Internet radio data download calculations

John_Gray

If I listen to a 128 kbps 'internet radio' data stream on my PC, I expect this to require a download data transfer rate of roughly 16 kBytes per second.

However, in Task Manager -> Networking, if I set up an column item for "Bytes Received per Interval" and let the Update Speed default to Normal, this gives me a fairly consistent value of about 66-68 kBytes for each roughly-2-second interval, or 33-34 kBytes per second.

This is slightly more than double the first figure, and whereas I would expect some overhead for the data transmission, over 100% seems a bit much!

Have I miscalculated, or could someone explain why the figures are so different?

Thanks!

superscaper

My complete off the top of my head guess may be splitting it into stereo (128kbps for each of left and right) but that doesn't really seem right either. Are you sure that no other processes are taking up bandwidth. God knows how many automatic updaters etc are always checking things online on my PC. But as you've pointed out it would have to be something that is constant. Does it indeed go down to approx zero when you stop the radio streaming?

John_Gray

I would be very surprised if the 128 kbps data rate was a per channel figure, but I must admit that it had never occurred to me as a possibility!

You are correct in your assumption that my figures are for when I have nothing else running, and that when I terminate the internet radio stream the data rate goes down to almost exactly 0!

I may install DUMeter to see if Task Manager is telling me porkies... Unless someone can point me to a free equivalent which works on cable?

Would not one of those ISPs which implement capping know the answer?

superscaper

John_Gray wrote: »

Would not one of those ISPs which implement capping know the answer?

Cynical old me would say that would require a certain level of technical competance and expertise rarely found with ISPs.

It is a head-scratcher and I know the per channel thing doesn't sound right but that's usually the instinctive thing to say when you get a doubling or halving in rates from what you expect. But I'm sure it must be something else.

bat999

Hi
I don't think that streaming radio is like downloading (say) a file of data.
I don't think that it fires bits at you at a rate of 128000 per second.
I think that when you are listening to the station it sends 'packets' of data for you to fill a buffer with. Like a reservoir.
Then the media player processes (empties) the buffer at a particular bitrate. The station just has to keep topping up the buffer to make sure that there's enough there for you to process at that bitrate without running empty. So sometimes you get lots, and sometimes you might get little or none.
Maybe if you measured it over a longer timescale you would get a more realistic value. Perhaps those few seconds that you have measured previosly were very busy ones and there may have been others afterwards when nothing was being downloaded at all.
That's my take on it anyway.
:cool:

John_Gray

I see what you are saying, but even if the data is packetised, then there will be an "average data rate" required to keep the sound going.

In Task Manager -> Networking the green line is almost exactly flat, for at least half an hour at a time (not just a few seconds)!