Yes that is correct
sf::SoundBufferRecorder is not what you are looking for. If you want to do near real-time processing you need to derive from
sf::SoundRecorder. Then you can implement the
onProcessSamples() method, which will provide you with the samples at a specified rate. Take a look at
the doc or the implementation of
sf::SoundBufferRecorder. Also the VoIP example might show you a way how to do it.