zeckill

刚才问过HKBN 2b，他们的Technical Support Personnel也不能提供这方面的信息。那么我们采用ulaw可能会比较 ...
角色 發表於 2010-9-10 12:54

HKBN 2b 係用 alaw 的，其實兩者 algo 查唔多，而且兩者之間 transcoding is very cheap in terms of CPU cycle. Asterisk 本身就有 ulaw/alaw transcoder module (codec_a_mu.so). 你睇下 Asterisk CLI: "show translation" 就會知 how cheap it is to transcode between the two.

According to Wikipedia, the differences are:
"The µ-law algorithm provides a slightly larger dynamic range than the A-law at the cost of worse proportional distortion for small signals. By convention, A-law is used for an international connection if at least one country uses it."

可能因為咁所以 2b 會選用 alaw.