Hybrid Wyner-Ziv coders which employ a combination of Wyner-Ziv coding and differential pulse code modulation (DPCM) encoding have recently gained popularity for applications such as video coding. In this paper we ana...
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ISBN:
(纸本)9781424414833
Hybrid Wyner-Ziv coders which employ a combination of Wyner-Ziv coding and differential pulse code modulation (DPCM) encoding have recently gained popularity for applications such as video coding. In this paper we analyze the low-rate operational rate distortion performance of Wyner-Ziv coding using uniform scalar quantization, in the context of such hybrid coders. Motivated by video we consider the compression of a first-order Laplace-Markov source, and derive approximate analytical rate and distortion expressions which are accurate at lowrates. We utilize the derived analytical expressions to address the problem of determining the optimal quantization interval ratio of the Wyner-Ziv and DPCM scalar quantizers, for a range of rates.
The intelligibility of speech transmitted through low-rate coders is severely degraded when high levels of acoustic noise are present in the acoustic environment. Recent advances in nonacoustic sensors, including micr...
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The intelligibility of speech transmitted through low-rate coders is severely degraded when high levels of acoustic noise are present in the acoustic environment. Recent advances in nonacoustic sensors, including microwave radar, skin vibration, and bone conduction sensors, provide the exciting possibility of both glottal excitation and, more generally, vocal tract measurements that are relatively immune to acoustic disturbances and can supplement the acoustic speech waveform. We are currently investigating methods of combining the output of these sensors for use in low-rate encoding according to their capability in representing specific speech characteristics in different frequency bands. Nonacoustic sensors have the ability to reveal certain speech attributes lost in the noisy acoustic signal;for example, low-energy consonant voice bars, nasality, and glottalized excitation. By fusing nonacoustic low-frequency and pitch content with acoustic-microphone content, we have achieved significant intelligibility performance gains using the DRT across a variety of environments over the government standard 2400-bps MELPe coder. By fusing quantized high-band 4-to-8-kHz speech, requiring only an additional 116 bps, we obtain further DRT performance gains by exploiting the ear's insensitivity to fine spectral detail in this frequency region. Index Terms-Intelligibility, low-rate coding, nonacoustic sensors.
The low-rate (< 1 bits per sample) operational rate-distortion performance of uniform scalar quantizers for the memoryless Gaussian source is studied. Approximate analytical expressions for the operational rate-dis...
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ISBN:
(纸本)9781424404810
The low-rate (< 1 bits per sample) operational rate-distortion performance of uniform scalar quantizers for the memoryless Gaussian source is studied. Approximate analytical expressions for the operational rate-distortion function are derived, and the accuracy of the derived function is verified through simulation. It is shown that in the zero-rate limit the derived operational rate-distortion function is first-order optimal with respect to the Shannon lower bound. The derived function is used to study the performance of uniform scalar quantizers for the Gaussian Wyner-Ziv problem. Lastly, the derived low-raterate-distortion function is used to provide improved low-rate bit allocation for jointly Gaussian vectors.
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