Upsampling PCMU

Is there an algorithm for upsampling PCMU without开发者_StackOverflow社区 having to convert it to PCM first? Are the standard interpolation algorithms applicable to PCMU encoded samples?

Decoding and re-encoding mu law is very simple, and probably easier than trying to work out the potential aliasing implications of interpolating mu-law. You'll probably want to apply a low pass filter after upsampling, for which you would need to decode and re-encode anyway.