Method of and system for coding and decoding sound signals

• US 20010013003A1
• Filed: 11/29/2000
• Published: 08/09/2001
• Est. Priority Date: 12/01/1999
• Status: Active Grant

• Current Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Original Assignee: US Philips Corporation (Koninklijke Philips N.V.)
• Inventors: Taori, Rakesh
• Granted Patent: US 7,069,210 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/02 using spectral analysis, e.g. transform vocoders or subband vocoders
• CPC Class Codes: H03M 13/00 Coding, decoding or code conversion, for error detection or error correction; Coding theory basic assumptions; Coding bounds; Error probability evaluation methods; Channel models; Simulation or testing of codes error detection or error correction for analogue/digital, digital/analogue or code conversion H03M1/00 – H03M11/00; specially adapted for digital computers G06F11/08; for information storage based on relative movement between record carrier and transducer G11B, e.g. G11B20/18; for static stores G11C

Abstract

Method of and system for coding a sound signal (10) as multiple independent streams of frames (14, 15) by creating frames (1,2,3,4,5,6) using sinusoidal coding and then placing frame i into stream i modulo the number of streams, method of and system for reconstructing a sound signal (23) by decoding frames from multiple streams (21, 22) in an interleaved fashion and reconstructing missing frames by using information from surrounding frames, system for recording and playing back sound signals implementing the above two methods, where under normal circumstances both streams (31, 32) of a coded signal are stored, and when capacity on the storage medium (35) is low, only one of the two streams of a coded signal is stored while one of the two streams of existing coded signals is overwritten and allowing a decoder (37) to reconstruct a sound signal by using either both or the one available stream for that sound signal.

Claims

1. A method of coding a sound signal as various streams of frames, in which the sound signal is subdivided into various segments and each segment is coded to a corresponding frame, characterized in that the sound signal is represented as a set of sine waves defined by their amplitude and frequency, in that the amplitude and the frequency of each sine wave in a segment are stored in a frame corresponding to this segment, independently of other segments, and in that the frames thus obtained are numbered and subdivided into n streams, where frame number i is subdivided into stream i modulo-n.

2. A coding method as claimed in

claim 1

, characterized in that also the phase of each sine wave in a segment is stored in the frame corresponding to this segment.

3. A coding method as claimed in

claim 1

or

2

, characterized in that n equals 2.

4. A method of decoding a sound signal which comprises various streams of numbered frames, in which each frame contains information about a segment of the sound signal, characterized in that an arbitrary stream is selected from the streams of frames, after which the sound signal is reconstructed by generating sine waves for each segment of the sound signal for which a corresponding frame is present in the selected stream, which sine waves are based on the information in the corresponding frame, and generating sine waves for each segment of the sound signal for which no corresponding frame is present in the selected stream, which sine waves are based on the information in the frames corresponding to a segment selected from a segment immediately preceding and a segment immediately following the respective segment.

5. A decoding method as claimed in

claim 4

, characterized in that sine waves are generated for a segment of the sound signal for which no corresponding frame occurs in the selected stream, but for which a corresponding frame does occur in another stream, which sine waves are based on the information in the corresponding frame from the other stream.

6. A system for coding a sound signal as various streams of frames, in which the sound signal is subdivided into various segments and each segment is coded to a corresponding frame, characterized in that the coding system comprises means for representing a sound signal as a set of sine waves defined by their amplitude and frequency, in that the amplitude and the frequency of each sine wave in a segment are stored in a frame that corresponds to this segment, independently of other segments, and in that the frames thus obtained are numbered and subdivided into n streams, where frame number i is assigned to stream i modulo-n.

7. A coding system as claimed in

claim 6

, characterized in that the coding system also includes means for storing the phase of each sine wave in a segment in the frame corresponding to this segment.

8. A coding system as claimed in

claim 6

or

7

, characterized in that n equals two.

9. A system for decoding a sound signal which comprises various steams of numbered frames, in which each frame contains information about a segment of the sound signal, characterized in that the decoding system is arranged for selecting an arbitrary stream from the streams of frames and then reconstructing the sound signal by generating sine waves for each segment of the sound signal for which a corresponding frame is present in the selected stream, which sine waves are based on the information in the corresponding frame, and for generating sine waves for each segment of the sound signal for which no corresponding frame is present in the selected stream, which sine waves are based on the information in the frames corresponding to a segment selected from a segment immediately preceding and a segment immediately following the respective segment.

10. A decoding system as claimed in

claim 9

, characterized in that the decoding system is also arranged for generating sine waves for a segment of the sound signal for which a corresponding frame does not occur in the selected stream, but for which a corresponding frame does occur in another stream, which sine waves are based on the information in the corresponding frame from the other stream.

11. A system arranged for recording and playing back sound signals, comprising a coder as claimed in

claim 8

, a storage system and a decoder as claimed in

claim 10

, in which:

the coder is arranged for applying two streams of frames to the storage system;

the storage system comprises a storage medium divided into at least a first and a second part, the storage system being arranged for being in one of the two states;

initially in a state A for storing the one stream offered by the coder in the first part of the storage medium and the other stream offered by the coder in the second part, and when the available free space on the storage medium falls short of a predefined limit, in a state B, in which the first part of the storage medium is no longer used for storing the offered streams, and the second part of the storage medium is intended to store one of the two offered streams while a stream stored in the second part in state A is overwritten; and

the decoder is arranged for receiving two streams of frames from the storage medium if the storage system is in state A and for receiving one stream from one of the parts of the storage medium if the storage system is in state B.