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For example assume I have 2 video files of similar length while the first one is 100Mb and the second one is 30Mb. Does the 30Mb one will load faster on Youtube?

NOTE: I'd like to know for sure, not assumptions.

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closed as off topic by slhck, random May 31 '12 at 16:14

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1 Answer 1

up vote 3 down vote accepted

While I know you'd like to know this for sure, no one knows except those who implement the buffering at YouTube's backend. At our institute, we also evaluated various buffering scenarios, specifically targeted toward YouTube streaming. So far, the buffering model seems to be highly influenced by factors you can't estimate – with influences of the actual video bit rate and the download link bit rate.

In general though, the YouTube buffer first of all works based on time, not on data. It seems there is a buffer of around two seconds that will be filled first, then the video will be played.

In your specific case, a 10Mb (Did you mean Megabit?) video will not be buffered faster than a 30Mb video. It rather depends on the speed of your internet connection.

If you'd like to know more about YouTube QoS and QoE, I redirect you to the publications of:

  • Tobias Hoßfeld (Universität Würzburg, Germany)
  • Thomas Zinner (Universität Würzburg, Germany)
  • Raimund Schatz (FTW Wien, Austria)

See this technical paper, especially section 2.3.1 (Influence of Video Bit Rates) and the conclusion:

Tobias Hoßfeld, Raimund Schatz, Thomas Zinner, Michael Seufert, Phuoc Tran-Gia,
Transport Protocol Influences on YouTube Videostreaming QoE, 2011

This stalling pattern is non-trivial, due to a number of interactions and correlations on several layers of the ISO/OSI stack. YouTube implements flow control on application layer; TCP implements flow control on transport layer; the video player implementation tries to overcome stalling by means of a video buffer; and the videos are encoded with variable bit rates. However, we found that the stalling patterns can be modeled in the following way: the stalling frequency as ratio of the number of stallings and the video duration simply depends on the normalized video demand, which is the ratio of the video bit rate and the bottleneck link capacity.

However, their relation follows a non-linear exponential function. The median of the length of a single stalling event was found to be between two seconds and four seconds. With these two parameters, the observed stalling pattern can be modeled for a given bottleneck bandwidth

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Thank you for your detailed answer, it is very much appreciated! Regarding the "10Mb", it's a typo. I actually meant 100Mb, which is MegaByte.. –  Eugene S May 31 '12 at 16:23
Glad to help! By the way: Mb (with a lowercase "b") usually indicates Bit – If you mean 100 Megabyte, use "MB" instead. –  slhck May 31 '12 at 16:24
I'll remember that! :) –  Eugene S May 31 '12 at 16:39

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