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Old 11-05-2008, 08:46 PM
"Sean Carolan"
 
Default Check my math please

Ok this is kind of a goofy question but I want to make sure I get it
right. Suppose we have a 25 mb video, that is 117 seconds long. If we
wish for this streaming video to play smoothly with no compression,
buffering or skipping, the following bandwidth requirements must be
met:

25 megabytes = 204800 kilobits.

204800 kb / 117 seconds ~ 1750kb/s

Does that look right to you?
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Old 11-05-2008, 08:55 PM
"Neil Aggarwal"
 
Default Check my math please

Sean:

Don't forget that the data speed != line speed.
A line will only carry about 70% of the line
speed as data because of packet overheads.

Neil


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> -----Original Message-----
> From: centos-bounces@centos.org
> [mailto:centos-bounces@centos.org] On Behalf Of Sean Carolan
> Sent: Wednesday, November 05, 2008 3:47 PM
> To: CentOS mailing list
> Subject: [CentOS] Check my math please
>
> Ok this is kind of a goofy question but I want to make sure I get it
> right. Suppose we have a 25 mb video, that is 117 seconds long. If we
> wish for this streaming video to play smoothly with no compression,
> buffering or skipping, the following bandwidth requirements must be
> met:
>
> 25 megabytes = 204800 kilobits.
>
> 204800 kb / 117 seconds ~ 1750kb/s
>
> Does that look right to you?
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos

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Old 11-05-2008, 08:55 PM
John R Pierce
 
Default Check my math please

Sean Carolan wrote:

Ok this is kind of a goofy question but I want to make sure I get it
right. Suppose we have a 25 mb video, that is 117 seconds long. If we
wish for this streaming video to play smoothly with no compression,
buffering or skipping, the following bandwidth requirements must be
met:

25 megabytes = 204800 kilobits.

204800 kb / 117 seconds ~ 1750kb/s

Does that look right to you?




add 5 or 10% for network protocol overhead. I generally figure,
25Mbyte == 250Mbits, so come up with 2.1 Mbit/sec.





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Old 11-05-2008, 08:55 PM
Monty Shinn
 
Default Check my math please

Sean Carolan wrote:

Ok this is kind of a goofy question but I want to make sure I get it
right. Suppose we have a 25 mb video, that is 117 seconds long. If we
wish for this streaming video to play smoothly with no compression,
buffering or skipping, the following bandwidth requirements must be
met:

25 megabytes = 204800 kilobits.

204800 kb / 117 seconds ~ 1750kb/s

Does that look right to you?
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Sean,

The size of the file doesn't make much difference. What matters is the
resolution and framerate of the video.


Depending on the resolution and framerate, you probably won't be able to
stream realtime without some buffering and/or compression. And don't
forget, it isn't just the size of your pipe to the internet, it is also
the size of the recipient's pipe, and how many concurrent connections
you will have at the same time, assuming you are hosting locally.


Lower framerate and resolution = lower bandwidth required.

HTH,

Monty
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Old 11-05-2008, 08:59 PM
"Sean Carolan"
 
Default Check my math please

> Don't forget that the data speed != line speed.
> A line will only carry about 70% of the line
> speed as data because of packet overheads.

Thanks for pointing this out. I believe I have enough information to
make my case. My guesstimate before seeing the actual file sizes was
that this would never work with less than a 2Mb/s connection, turns
out I was pretty close!
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Old 11-05-2008, 09:06 PM
"Sean Carolan"
 
Default Check my math please

> The size of the file doesn't make much difference. What matters is the
> resolution and framerate of the vide

For a back-of-the napkin calculation can we not assume that data equal
to the entire size of the file will be streamed to the client during
playback? I understand that frame rate, etc. are important as well
but I do not need exact figures, just a general idea of what size
tube** is required on the viewer's side to see the video without
skipping.

** The internet is not really made of tubes. Unless you're from Alaska.
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