Audio signal encoder and method for generating a data stream having components of an audio signal in a first frequency band, control information and spectral band replication parameters
An audio signal synthesizer generates a synthesis audio signal having a first frequency band and a second synthesized frequency band derived from the first frequency band and comprises a patch generator, a spectral converter, a raw signal processor and a combiner. The patch generator performs at least two different patching algorithms, each patching algorithm generating a raw signal. The patch generator is adapted to select one of the at least two different patching algorithms in response to a control information. The spectral converter converts the raw signal into a raw signal spectral representation. The raw signal processor processes the raw signal spectral representation in response to spectral domain spectral band replication parameters to obtain an adjusted raw signal spectral representation.
1. An audio signal encoder for generating, from an audio signal, an audio data stream comprising components of the audio signal in a first frequency band, control information and spectral band replication parameters, comprising:
a frequency selective filter configured for generating the components of the audio signal in the first frequency band;
a generator configured for generating the spectral band replication parameter from the components of the audio signal in a second frequency band;
a control information generator configured for generating the control information, the control information identifying a patching algorithm from a first or a second different patching algorithm, wherein each patching algorithm generates a raw signal comprising signal components in the second replicated frequency band using the components of the audio signal in the first frequency band,
wherein the control information generator is configured for identifying the patching algorithm by comparing the audio signal with patched audio signals for the first and for the second patching algorithms, wherein differently patched audio signals are derived from different raw signals related to the first and the second patching algorithms by applying raw signal adjusting in response to spectral band replication parameters with a spectral band replication tool, and
an output interface configured for transmitting or storing the audio data stream representing the audio signal, the audio data stream comprising the components of the audio signal in the first frequency band, the control information and the spectral band replication parameters, wherein a bit rate for transmitting or storing the audio data stream is reduced compared to a bit rate for transmitting or storing the audio signal.
2. The audio signal encoder of claim 1 , further comprising an analyzer configured for analyzing the audio signal to provide the characteristic of the audio signal, wherein the analyzer is configured for identifying non-harmonic signal components for a time portion comprising a degree of voice or a harmonic signal component for a distinguished time portion.
3. A method for generating, from an audio signal, an audio data stream comprising components of the audio signal in a first frequency band, control information and spectral band replication parameters, comprising:
frequency selective filtering the audio signal to generate the components of the audio signal in the first frequency band;
generating the spectral band replication parameters from the components of the audio signal in a second frequency band;
generating the control information identifying a patching algorithm from a first or a second different patching algorithm, wherein each patching algorithm generates a raw signal comprising signal components in the second replicated frequency band using the components of the audio signal in the first frequency band,
wherein the generating the control information comprises:
deriving a first patched audio signal from a first raw signal related to the first patching algorithm comprising applying raw signal adjusting in response to spectral band replication parameters with a spectral band replication tool,
deriving a second patched audio signal from a second raw signal related to the second patching algorithm comprising applying raw signal adjusting in response to spectral band replication parameters with a spectral band replication tool,
comparing the audio signal with the first patched audio signal for the first patching algorithm,
comparing the audio signal with the second patched audio signal for the second patching algorithm; and
transmitting of storing the audio data stream representing the audio signal, the audio data stream comprising the components of the audio signal in the first frequency band, the control information and the spectral band replication parameters, wherein a bit rate for transmitting or storing the audio data stream is reduced compared to a bit rate for transmitting or storing the audio signal.
4. A non-transitory storage medium having stored thereon a computer program for performing, when running on a processor, a method for generating an audio data stream comprising components of an audio signal in a first frequency band, control information and spectral band replication parameters, the method comprising:
frequency selective filtering the audio signal to generate the components of the audio signal in the first frequency band;
generating the spectral band replication parameter from the components of the audio signal in a second frequency band;
generating the control information identifying a patching algorithm from a first or a second different patching algorithm, wherein each patching algorithm generates a raw signal comprising signal components in the second replicated frequency band using the components of the audio signal in the first frequency band,
wherein the patching algorithm is identified by comparing the audio signal with patched audio signals for the first and for the second patching algorithms, wherein differently patched audio signals are derived from different raw signals related to the first and the second patching algorithms by applying raw signal adjusting in response to spectral band replication parameters with a spectral band replication tool; and
transmitting or storing the audio data stream representing the audio signal, the audio data stream comprising components of the audio signal in a first frequency band, control information and spectral band replication parameters, wherein a bit rate for transmitting or storing the audio data stream is reduced compared to transmitting or storing the audio signal.
5. The audio signal encoder of claim 1 , wherein the output interface is configured for transmitting the audio data stream to a decoder decoding the audio data stream and synthesizing an audio output.
6. The audio signal encoder of claim 1 , wherein the control information generator is configured for identifying a patching algorithm resulting in the patched audio signal having a least deviation to the audio signal or identifying a number of patching algorithms or a ranking of patching algorithms resulting in patched audio signals yielding an agreement with the audio signal.
7. The audio signal encoder of claim 6 , wherein the control information generator is configured for performing an evaluation of the patched signal with respect to the deviation or the agreement with respect to a perceptual quality.
8. The audio signal encoder of claim 1 , wherein the control information generator is configured for generating the first patching signal or the second patching signal using at least one of the patching algorithms from a group of patching algorithms comprising:
(1) up sampling;
(2) mirroring of a spectrum;
(3) phase vocoding;
(4) non-linear distorting;
(5) mirroring of a spectrum in a QMF- (Quadrature Mirror Filtering-) domain by exchanging a QMF-band order; and
(6) performing a modulation.