Re: [Discuss-gnuradio] USRP Delay Measurements

[Thomas Schmid]

Hi Eric,

I did some calculations and something doesn't add up. As I mentioned
in my last email, I am using usrp.sink_s. Thus, my samples are real
shorts (16 bit). I verified the buffer size by printing out the buffer
allocation size in gnuradio-core/src/lib/runtime/gr_buffer.cc. The
size is 32KB.

If I am using an interpolation factor of 400, then my sample rate
should be 128M/400=320k and thus the USB speed should be
320k*2B=640kB/s. With this number, the estimated delay for a sample to
pass through the buffer should be 32k/640k=0.05s. The problem is, that
I measure about 28ms. I think I shouldn't complain, since in reality
the system is faster than what I calculated. Though I still would like
to understand what's going on ;)

Thomas