I have an MPEG-I that I made myself.  I wanted to screen grab a frame from it to
share with someone in a letter.  I was unable.

With several viewing applications, when I screen-grabbed the playing animation,
I ended up with a blank screen in that part of the window that was showing the
animation.

Q: Is this DRM, in the sense that someone made them set up movie players that
way, or is it an inevitable and unintended function of the way computers handle
moving vs. still images?

I had always assumed it was DRM when I couldn't screen grab a frame from a
store-bought DVD played on Windows XP; but I see it so often on all my linux
apps that I'm guessing it's just the technology.

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gregjohn wrote:
> Q: Is this DRM, in the sense that someone made them set up movie players that
> way, or is it an inevitable and unintended function of the way computers handle
> moving vs. still images?
> 
> I had always assumed it was DRM when I couldn't screen grab a frame from a
> store-bought DVD played on Windows XP; but I see it so often on all my linux
> apps that I'm guessing it's just the technology.

	Not DRM. I don't know the details, but it's a function of the video 
driver. If the rendering is done via hardware, then the usual screenshot 
won't work. If you have a software renderer, then it will.

	I think some good players have an option to take a screenshot - where 
they ensure it'll get one even if you're using a hardware renderer.

-- 
If a mute swears, does his mother wash his hands with soap?


                     /\  /\               /\  /
                    /  \/  \ u e e n     /  \/  a w a z
                        >>>>>>mue### [at] nawazorg<<<<<<
                                    anl

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Mueen Nawaz wrote:

>     Not DRM. I don't know the details, but it's a function of the video 
> driver. If the rendering is done via hardware, then the usual screenshot 
> won't work. If you have a software renderer, then it will.

Some thing with 3D computer games. Because the data doesn't exist in the 
framebuffer but is composited in in hardware, copying the framebuffer to 
a file won't capture that data.

Depending on the specifics, there *are* ways to do this though. Just the 
standard screen capture won't do it, that's all.

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gregjohn <pte### [at] yahoocom> wrote:
> Q: Is this DRM, in the sense that someone made them set up movie players that
> way, or is it an inevitable and unintended function of the way computers handle
> moving vs. still images?

  It's frame buffer optimization. Nothing to do with DRM. This feature has
existed for long before DRM was even an idea.

  The player (usually using DirectX, or in Linux by using the video driver)
is not drawing the video on your screen memory at all, but to a frame buffer.
A frame buffer is a separate chunk of RAM which has been mapped to the
video card by the memory bus.

  In the actual screen memory the pixels in the area where the video should
appear have a certain color. When the video card detects pixels of that
color inside that area, it will substitute them with the contents of the
frame buffer instead. (This allows even the screen to have a different
bit depth than the frame buffer, which allows eg. having your screen to
be in paletted 8-bit mode, while the video player is showing the video
in full color mode.)

  When you make a screen capture, you are simply capturing the screen memory,
and thus you are only get those specially-colored pixels. The screen capture
routine knows nothing of frame buffers.

  You can turn this frame buffer optimization off, after which the screen
capturing becomes possible. In Windows there is a setting somewhere which
you can use to set the level of video acceleration. Lower it until you can
screen-capture your video. (Obviously screen refreshes may become quite
sluggish.)

  If you are using mplayer in linux, simply play the video with -vo x11
and you'll be able to screen-capture it. (The x11 driver does not use
hardware acceleration.)

-- 
                                                          - Warp

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"gregjohn" <pte### [at] yahoocom> wrote in message 
news:web.48d1af5b4e31f5f434d207310@news.povray.org...

>I have an MPEG-I that I made myself.  I wanted to screen grab a frame from 
>it to
> share with someone in a letter.  I was unable.


      Have you tried Fraps? Map a key in the screenshots section, open your 
MPEG and hit pause quickly (or play it until just before your desired shot). 
Then open Fraps, play your MPEG, and hit that key when you want. You can 
also set it to take screens at timed intervals like every 30 seconds or 120 
seconds, etc.

     This is the free version I'm talking about. This will give you a small 
Fraps watermark at the top of the screen if recording a video of your MPEG, 
but you don't get this with screenshots.

      ~Steve~

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St. <dot### [at] dotcom> wrote:
>       Have you tried Fraps? Map a key in the screenshots section, open your 
> MPEG and hit pause quickly (or play it until just before your desired shot). 
> Then open Fraps, play your MPEG, and hit that key when you want. You can 
> also set it to take screens at timed intervals like every 30 seconds or 120 
> seconds, etc.

  Does it understand frame buffers and is it capable of capturing them?

-- 
                                                          - Warp

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Warp wrote:
> St. <dot### [at] dotcom> wrote:
>>       Have you tried Fraps?
> 
>   Does it understand frame buffers and is it capable of capturing them?

It's marketed as being for doing screen captures of games, which due to 
their utilisation of your 3D hardware also don't usually capture 
properly. But IDDQD...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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"Warp" <war### [at] tagpovrayorg> wrote in message 
news:48d294e2@news.povray.org...
> St. <dot### [at] dotcom> wrote:
>>       Have you tried Fraps? Map a key in the screenshots section, open 
>> your
>> MPEG and hit pause quickly (or play it until just before your desired 
>> shot).
>> Then open Fraps, play your MPEG, and hit that key when you want. You can
>> also set it to take screens at timed intervals like every 30 seconds or 
>> 120
>> seconds, etc.
>
>  Does it understand frame buffers and is it capable of capturing them?

      Explain to me what a 'frame buffer' is, and I'll try to answer that. 
:)


       ~Steve~



>
> -- 
>                                                          - Warp

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St. <dot### [at] dotcom> wrote:
>       Explain to me what a 'frame buffer' is, and I'll try to answer that. 

  I already did in another post in this thread.

-- 
                                                          - Warp

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"Warp" <war### [at] tagpovrayorg> wrote in message 
news:48d2a590@news.povray.org...
> St. <dot### [at] dotcom> wrote:
>>       Explain to me what a 'frame buffer' is, and I'll try to answer 
>> that.
>
>  I already did in another post in this thread.


 Yep, I see it. Well, I don't think frame buffering comes into this with 
Fraps. If you 'record' say, a vid of your own custom-made Crysis map, then 
Fraps will record it as it happens within the game itself. If you have a 
game that is stuttering on a low-end comp, Fraps will record that 
stuttering, and vice-versa.

     No idea where frame buffering comes into this scenario.


      ~Steve~


>
> -- 
>                                                          - Warp

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