Does AudioTrack buffer need to be full always in streaming mode?

I'm trying to figure out some latency issues with the Android AudioTrack, and documentation is very scarce. Two question I have in particular are

1. Does an AudioTrack object need its buffer full before it starts playing audio, which would indicate that minimum latency one can get in (minimum buffer length) / (sampling rate)? Does it alternatively start playing immediately the first chunk of samples have been gi开发者_StackOverflow中文版ven to it? Is there a way to check how full the buffer is before it starts playing?

2. Secondly, when exactly does AudioTrack block?