Have you ever tried to do a screen capture while playing a video. Press “print screen” key to take a screen shot, but eventually you are gonna end up with a black area where the video was originally present on the screen. DO NOT get frustrated that you can’t get a snapshot of the video you were playing, you can do something more amazing with that screen sot you just took! Read on if you want to do a little fun experiment with that image.
Here are the two videos I took. The Desktop Properties dialogue is opened to so that you can be sure the video is actually played in the background. The first video shows Kung Fu Panda being played as my desktop background. The second video has the same movie played inside an image file.
Here are the steps you should do to get the desired effect –
- Play a video player of your choice (VLC, Windows Media Player, GOM Player, WinAmp..)
- Press the “Print Screen” Key on your keyboard. You can do it in full screen or normal mode
- Paste (CTRL+V) into your image editing program such as Paint (WIN+R»mspaint)
- Save the image to your hard disk. You can save the image as PNG, TIFF or BMP
- GIF, JPG and low quality BMP does not work
- Open the image using any of the available image viewers such as Windows Picture and Fax Viewer (Windows Gallery) or IrfanView
- Play a video and maximize the video window Make sure you play the video using the same layer you used in step 1
- Goto the open image and… Voilà the video being played can be seen in the image!
If you want to know why you can’t take a screen shot of a video played read the following section. Else skip to the next topic.
Video screen capture. Why NOT?
So why can’t you take a screen shot of a video player or a DVD video decoder by just pressing “prt-scr”? The reason lies in the method video is displayed on your monitor, or rather the video is send to your monitor. After explaining this a small trick to get a screen shot of video is also mentioned.
To understand why a video can’t be just screen shot, we need to know how a video is normally displayed. You would probably have heard Hardware Acceleration or Hardware acceleration layer if you are into computers or gaming. Hardware acceleration is a technique used to make video processing faster. In Computers the CPU used is a general purpose CPU that means it is not designed for a specific purpose. an example of a operation specific CPU would be that of a DECODER IC seen in a DVD player. The Rule Of Thumbs being anything running on specialized hardware is much faster that the same process implemented in software. This is one of the reasons why your top end Music player uses decoder ICs and produces better sound reproduction than your normal PC. (For the most simplified explanations read the wiki articleson RISC and CISC)
Computers today use some hardware to decode the video rather than use software decoders. This is because of the high bandwidth required by video streams. So while your desktop (as a bitmap image) is saved in the computers video memory and then send to the monitor, the video you see is not! Video is processed by the hardware, then bypassing the video buffer (memory) and overlayed on to the signal that comes out of the Video RAM, going to your monitor. That is a form of signal mixing. To know eher to display the video a technique called colorkey is used to selectively replace a specified pixel color (usually near-black or magenta) with video content. A colorkey pixel present in the computer graphics video, will be replaced by video from the hardware accelerator.
When you press Print Screen, your OS copies the bitmapped data stored in the video memory to your clip board. When playing a video if you do prt-scr all you get will be the colorkey pixels instead of the picture shown on the video! That is why its all black.
Take a Video Screen shot!
There are several methods to take screen shot from a video. Here are the easier ones.
- set hardware acceleration to none (see image Play the video in Windows media Player and press Print screen
- Play the video in VLC player, take a screen capture using menu Video»Screenshot
- Drag the video to Windows Movie Maker ( WIN+R»moviemk ) click play on the player at the far right corner. Pause at the required frame and goto Tools»Take Picture from Preview