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1200/2400bps改进型多激励声码器的实时实现 总被引:2,自引:0,他引:2
本文介绍了基于多带激励(MBE)语音模型的改进型全双工1200/2400bps声码器,该声码器已应用于多种通信系统中,其语音清晰度(DRT标准)1200bps时为91.75,2400bps时为92.67。本文重点介绍其硬件结构及算法实现。 相似文献
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语音增强IMBE声码器研究 总被引:1,自引:0,他引:1
多带激励声码器(MBE)由MIT的Grifin在1987年提出,其改进算法(IMBE)已被IN-MARSAT采纳作为卫星话音通信的标准。MBE声码器在中低速率上可获得较好的合成语音质量,但在噪声环境中使用时,随着输入信噪比的降低,其性能将显著恶化。本文试图将语音增强技术与MBE模型相结合以提高声码器抗噪声的性能。我们研究了两种方案:一是采用语音增强预处理器和IMBE声码器级联,二是将语音增强技术和IMBE声码器有机结合构成语音增强IMBE声码器。客观测试和主观试听表明,这两种系统在噪声环境中工作时,性能都有很大的提高。 相似文献
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在电力线上进行数据通信的调制解调器芯片ST7536 总被引:1,自引:0,他引:1
ST7536是一种半双工同步调频调制解调器,可在电力线上以600bps或1200bps的速率进行数据传输,从而省去专用通信线,降低成本,缩短安装时间。本文介绍了该芯片的特性、功能、原理、与应用。 相似文献
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本文介绍了一种将应用于第三代移动通信的新型语音声码器-变速率多模式宽带(VMR-WB)声码器。VMRWB 专为CDMA2000标准设计,有效语音带宽扩展为:50 Hz=7000 Hz,有四种不同速率的运行模式,每一种模式对应一定质量的平均数据速率。在相同的速率下,VMR-WB语音声码器的主观质量和性能较现有的窄带和宽带编码标准都有明显的提高。本文主要介绍其编码原理以及一些特性。 相似文献
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本文引入子波包算法,在语音信号的子波包子空间里判决语音的基音,从而可以有效避开有色噪声(如低频噪声)等的干扰,正确提取语音的基音。这种方法不仅能提高低速率声码器在无噪环境下的语音质量,而且能在很强的有色噪声环境下保持原有的声码器音质,从而有效地克服低速声码器抗噪能力差的缺点。 相似文献
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该文介绍了基于多带激励(MBE) 语音模型的改进型800/920/1200bps 语音编码器。该编码器采用二级离散余弦变换编码方案对逐帧变化的谱幅度参数进行自适应动态量化编码,大大减小了编码比特率,使得800~1200bps速率的MBE语音编码器的实现成为可能。该文重点介绍二级离散余弦变换编码方案及DSP硬件实现。 相似文献
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This paper reviews the main algorithms for speech coding at low and very low bit rates, from 50 bps to 4 000 bps. Then the hsx technique for coding at 1200 bps and a new segmental method with automatically derived units for very low bit rate coding are presented in details. 相似文献
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低速率声码器中残差谱的变维矢量量化 总被引:3,自引:0,他引:3
基于一个基音周期内语音线性预测残差波形,提出了一种简单而有效的LPR谱变维矢量量化(VDVQ)方法,即利用具有固定维数的通用码本对LPR谱幅度形状进行了矢量量化,通用码本和结构化的VQ相组合减少了存储和计算复杂度,产生了高的量化效率,增强了编码语音的感怀质量计算机仿真结果表明,利用该VDVQ技术设计的2.4kb/s语音编码器产生了高质量合成语音。 相似文献
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Yohtaro Yatsuzuka Tomohiro Yamazaki Shigeru Hzuka 《International Journal of Satellite Communications and Networking》1986,4(4):193-202
This paper describes applications of adaptive predictive coding (APC) with maximum likelihood quantization (MLQ) which can cover a wide range of coding rates from 4.8 to 16 kb/s for low C/N satellite communication systems, such as maritime, aeronautical mobile and thin-route satellite communication systems, and also for speech and data integration, including digital circuit multiplication equipment (DCME) in business communication systems, such as INTELSAT business services (IBS). A 16 kb/s APC–MLQ hardware codec has been implemented by NEC–7720 DSP chips and the performance has been confirmed in subjective quality of speech through conversational tests. The objective performance has also been evaluated for non-voice signals, such as single and multi-frequency tones, and 1200 and 2400 b/s voiceband data signals. The APC-MLQ codec can transmit the voice-band data at 1200 b/s over two asynchronous tandem links and at 2400 b/s over one link. It was noted that the APC-MLQ codec is superior in speech performance at 16 kb/s to a narrow-band companded FM and meets requirements for low C/N satellite communication systems. For voice and data integration into 16 kb/s for 64 kb/s links, we propose a multi-media multiplexing for low C/N digital satellite communication systems and also a small-scale circuit multiplication system for business use. In these systems, a variable rate coding of APC-MLQ from 4.8 to 16 kb/s can be effectively introduced for voice and data integration. 相似文献
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MSM6882是日本OKI公司生产的、采用最小频移键控方法的数据调制解调器。该器件内含接收、发送和时钟产生电路,且数据传输波特率可在1200bps和2400bps中选择。文中介绍了MSM6882的主要性能和工作原理,给出了MSM6882在无线通信中的应用电路设计。 相似文献
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Bao Changchun 《通信学报》1998,19(5):0
ANovelLowbitrateSpechCodingBasedonDecompositionofthePitchcycleWaveformoftheLinearPredictiveResidualBaoChangchun(Departm... 相似文献
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Investigation of multicarrier modulation has demonstrated the feasibility of using this modulation format to deliver relatively high channel bit rates (24 kbps) to a low cost, pager-like personal communications service (PCS) terminal that enjoys long battery life (e.g., one month on a few pen-light cells). This is to be compared to the 1200 bps carried by typical current paging systems or the 6250 bps attained by the new ERMES paging system. While more complex modulation formats, such as PSK and QAM, might achieve higher bit rates in less (power, size, cost) constrained environments, amplitude keying of the component subcarriers allows simple noncoherent energy detection that is found to be robust in this short message delivery application 相似文献