By default, a popular FFmpeg codec library is used to handle AAC sound on server. This codec provides good sound quality and coding speed, but it can fail on some AAC frames, type 0 for example.
As alternative, another popular Fraunhofer codec library can be used in WCS.
В связи с этим, в WCS предусмотрено использование другого популярного кодека Fraunhofer. When sound quality comparable to FFmpeg or, in certain cases, higher this codec provides higher performance. Besides, Fraunhofer codec correctly works with frames on which FFmpeg fails.
To enable Fraunhofer AAC codec usage, set the following parameter in flashphoner.properties file:
use_fdk_aac=true