Degraded G.726 quality with pops and clicks

[BrainLai]

When streaming G.726 24/32Kbps, I found the quality is degraded and unacceptable compared to AWave studio(play the saved audio bitstream).

For G.726 24Kbps, the sound is filled wih pops and clicks.
For G.726 32Kbps, a young man sounds like an old one.

Does it result from ffmpeg?

If it does, could you please tell me the corresponding ffmpeg source version and how you build it (that is, the configure line arguments).

PS:
1. The VLC version is 0.8.5 (0.8.6a has the same problem).
2. The audio encoder is ITU reference implementation.

Regards,
Brain Lai