Audio coding

• US 20070185707A1
• Filed: 03/08/2005
• Published: 08/09/2007
• Est. Priority Date: 03/17/2004
• Status: Active Grant

• Current Assignee: Koninklijke Philips N.V.
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Den Brinker, Albertus, Gerrits, Andreas
• Granted Patent: US 7,587,313 B2
• Time in Patent Office: Days
• US Class Current: 704/201
• CPC Class Codes: G10L 19/022 Blocking, i.e. grouping of samples in time; Choice of analysis windows; Overlap factoring
• CPC Class Codes: G10L 19/093 using sinusoidal excitation models
• CPC Class Codes: G10L 19/20 using sound class specific coding, hybrid encoders or object based coding

Abstract

The method creates an audio stream comprising tracks of sinusoidal components linked across a plurality of sequential time segments. Segments in each track are weighted with a normal window (WI, W2, W3), and consecutive segments have a normal period of overlap (0) of their trailing edges and leading edges. Segments in which a transient 5 component is determined are weighted with a first modified window (WIm) having a modified trailing edge, and the following segment in the track is weighted with a second modified window (W2m) having a modified leading edge, so that the modified trailing edge and the modified leading edge have a modified period of overlap (0m) that comprises the transient component and that is shorter than the normal period of overlap (0), and wherein the audio stream includes sinusoidal codes representing the frequency and the transient. According to the invention, the modified period of overlap (0m) depends on the frequency value (f).

Claims

1. A method of synthesising a signal comprising sinusoids from encoded data, the encoded data comprising, for each of a plurality of consecutive time segments, one or more frequency values (f) representing sinusoids, and data identifying the time of occurrence of possible transients, the method comprising generating sinusoids with each of the one or more frequency values (f), and linking sinusoids across a plurality of consecutive segments, where segments with no transients are weighted with a normal window (W1, W2, W3) having a normal leading edge and a normal trailing edge, and where consecutive segments have a normal period of overlap (O) of their trailing edges and leading edges, respectively, and where segments in which the time of occurrence of a transient is identified, are weighted with a first modified window (W1m) having a modified trailing edge, and the following segment is weighted with a second modified window (W2m) having a modified leading edge, so that the modified trailing edge and the modified leading edge have a modified period of overlap (Om), which comprises the time of the occurrence of the transient, and which is shorter than the normal period of overlap (O), wherein the modified period of overlap (Om) depends on the frequency value (f).

2. A method according to claim 1, wherein the modified period of overlap (Om) decreases with increasing frequency value (f).

3. A method according to claim 1, wherein the modified period of overlap (Om) depends on the frequency value (f) substantially as f^1/c.

4. A method according to claim 1, wherein two or more fixed values of the modified period of overlap (Om) are used for corresponding frequency intervals.

5. An audio decoder for synthesising a signal comprising sinusoids from encoded data, the encoded data comprising, for each of a plurality of consecutive time segments, one or more frequency values (f) representing sinusoids, and data identifying the time of occurrence of possible transients, the audio decoder being adapted to use the method of claim 6.

6. An audio encoder for encoding a signal adapted to use the method of any claim 1.