How does Google evaluate the content of a Youtube video?

[aristotle]

Recently, in doing a Google search on a single word (call it "widget"), a Youtube video appeared in the number 3 position in the SERPs. When I looked at this video, it was nothing but a sequence of photographs accompanied by some classical background music.

THERE WERE NO SPOKEN OR WRITTEN WORDS on this entire video, and as far as I could judge, the photos had no connection to the search word (widget). The only connection was the video's title (Widget), which obviously is an exact match.

Here are my questions:

1. How can this video rank in the number 3 position for "widget" when its only connection to that word is its title?

2. How does Google determine the content of a video? Does it have a program that somehow analyzes the video and evaluates its content, even when there are no spoken or written words, as in this case. Or does a Google employee actually watch the video and personally evaluate its content?,

[tedster]

There are a number of signals Google can use, even with a "wordless" video. The obvious one is the Title of the page where it's embedded. Then there's popularity - how many other sites link to it? how many other sites embed it?

There's also the possibility of embedded meta data in the file that may provide a few signals at a lower level.

[tedster]

Another educated guess - the number of views as well as comments collected could be another signal of popularity that the algo taps into.

[aristotle]

Thanks for your replies.

However, despite the possible use of these other "signals", it appears to me that Google has made a serious error in giving this video a number 3 ranking, because it doesn't contain any information relevant to the search term.

I believe this example may reveal a major flaw in the way Google ranks videos. since it is apparently giving many of them high rankings without knowing what is actually on them.

To illustrate the risk in this approach, imagine a hypothetical case in which someone creates a #*$! video and gives it the title "Alice in Wonderland". Also imagine that this person embeds this video on a page called "Alice in Wonderland", creates external links with that anchor text, etc. Then unless Google has a way to directly check its content, a child searching for "Alice in Wonderland" might see this #*$! video at the top of the SERPs and click on it.

In other words, if Google is merely using titles and "external signals" as the basis for its evaluation, in some cases this may not be adequate to determine what is actually on a video. And if they don't know what's actually on it, they are taking a major risk in giving it a high ranking.

Google would never give an ordinary web page a high ranking without dirctly checking its content? So why is it giving videos high rankings without directly checking their content?