# How best to digitize a noisy phone recording for filtering?

How do I digitize an analog telephone recording and filter it with a Chebyshev filter?

• What do you mean 'how to digitize'? I doubt you have an analogue input. It sounds like you want to convert from one format to another? If you want to know how to convert, then you should take this to StackExchange. – Spacey May 2 '12 at 20:42
• @Mohammad: good question. It is essential to draw the line between analog and digital. I am not sure my feeling is that I need digital format to do the operations but I am in the starting position about how to do it. My goal with this question is find out how to execute simple filters such as Chebyshev filter on some recording, not big question but essential to get right to make things clear. – user258 May 2 '12 at 21:12

## 1 Answer

Unless you have tight space constraints, I would stick to lossless formats like good old WAV. Phones do not pass much high-frequency content so you should be fine with a 8KHz Mono WAVE file. You will however want to keep the bit depth high, say to 24 bits, since you want to process the audio. Once you are finished with your processing you can compress with a lossy codec, such as OGG.

All codecs (coders/decoders) may be classified as lossy or lossless. Lossless codecs, as their name implies, allow for perfect reconstruction of the original signal. Lossy codecs, by contrast, merely approximate the source. By forgoing perfect fidelity, lossy codecs enable higher compression ratios, commensurate with the amount of degradation one is prepared to accept.

Perhaps related

• lossy codec apparently means the coding thing with lossy compression, more here. – user258 May 2 '12 at 23:16