FMOD2.02.05 version is used in UE4.27.
First, I call the following code and set it to silent mode:
Then, I use the
setSoftwareFormat method to explicitly specify the sampling rate of 48000;
I added a DSP callback, and calculated the delta time(in milliseconds) between current callback and the last callback. The results are as this image.
During the playback process, the time interval at which the callback function is called suddenly decreases, and it stays at this level. It is irregular, sometimes it is very low at the beginning of the playback, and sometimes it suddenly decreases after tens of seconds of playback.
I am sure that this happens only in FMOD_OUTPUTTYPE_NOSOUND mode. I set FMOD_OUTPUTTYPE_NOSOUND to simulate the situation where there is no audio device on the computer.
This problem causes the audio PCM rate I get from the DSP callback to be unstable and Uneven.