain conversion is reproduced based on the output data of the time-domain decoding; and

wherein a time-domain aliasing characteristic of the frequency-domain to time-domain conversion is reproduced based on the output data of the time-domain decoding,

wherein the method is performed using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

23. A non-transitory computer readable medium comprising a computer program

adapted to perform the method according to claim 22 when the program code runs on a computer.