摘要:
A method for recording audio information on a record carrier, typically a bitstream signal on an optical disc, is disclosed. In the method the audio information is encoded to compressed audio data having a variable bitrate, in particular using lossless compression. The compressed audio data is recorded at a transfer speed which is controlled in dependence on the variable bitrate. A transfer speed profile (53, 54, 55) is determined for items of audio information, e.g. for each track on a CD, in which profile the average transfer speed is higher than an average transfer speed minimally required to transfer the compressed audio data of said item. Stuffing data is added to the compressed audio data according to the transfer speed profile, and transfer speed profile information is recorded on the record carrier for enabling playback at a transfer speed as indicated by the transfer speed profile information. Also a recording device, a record carrier and a playback device are disclosed.
摘要:
A method and apparatus is disclosed for determining a masked threshold curve as a function of frequency from an information signal. The method includes (a) a first step of determining for each frequency value a first masking component MC(1,k) at the frequency value f(k) resulting from a frequency component at the frequency value and having a magnitude equal to the magnitude value PV(k) of the magnitude spectrum at the frequency value, (b) a second step of determining for subsequent frequency values when going in one direction through the frequency range of interest a second masking component MC(2,k) at a frequency value, the second masking component for the frequency value being determined from the first masking component MC(1,k-1) and a second masking component MC(2,k-1) at only the frequency value directly preceding the frequency value f(k-1), (c) a third step of determining for subsequent frequency values when going in the reverse direction through the frequency range of interest a third masking component MC(3,k) at a frequency value, the third masking component for the frequency value being determined from masking information that has a relation to at least the first masking component MC(1,k+1) and the third masking component MC(3,k+1) at only the frequency value f(k+1) directly preceding the frequency value, and (d) a fourth step for determining a masking value MV(k) for a frequency value in the masked threshold curve from masking information that has a relation to the first, second and third masking components (if present) for the frequency value.
摘要:
An encoder apparatus is disclosed for encoding a wideband digital information signal. The apparatus comprises an input signal (1) for receiving the wideband digital information signal, a signal splitting unit (2) for splitting the wideband digital information signal into M narrow band sub signals (SB.sub.1 to SB.sub.M). The narrow bands all have a specific constant bandwidth. Further, a scale factor determining unit (6) for determining a scale factor for subsequent signal blocks in each of the sub signals, and a quantization unit (13) for quantizing the samples in a signal block into quantized samples are present. A bit allocation information deriving unit (34,41,48) is present for deriving bit allocation information, the bit allocation information being representative of the number of bits with which samples in a signal block of a sub signal will be represented after quantization in the quantization unit (13). A formatting unit (20) is present for combining the quantized samples in the signal blocks of the quantized sub signals and the scale factors into a digital output signal having a format suitable for transmission or storage. The apparatus further comprises a signal block length determining unit (30) for determining the lengths of the signal block in at least one of the sub signals and for generating block length information, the block length information being representative of the said lengths of the signal blocks of the said at least one sub signal, where the lengths of subsequent signal blocks in said at least one sub signal differ. The scale factor determining unit (6) now determines the scale factors for subsequent signal blocks of varying lengths in response to said block length information, the bit allocation information deriving unit (34,41,48) now derives bit allocation information for subsequent signal blocks of varying lengths in response to said block length information, and the quantization unit (13) now quantize the samples in signal blocks of varying lengths in response to said block length information. The formatting unit (20) further includes the block length information into the digital output signal for transmission or storage.
摘要:
An audio signal processing arrangement includes a first filter (20) for splitting off signal components from the left channel signal (L) at least within one frequency band. Signal components are split off from the right channel signal (R) by a second filter (23). The output signals of the filters (20 and 23) are compared with the right channel signal (R) and the left channel signal (L), respectively. The filter parameters of the filters (20 and 23) are adjusted to values at which there is maximum correlation between the compared signals according to a given criterion. The center channel signal is derived in dependence on the filter adjustment. This can be effected by combining the output signals of the filters (20 and 23). In this manner, a center channel signal is obtained formed by the correlating left and right channel signal components, so that the stereo image is hardly disturbed by the addition of the center channel signal, whereas the perceived position of the virtual sources in the stereo image becomes less dependent on the listener's position with respect to the left and right loudspeakers.
摘要:
A 7-channel encoder and corresponding decoder is disclosed for encoding a 7-channel signal into a transmission signal which is backwards compatible, so that prior art MPEG-1 2-channel decoders are capable of decoding the transmission signal into a compatible stereo signal, prior art MPEG-2 5-channel decoders are capable of decoding the transmission signal into a compatible 5-channel signal. Further, a 7-channel decoder is disclosed for decoding the transmission signal into a 7-channel signal. (FIG. 2).
摘要:
An encoding system and an encoding method for encoding a digital signal having at least a first and a second digital signal component. The encoding system includes a splitter unit for dividing the bandwidth of the digital signal components into M successive frequency bands, and generating in response to the digital signal components M sub signals (SB.sub.m1,SB.sub.mr) for each digital signal component, each sub signal of a signal component being associated with one of the frequency bands (m); a bit need determining unit for determining bit needs for time equivalent signal blocks of the sub signals, a signal combination unit for combining, in a number of at least one frequency bands, time equivalent signal blocks of corresponding sub signals of the at least first and second signal component so as to obtain a time equivalent signal block of a composite sub signal in each the at least one frequency bands; quantizing unit for quantizing time equivalent signal blocks of the sub signals in those frequency bands in which no composite sub signal is available and for quantizing the corresponding time equivalent signal blocks of the composite sub signal in the at least one frequency bands in which a composite sub signal is available. Further, a bit allocation unit is available for deriving allocation information (n.sub.mi,n.sub.jc) from bit needs obtained in the bit need determining unit and from a value B, where B corresponds to a number of bits in an available bitpool. The bit need determining unit is adapted to determine a common bit need b.sub.mc for a time equivalent signal block of a composite sub signal SB.sub.mc in a frequency band m from the bit needs b.sub.mi of the time equivalent signal blocks of the corresponding sub signals of the at least two signal components in that frequency band from which the time equivalent signal block of the composite sub signal has been derived, by taking the common bit need b.sub.mc equal to a weighted sum of the bit needs b.sub.mi. The encoding system can be a subband encoding system or a transform encoding system.
摘要:
The audio signal is divided into frequency sub-bands, the sub-band samples are quantized according to a predetermined quantizing criterion, and the quantized samples in one or more sub-bands are summed with samples of the auxiliary signal in such sub-bands, the auxiliary signal sample in a sub-band having a maximum amplitude less than half the quantization step used in such sub-band. The combined signal, covering the entire frequency band of the audio signal, can be transmitted or recorded on a record carrier. Upon audio reproduction at a receiver only the audio signal will be audible, the auxiliary signal being masked due to the psychoacoustic characteristics of the human auditory system which are unresponsive to low-level noise in the presence of high amplitude sound. The receiver includes a decoder which analyzes the combined signal into the original frequency sub-bands and re-quantizes the sub-band signals using the same quantizing criterion as at the coder. The auxiliary signal is reconstructed by subtracting the quantized signal sample in each sub-band from the non-quantized signal sample therein and combining the non-quantized sub-band signal sample. The auxiliary signal may be a copy inhibit code which serves to inhibit a recorder from recording the audio signal, thus protecting against unauthorized copying.