大家新年好！ 可否討論一下48khz24bit的聲音檔案如果轉換到441khz16bit的話，它們之間是用一種什麽樣的運算方式來計算？那反之，若將441-16的文件轉到48，24的話，最後的結果還會保持原始文件的原貌嗎? 在這個環節，如果使用Dither是否還具有它的意義？ 另外請問uv22的技術同樣適用於96k 或192k嗎？ 望賜教！謝謝！
回ADDA There are two basic digital audio parameters,..... "quantization or bits" and "sample rate"..., these two have to be accounted for when converting a digital audio sample to another. Changing quantization accuracy is easy,,,, if the destination system has more bits per sample than the source system,...... just pad the source samples with zeros or ones.... More complex schemes are also available,..... BUT they really CAN NOT give the end user any benefit in "SOUND QUALITY" !!!...... If the destination system has less bits per sample than the source system, the change can be easily be made by just dropping the "less significant bits"(LSB) away..... This will naturally cause "loss of S/N ratio"....... The effect can be somewhat lessened by using "dithering" or other ingenious (and often patented) techniques..,,, Nevertheless, changing quantization is basically trivial... However,.... converting between different sample rates is a totally different thing.,,,, Unlike with quantization levels, where you can easily find bit-to-bit correspondence, there is no such consistency when converting between different "sample rates".,,,,,,,, The "easiest way"... to convert between sample rates is to read input samples and every time an output sample is requested, just give the last read value. However, this is totally insufficient. When converting this way the original frequencies found in the data signal are mirrored at worst several times and these mirror images cause the original signal to sound very bad indeed.,,,,, Using so-called "FIR" filters ,,,, it is easy to do sample rate conversions between some given sample ratios. For instance, converting 8 kHz to 48 kHz is quite easy, because 48 is divisable by 8. However, a more general approach is needed if one wishes to be able to convert any sample rate to any other arbitrary sample rate.,,,,,,, Digital upconversion is used practically everywhere. For instance, if a CD player claims to have "8X oversampling", what does it mean? It means that the signal is upconverted from 44.1 kHz to 352 kHz to get all harmful frequencies caused by digital reproduction to an inaudible area. This will cause mirrored frequencies to occupy the range of 330..352 kHz instead of 22..44 kHz. The point is that making an analog filter that filters everything over, say, 100 kHz, is easy to do, whereas it is next to impossible to build an analog filter that would pass on everything between 0..20 kHz and reject everything over 24 kHz....... The hard part in converting between digital signals is changing the sample rate. If downconverting, some information is always "lost" because the "higher voices" cannot be represented with the new, lower sample rate. If upconverting, care must be taken not to introduce new information to the conversion that wasn't there in the first place.....Easy to say,,,hard to be done perfectly,,,,,,,, Usually sample rate conversion systems are rigid, and can only do an up- or downconversion of a certain integer ratio, like in the CD 8X oversampling example. This is because up- or downconverting with a small integer ratio is an easy thing to do. What is much harder, is to create a converter that can convert any input sample rate to any output sample rate. It is even harder if both of there signals have to be created in real-time, and especially if the input and output sample rates may vary little because of jitter or other real life imperfections. </font><blockquote>引言:</font><hr /> 另外請問uv22的技術同樣適用於96k 或192k嗎？</font>[/QUOTE]UV22 is working on "Bit Depth" or say "word-length" only,,,especially on downversion bits converting only..,UV-22 has nothing to do with sampling rate,,,,,so considering it could be applied,,,,,, Apogee do sell some 96 KHz AD/DA within UV-22,,(PSX-100 and AD8000...)....but I never reckon the 'UV-22' is handy in anyway,,so,,I don't give a penny !!....
You are welcome !!,,, some extra for the new year's gift,,, If you just want to transferring audio files from formats to formats in totally digital domain,,,some "Batch" software is acturally quite comprehensive enought,,, here is one for PC.... http://www.fmjsoft.com/aamain.shtml