Amr generally refers to AMR-Nb, which is 8 KHz sampling and has 8 bit rate encoding/decoding methods.Algorithm. In addition, there are nine bit rate encoding algorithms for AMR-WB, namely 16 KHz sampling. Because the AMR-WB sampling rate is high, the complexity is about twice that of AMR. Both AMR and Amr-WB belong to the speech codec, which does not work well in Audio Encoding. To improve the audio encoding performance, Amr-WB + appears. Amr-WB + supports higher sampling rates. Different coding algorithms are used for speech and audio, and ACELP is used for speech and audio. Amr-WB + has the same effect on Audio Encoding as he AAC + at a low bit rate. Amr-WB + contains Amr-WB, but the complexity is higher.
There are three types of frames:
Rfc3267 references: http://ietfreport.isoc.org/rfc/PDF/rfc3267.pdf
Amr if1 frame format:
Amr if2 frame format
