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Hi All,

I'm trying to use wireshark to check the buffering time for a youtube video. I was thinking that, the buffering time started from GET /watch?v=LNMWgmvdLws HTTP/1.1 but i cannot identify which message said the video start to play.

I need help for that. Thanks in advance!

BR

asked 28 Nov '12, 01:18

Djo's gravatar image

Djo
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You won't be able to find that info in the network trace, as the buffering will be done by the YouTube app once the data comes in. It will then use a specific buffering time to make sure a constant video stream can be shown, even when there is a little jittering or packet-loss (resulting in retransmissions). How YouTube decides what time to use for the buffering, I don't know.

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answered 28 Nov '12, 02:18

SYN-bit's gravatar image

SYN-bit ♦♦
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accept rate: 20%

As @SYN-bit said, there is no good way to find that in the protocol, as it's one data stream. However, I asked myself, if there might be some pattern in the packet flow, that correspond with the buffer time and I believe I have found a weak relationship.

I started your video two times and measured the time it took to buffer (start the video) with a stop watch. Then I looked a the IO Stats for those connections and found this.

alt text

alt text

To me it looks like the player first (almost totally) fills to buffer and then it starts to play. The time where the packet rate drops (you can only see it in 0.01s resolution), matches more or less the time I measured with a stop watch. So, the start of the first large gap in the IO graph is more or less where the video starts to play.

As I don't know how the player works internally, I can only call this a weak sign for the initial buffer time, but that pattern repeats in all tests (so far).

Regards
Kurt

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answered 28 Nov '12, 04:52

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Kurt Knochner ♦
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accept rate: 15%

edited 28 Nov '12, 04:59

1

Nice one, Kurt!

(BTW, where do you find the time :-))

(28 Nov '12, 05:38) SYN-bit ♦♦

Nice one, Kurt!

thanks.

(BTW, where do you find the time :-))

I sleep only 2 hours per day ;-)) And for interesting problems, I always find some time :-)

(28 Nov '12, 06:49) Kurt Knochner ♦
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question asked: 28 Nov '12, 01:18

question was seen: 3,510 times

last updated: 28 Nov '12, 06:52

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