'Stats for nerds' _How does the frame resolution presented relate to the camera's resolution? - AVS Forum
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post #1 of 5 Old 10-18-2013, 06:04 PM - Thread Starter
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If you are looking at a Youtube video and right click the mouse on the video, a selection box appears. Click "Stats for nerds' and information about the video appears in the corner of the Youtube. I assume that applies to the Youtube video being played.

I am trying to understand how the video resolution information presented on the YT video relates to the resolution of the camera that recorded the video. Youtube may compress the camera's video file and otherwise modify it.

After looking at a few videos from high speed video cameras once the resolution seemed to correspond exactly to a camera resolution for the high speed video but other times it does not. ??

Maybe Youtube and the cameras select from a limited number of resolutions and sometimes they happen to be the same?
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post #2 of 5 Old 10-19-2013, 06:07 AM
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Not easy to follow this question and I think the reason is you're using the terminology wrong. Resolution refers to the size of the picture in terms of dots or pixels.
Example:
1080p: 1920x1080
720p: 1280x720
480p: 854x480
360p: 640x360
240p: 426x240
Youtube simply provides a means of changing (downsizing) the resolution to better fit your connection speed. If you don't have a high speed connection then you want to downscale the resolution to get a more constant playback without a lot of pauses (buffer empty interruptions).

I *THINK* what you're talking about (and please correct me if I'm wrong) is video compression (bit rate) or the amount of detail being read in a given second in time usually stated as Kb/s or Mb/s. That can be a bit complicated since some cams shoot vbr and others cbr.

CBR (Constant Bit rate) records at roughly the same bit rate from start to finish regardless of what is being shot. So if the cam is rated at say... 24Mb/s, then it record at 24 even in darker slower scenes where that much information is not really required.

VBR (Variable Bit Rate) is a different animal and does not necessarily record at the rated bit rate of the cam. VBR has the ability to automatically vary the bit rate according to what is being shot. If you are shooting a slower, darker scene for example then the highest bit rate your cam can shoot at may not be required so the cam scales down the bit rate to something a bit more reasonable and less space wasting. To the other extreme, if you are shooting something fast and bright then vbr has the ability to increase the bitrate to avoid a loss of quality.

So in other words... long story short... the fluctuations you see could very well have nothing to do with youtube and simply coming DIRECTLY from the cam itself if it's shooting in a vbr mode (and I think most do now). This is all assuming of course the video is coming directly from the cam and not edited. Editing and rendering are a different ballgame altogether since the editor also has the ability to re-juggle the bit rate.
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post #3 of 5 Old 10-19-2013, 08:15 AM - Thread Starter
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This is a special case involving high speed video that does not involve bit rate.

For high speed video, affordable cameras record at high frame rates with reduced resolution - high bit rate recording. The cameras, that I am familiar with, process the high frame rate recording to produce a 30 fps output video file with the same low resolution used for recording - low bit rate video playback file.

For example, a Casio Ex FH20 records at 210 fps with 480 X 360 resolution at a high bit rate. It produces a video file of 30 fps and 480 X 360, a low bit rate video file. When played back at 30 fps the motion is only 1/7 speed of the true motion, = 'slow motion'.

I would like to identify the unknown cameras used for Youtube slow motion videos or at least get an idea of which cameras might have been used. Is the 'Stats for nerds' at all useful to help ID the camera?

Case I - Resolutions seem to match.

http://www.youtube.com/watch?v=tIHDA5bgZqM
Right click on the video and select 'Stats for nerds'. You will see 480 X 360 on this video. I believe that the high speed video camera that produced this video is probably the Casio FH20 because it records with the same 480 X 360 resolution. Is that a reasonable association?

Case II - Resolutions don't match.

However, when I look at this second Youtube video, where the recording camera is stated to be a Casio FH25 at 240 fps that records 240 fps with resolution of 448 X 336, there is no relation between the recording resolution and the 'Stats for nerds' resolution. ?

http://www.youtube.com/watch?v=hzNQMhyuXd0
'Stats for nerds' on this video shows a resolution of 854 X 480. That resolution does not appear to be related to the recording resolution of the FH25, 448 X 336.

BTW - this is one of the best close up videos of a golf ball impact that I have seen produced with the affordable HSV cameras- the Casio cameras with very fast shutters (to 1/40,000 second).
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post #4 of 5 Old 10-19-2013, 01:37 PM
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Quote:
Originally Posted by Chas Tennis View Post

'.

I would like to identify the unknown cameras used for Youtube slow motion videos or at least get an idea of which cameras might have been used..
I think you're relying TOO MUCH on the notion that all these videos are directly from a cam and do not go through an editor where you can change frame rates, resolutions, bit rates... etc to something completely different from what that cam shot.
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post #5 of 5 Old 10-19-2013, 01:44 PM - Thread Starter
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Since I have two different results already that seems to be the case. I did want to research the problem to see if I could learn anything useful or interesting.
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