Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
2000-03-08
2001-09-11
Dorvil, Richemond (Department: 2641)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S230000, C370S389000, C370S470000, C370S480000, C375S242000
Reexamination Certificate
active
06289308
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an article of manufacture which is a transmission signal produced by encoding a wideband digital signal of a specific sampling frequency F
s
, for example a digital audio signal, in an encoder, the transmission signal comprising consecutive frames, each frame comprising a plurality of information packets (IP), each information packet being N bits long, N being larger than 1, and a frame comprising at least a first frame portion including synchronization information. The invention also relates to an article of manufacture which is a record carrier in which such a signal is recorded.
2. Description of the Prior Art
A transmission signal as defined above can be used in a transmission system of the type known from the article, “The Critical Band Coder—Digital Encoding of Speech Signals Based on the Perceptual Requirement of the Auditory System” by M. E. Krasner, published in Proc. IEEE ICASSP 80, Vol. 1, pp 327-331, Apr. 9-11, 1980. This article relates to a transmission system in which the transmitter employs a subband coding system and the receiver employs a corresponding subband decoding system.
In this known coding system the speech signal band is divided into a plurality of frequency subbands whose bandwidths approximate the bandwidths of the critical bands of the human ear in the respective frequency ranges (see
FIG. 2
of this article). This division is selected because, based on psycho-acoustic experiments, one can expect that quantization noise in such a subband will be masked to an optimum extent by the signals in that subband, if during quantization allowance is made for the noise-masking curve of the human ear. Threshold values for noise masking by single tones in the center of a critical band are shown in
FIG. 3
of this article.
When applying frequency subband coding to a high-quality digital music signal, such as one according to the Compact Disc Standard which uses 16 bits per signal sample at a sample frequency of 1/T=44.1 kHz, with a suitably selected bandwidth and a suitable selected quantization for the respective subbbands, the quantized output signals of the coder can be represented by an average number of approximately 2.5 bits per signal sample. The quality of the replica of the music signal does not differ perceptibly from that of the original music signal in substantially all passages of substantially all kinds of music signals.
The subbands need not necessarily correspond to the bandwidths of the critical bands of the human ear. For example, the subbands may have equal bandwidths, provided that allowance is made for this in determining the masking threshold.
Other types of transmission signals are known with which the invention may be used, such as those in which blocks of samples are transform coded. Such systems are referred to in the article “Low bit-rate coding of high-quality audio signals. An introduction to the MASCAM system” by G. Thiele, G. Stoll and M. Link, published in EBU Technical Review, no. 230, pp. 71-94, August 1988. In such a system the transform coefficients correspond to sub-signals.
The sub-signal transmission systems described above have the disadvantage that, in some cases, perceptible differences occur between the replica and the original unencoded signal which was to be transmitted. These differences are perceived as a form of distortion in the replica generated by the receiver. Often they are the result of transmission signal or record carrier bandwidth requirements which limit the number of bits available for quantization of certain of the sub-signals.
SUMMARY OF THE INVENTION
An object of the invention is to provide a transmission signal to enable more efficient transmission of a wideband digital signal.
Another object of the invention is to provide a record carrier in which a more efficiently transmitted wideband digital signal is recorded.
In a transmission signal according to the invention, the number B of information packets, each composed of N bits, in one frame has a relation to a value P, such that,
(i) if P in the formula
P=(BR×n
s
)/(N×F
s
)
is an integer, where BR is the bit rate of the transmission signal, n
s
is the number of samples of the wideband digital signal whose corresponding information in the transmission signal is included in one frame of the transmission signal, and F
s
is the sampling frequency, the number B of information packets in one frame is P, or
(ii) if P is not an integer, the number B of information packets in a number of frames is P′, where P′ is the next lower integer following P, and the number of information packets in the other frames is equal to P′+1 so as to exactly comply with the requirement that the average frame rate of the transmission signal is substantially equal to F
s
s
.
The purpose of dividing the frames into B information packets is that, for a wide-band digital signal of a sampling frequency F
s
, the average frame rate of the transmission signal received is now such that the average duration of a frame in the digital signal corresponds to the duration occupied by n
s
samples of the wide-band signal.
Preferably, the first frame portion further contains information related to the number of information packets in a frame. In a frame comprising B information packets this information may be equal to the value B. This means that this information corresponds to P′+1 for frames comprising P′ information packets and to P′+1 for frames comprising P′+1 information packets. Another possibility is that this information corresponds to P′ for all frames, regardless of whether a frame comprises P′ or P′+1 information packets. The additionally inserted (P′+1)th information packet may comprise for example merely “zeros”. In that case this information packet does not contain any useful information. Of course, the additional information packet may also be filled with useful information.
The first frame portion may further comprise system information. This may include the sample frequency F
s
of the wide-band digital signal applied to the transmitter, copy-protection codes, the type of wide-band digital signal applied to the transmitter, such as a stereo-audio signal or a mono-audio signal, or a digital signal comprising two substantially independent audio signals. However, other system information is also possible, such as the bit rate, as will become apparent hereinafter. Including the system information makes it possible for the receiver and thus the decoder in the receiver to be flexible and enables the transmission signal received to be correctly reconverted into the wide-band digital signal.
The frames may comprise second and third frame portions. Those frame portions contain other signal information, such as allocation information, quantized samples and scale factor information. Upon encoding, the wideband digital signal can be split up so as to generate a number M of subsignals, M being larger than 1. Those subsignals are quantized so as to obtain quantized subsignals. For this purpose an arbitrary encoding, such as a transform coding or a subband coding, may be used. At the receiving end it is then necessary to apply an inverse encoding (usually described as decoding) on the transmission signal received in order to recover the wideband digital signal.
Preferably, the allocation information is inserted in a frame before the samples. This allocation information is needed to enable the continuous serial bit stream of the samples in the third frame portion to be subdivided into the various individual quantized samples of the correct number of bits at the receiving end. An adaptive bit allocation method is among the matters described in the publication “Low bit-rate coding . . . ” by G. Theile et al referred to above. Inserting the allocation information in a frame before the samples in a frame has the advantage that in the decoder a simpler decoding becomes possible, which c
Dorvil Richemond
Goodman Edward W.
McFadden Susan
U.S. Philips Corporation
LandOfFree
Encoded wideband digital transmission signal and record... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Encoded wideband digital transmission signal and record..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Encoded wideband digital transmission signal and record... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2498387