Minimum 4.4 Mbps required for "near-instant" streaming of HD videos?

Question

There have been several threads and posts on this forum with Apple TV (gen 2) users complaining of having to wait hours before being able to watch a rented HD movie or TV show.
I suspect that, in order to get the HD movie or TV rentals to start playing within the advertised 20-30 seconds, you need to have actual high speed internet bandwidth of at least 4.4 Mbps. Here's why I think that:
I rented "No Ordinary Family" for free on iTunes on my computer, so I could see how big the HD file actually is.
The file is 1.44 GB for a 43 minute, 54 second show in H.264 HD, 720p. (you can find all this out by right-clicking on the movie in the "rentals" sidebar category in itunes, and selecting "get info", then "summary".)
So the duration of the show is 2,634 seconds.
1440 MB / 2634 seconds = 0.547 MB per second.
Convert that to bit rate (1 MB = 8 Megabits, or Mb):
0.547 MBps = 4.374 Mbps.
Now, in order to get near-instant streaming of this HD content, your actual bandwidth has to be higher than the movie file's bit rate. IE: you have to be able to download the file at a faster bit rate than the file takes to play.
Thus, I submit that, based on the data properties of a real itunes HD rental, in order to get near-instant real-time streaming, you would need a sustained bandwidth of 4.374 Mbps or higher.
This could explain why anyone with actual (not necessarily "advertised") bandwidths below 4.4 Mbps are not getting real-times instant streaming without having to stop and wait every now and then. I'd bet that even people who have "up to 6 Mbps" probably have actual bandwidths that drop below 4.4 every now and then, causing the "hiccups" in HD streaming performance.
Using myself as an example, I pay for "up to 3 Mbps" DSL, but on average I get something between 1.5-2.5 Mbps. Also, any other activity on your network (spouse surfing the web or kid playing an online game while you're streaming an HD movie on apple tv) would reduce the amount of available bandwidth for the HD stream.
My response has been to order faster high-speed internet ("up to 10 Mbps"), which will be installed next week. It's only an extra $5/month for me, and it should help to make sure the youtube and video podcast performance is much faster than it is right now, and I should get the true HD version of Netflix content as well, which I'm not now.
However, it does not explain why some people on this forum who claim to have 12 or 14 Mbps are having a similar problem. I am convinced it is the primary problem for me, though, since it's not just my HD rentals, but my video podcasts that I have to wait a long time for, and the YouTube videos take a bit of time as well, depending on their quality. Netflix is available quite quick, but I usually get quality I'd say is equivalent to DVD (480p) at best, and typically SD.
Does anyone have an experience that supports or contradicts this hypothesis?

Answer 1

dgalvan123 wrote:
I suspect that, in order to get the HD movie or TV rentals to start playing within the advertised 20-30 seconds, you need to have actual high speed internet bandwidth of at least 4.4 Mbps. Here's why I think that:
Now, in order to get near-instant streaming of this HD content, your actual bandwidth has to be higher than the movie file's bit rate.
Absolutely correct - it's obvious when you think about it - trouble is the advertising blurb makes people assume they get instant video.
IE: you have to be able to download the file at a faster bit rate than the file takes to play.
Yes, and if the rate is slower then it'll buffer an adequate amount of video internally before starting, so that there's enough of a head-start that the slower feed will never run out before teh end of the movie assuming that rate is sustained.
Thus, I submit that, based on the data properties of a real itunes HD rental, in order to get near-instant real-time streaming, you would need a sustained bandwidth of 4.374 Mbps or higher
Your figure is fairly specific to that movie - not all movies will be encoded at the same bitrate - some will be higher, some lower.
This behaviour is nothing new and parallels AppleTV 1 exactly, again the advertising makes people think it's doing something new and clever,it's not.
As an example, with AppleTV 1, as I have a slow connection of 1 Mbps, I would rent on the morning or night before I wanted to view a rental to allow it to fully download, or at least for enough to download and play through without interruption.