Screen Capture Problem

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I have two machines, both XP SP3.

I have tried a few screen-capture softwares, e.g. DEBUT, CAMTASIA,
SNAGIT, AVS.  They all fail to capture sound - just video. on machine
1, but two of them, at least, work fine on machine 2.

I figure the problem may be  the video card.  Am I right?  Anyway the
video cards are  (I have included other info for the two machines):

machine 1

machine 2
AMD Athlon 64, 2200 MHz (11 x 200) 3200+

Okay, so should I replace the video card in machine 1?  If so, how can
I know what card will work  (what is the pertinent spec)?  Tell me
what to buy?  

I have read on Google that this is a problematic area - some cards
seemingly will not pass on the audio without some trick such as
patching audio speaker out to line in or mic in, which I have tried,
without luck.




Re: Screen Capture Problem wrote:
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I agree it is a problematic area.

Don't go off and buy anything just yet.

You need to understand some of how the process works, to understand
why buying more hardware won't help. I'm not an expert on capturing
content, but this gives the basic idea.

    file           --+-- CODEC ---- decoded video (annotation plane or
    (or stream)      |                             frame buffer plane or
    DRM protected    |                             surface used for 3D rendering)
                     +-- CODEC ---- decoded audio --- Sound card ----+-----
    Captured audio <------------- Audio recording <------------------+ "What you
    file                          program                               Mixer
feedback path

Programs that copy content, can work at the file level (just after
the DRM step), or they could capture the info just after the CODEC
decodes the information into something useful. Windows has ways of
attempting to protect against copying media while it is in memory.

Eventually, the content is delivered to the video card (for the image portion).
And the sound content is sent to the audio card.

The video card has at least three places to hold image data. To you and I,
it looks like it's "just a screen". But the components on the screen
are composited, like pasting items in a collage. A still image, can
be stored directly in the main frame buffer. Video content, was at one
time place in the annotation plane (now VMR7 and VMR9 are used instead).
And when you play a 3D game, the buffer used for that, can be separate
as well. They're all glued together, to make the final image.

This means, for a program attempting to "screen capture", it has to be
prepare to handle all three kinds of buffers. If a method lacks all
three, there can be a colored square where the image should be, when you
look at the captured content. An example of a reasonably well equipped
physical level capture program would be FRAPs. Another might be
Camtasia, but I don't know it's capabilities right off hand.

Audio capture can be attempted as well. On older hardware, there
was a mixer path that was called "What you hear". Effectively,
it loops the stereo output back to the stereo ADC input, for capture.

More recent OSes, there have been rumors of the demise of that path.
The hardware may still have the capability, but it would be possible
for the OS to prevent its usage.

What you'd need to try in such a case, is use the custom mixer panel
that comes with the sound card, and see if you can enable the tick
box for "What you hear", also known as "Stereo Mix". My custom mixer
panel looks like this. And the green button at the bottom of
"Stereo Mix", has enabled that as an input. If I use the Microsoft
"Sound Recorder" program, I can record sounds coming through the front
speakers of the sound system.


So far, we haven't discussed buying any hardware. Since much of the
restrictions are software based, there wouldn't be much point.

Even if your mixer panel doesn't have a "Stereo Mix", it might well
be present in hardware. Just not accessible.


It is possible for video and audio to travel over the same cable.
The HDMI interface on computers, has room for both video and audio.
And on modern equipment, you can have a confusing "digital output"
option, which causes the sound to travel over the HDMI cable. Depending
on your "Home Theater" setup, such a path may not line up with how your
theater is wired. Some people have a separate audio amplifier with
analog inputs. In which case, you'd want to switch the computer
to using analog sound output, which is a separate audio device. But
this little distraction, has virtually nothing to do with capture.
As the best places to implement capture, are still inside the
computer. While I know of devices to capture HDMI (unencrypted,
less than 1080p), none of them as far as I know, could extract
digital audio. Redirecting the audio elsewhere, will make
capture easier.


Re: Re: Screen Capture Problem

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Thanks again, Paul.

I guess I should be thankful I was lucky enough that it worked on the
one machine, which I can continue to use of course.  It's just that I
use it in conjunction with AVS, which by bad luck mostly, is installed
on the other machine.  AVS insists that I buy another copy of their
software rather than allow me to remove it from the problem machine,
and transfer it to the machine where I need  it - where I can do a
good 'capture'.  .  IOW, they sell a license by machine not by use.
This means of course if I buy another machine, I must buy another
license.  Most software I know about would allow what I want to do.

bu hao



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