27 research outputs found
Noise Weighting in the Design of {\Delta}{\Sigma} Modulators (with a Psychoacoustic Coder as an Example)
A design flow for {\Delta}{\Sigma} modulators is illustrated, allowing
quantization noise to be shaped according to an arbitrary weighting profile.
Being based on FIR NTFs, possibly with high order, the flow is best suited for
digital architectures. The work builds on a recent proposal where the modulator
is matched to the reconstruction filter, showing that this type of optimization
can benefit a wide range of applications where noise (including in-band noise)
is known to have a different impact at different frequencies. The design of a
multiband modulator, a modulator avoiding DC noise, and an audio modulator
capable of distributing quantization artifacts according to a psychoacoustic
model are discussed as examples. A software toolbox is provided as a general
design aid and to replicate the proposed results.Comment: 5 pages, 18 figures, journal. Code accompanying the paper is
available at http://pydsm.googlecode.co
Coding of Stereo Signals by a Single Digital {\Delta}{\Sigma} Modulator
The possibility of using a single digital {\Delta}{\Sigma} modulator to
simultaneously encode the two channels of a stereo signal is illustrated. From
the modulated stream, the two channels can be recovered with minimal processing
and no cross-talk. Notably, demultiplexing does not affect the sample-depth so
that, after it, one still has a data stream suitable for directly driving a
power bridge and convertible into analog by mere low-pass filtering.
Furthermore, the approach is very flexible and if one channel is unused, it
lets the other get improved dynamic range and SNR. The approach can take
advantage of recent techniques for the design of {\Delta}{\Sigma} modulators,
including methods for psychoacoustically optimal distribution of quantization
noise. Code is available to replicate the proposed examples and as a general
computer aided design tool.Comment: 4 pages, 5 figures. Pre-print from conference proceeding
量子化誤差削減のためのΔΣ変調器のノイズ整形フィルタの設計
広島大学(Hiroshima University)博士(工学)Doctor of Engineeringdoctora
Perceptual models in speech quality assessment and coding
The ever-increasing demand for good communications/toll
quality speech has created a renewed interest into the
perceptual impact of rate compression. Two general areas are
investigated in this work, namely speech quality assessment
and speech coding.
In the field of speech quality assessment, a model is
developed which simulates the processing stages of the
peripheral auditory system. At the output of the model a
"running" auditory spectrum is obtained. This represents
the auditory (spectral) equivalent of any acoustic sound such
as speech. Auditory spectra from coded speech segments serve
as inputs to a second model. This model simulates the
information centre in the brain which performs the speech
quality assessment. [Continues.
Improved compactly computable objective measures for predicting the acceptiability of speech communications systems
Issued as Monthly status reports [1-7], and Final report, Project no. E-21-61
Proceedings of the Mobile Satellite Conference
A satellite-based mobile communications system provides voice and data communications to mobile users over a vast geographic area. The technical and service characteristics of mobile satellite systems (MSSs) are presented and form an in-depth view of the current MSS status at the system and subsystem levels. Major emphasis is placed on developments, current and future, in the following critical MSS technology areas: vehicle antennas, networking, modulation and coding, speech compression, channel characterization, space segment technology and MSS experiments. Also, the mobile satellite communications needs of government agencies are addressed, as is the MSS potential to fulfill them