翻訳と辞書 Words near each other ・ Phase space formulation ・ Phase space method ・ Phase spider ・ Phase splitter ・ Phase Stretch Transform ・ Phase switch ・ Phase synchronization ・ Phase telescope ・ Phase Three ・ Phase transformation crystallography ・ Phase transition ・ Phase transitions and critical phenomena ・ Phase variation ・ Phase velocity ・ Phase VII ・ Phase vocoder ・ Phase-boundary catalysis ・ Phase-change Dual ・ Phase-change incubator ・ Phase-change material ・ Phase-change memory ・ Phase-coherent holography ・ Phase-comparison monopulse ・ Phase-contrast imaging ・ Phase-contrast X-ray imaging ・ Phase-fired controllers ・ Phase-locked loop ・ Phase-locked loop ranges ・ Phase-out of incandescent light bulbs ・ Phase-out of lightweight plastic bags Dictionary Lists mini英和辞書 mini和英辞書 Webster 1913 Latin-English FOLDOC Wikipedia English ウィキペディア

翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Phase vocoder ： ウィキペディア英語版 Phase vocoder A phase vocoder is a type of vocoder which can scale both the frequency and time domains of audio signals by using phase information. The computer algorithm allows frequency-domain modifications to a digital sound file (typically time expansion/compression and pitch shifting). At the heart of the phase vocoder is the short-time Fourier transform (STFT), typically coded using fast Fourier transforms. The STFT converts a time domain representation of sound into a time-frequency representation (the "analysis" phase), allowing modifications to the amplitudes or phases of specific frequency components of the sound, before resynthesis of the frequency domain representation into the time domain by the inverse STFT. The time evolution of the resynthesized sound can be changed by means of modifying the time position of the STFT frames prior to the resynthesis operation allowing for time-scale modification of the original sound file. == Phase coherence problem == The main problem that has to be solved for all case of manipulation of the STFT is the fact that individual signal components (sinusoids, impulses) will be spread over multiple frames and multiple STFT frequency locations (bins). This is because the STFT analysis is done using overlapping analysis windows. The windowing results in spectral leakage such that the information of individual sinusoidal components is spread over adjacent STFT bins. To avoid border effects of tapering of the analysis windows, STFT analysis windows overlap in time. This time overlap results in the fact that adjacent STFT analysis are strongly correlated (a sinusoid present in analysis frame at time "t" will be present in the subsequent frames as well). The problem of signal transformation with the phase vocoder is related to the problem that all modifications that are done in the STFT representation need to preserve the appropriate correlation between adjacent frequency bins (vertical coherence) and time frames (horizontal coherence). Except in the case of extremely simple synthetic sounds, these appropriate correlations can be preserved only approximately, and since the invention of the phase vocoder research has been mainly concerned with finding algorithms that would preserve the vertical and horizontal coherence of the STFT representation after the modification. For time scaling operations amplitude coherence is only a minor problem because shifting analysis frames in time has only a minor impact on the amplitude. The phase coherence problem was investigated for quite a while before appropriate solutions emerged. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Phase vocoder」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.