What's the usage of group option when streaming out?

[marcofreda]

group=<amount of packets> to sent packets by burst instead of one by one
The text above is cut from streaming-howto-en.pdf.
I want to know the more detail about group option.
For example I have a file with 2048kbps. When I use a streaming client to watch it, I will get a avg rate 2048kbps on throughput.
But, exactly I get a burst rate in the starting phase, this behavior is caused by group option.
Is it right?
If I set value of group option to more number, the burst rate will keep more period.
Is the purpose of this option to put the client buffer up as soon as possible?

Thanks

[marcofreda]

What is the default value of group option?