Data usage difference on channels

[dinkyyy99]

Tweet

Disregarding the itv1 hd channel
Is it possible to record different data usages on the other channels? Tested bbc1, ch4, and itv3 for 4 minutes each and got 12mb, 14mb and 17 mb respectively,
I thought I would have got a very similar ammount for each channel
Using http://iPhone.tvcatchup.com with an iPhone 4

[Belladonic]

Your question was answered last night in your other thread. Between 275 and 320kb/s. If you have a problem with data usage, don't use mobile devices.

Now go back to your other thread, use the data given to you, and divide your usage by the time you were on site. That will tell you what you are streaming at.

When on wifi streams are 360, 720, 1024, and 3000kb/s respectively for lo, standard, hi, and HD

[dinkyyy99]

No with due respect it wasn't answered in my other post ( incidentally my question last night was only half answered )
This is s completely different question. I'm asking is it normal to record different data usages with different channels

[Belladonic]

Are you timing EXACTLY the amount of time you are on a channel?

Data transfer on mobile devices is between 250 and 320k/s.

Try your calculations again using a stopwatch to ensure an exact measure and let us know your findings. Any discrepancies in data transferred I would say is down to the length of the pre-roll advert as some are 15s, and others are 30s, so you could easily have something like 20seconds of extra data transferred just on the pre-roll. Start your timing before the pre-roll. And allow a slight discrepancy for natural fluctuation in bandwidth.

Going back to length of pre-roll, a 15 second discrepancy increases data (assuming a 300k speed) by 4500kb

[TVC_James]

video encoding is VARIABLE bit rate, we specify a target bit rate but it may go above and below this depending on picture complexity. Whereas most TV is constant bit rate so a lot of the time bandwidth is wasted but at other times there's insufficient bandwidth for the image complexity (this is when you see "blocking") but given satellite bandwidth is sold assuming constant bitrate this is why satellite is constant bitrate, and we're variable bitrate as it delivers better quality per bit of data transferred.

[Belladonic]

variable being what I implied when I said 'natural fluctuation'

Assuming a 300k constant (or average speed) a minute chews up 18000k of data, or 140mb an hour

[dinkyyy99]

Thanks for the comments. Done some more tests and nearly all the channels use 4 mb ish per minute
And bbc1 uses 3mb ( or slightly less)
Was just curious why bbc1 specifically uses less
Over an hour it's 70 mb less than other channels,

[Belladonic]

Interesting...