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ScreenPressor
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What is it?

ScreenPressor is a lossless video codec designed specifically for video screen capture (screencasts). It provides unprecedented compression ratio while keeping 100% of original information. Quality of lossless compression makes ScreenPressor perfect for use in online video conferencing and webinar applications. It's probably the best technical solution for video tutorials, presentations and instant screen (desktop) sharing. It's available as a codec or a library for Windows, Max OS X and Linux and can be used in most video recording and editing apps. Lossless video compressed with ScreenPressor can be watched in a browser using our free web player.

Lossless

Most popular video codecs are lossy, like DivX, H.264, VC-1 or Theora. They irretrievably dispose of information they consider unimportant to achieve desired compression rate. Providing acceptable quality for movies and video clips, lossy codecs perform visibly poorer on screencasts. Lossless codecs, like ZIP files, keep all original information intact. Here's a real example (note the size of compressed files):

Lossy compression (DivX, 970 kbps):

lossy compression

Lossless compression (ScreenPressor, 312 kbps):

lossless compression

Codec

A codec means compressor/decompressor and is not a standalone application but a component used by other applications. After installation, ScreenPressor is easily found in the codecs list available from all of your video capture and editing apps. Do not expect new icons to appear on a desktop or start menu (because, as mentioned above, video codec is not a separate program).

To create highly compressed screencasts with ScreenPressor you may use CamStudio (free), HyperCam or other video capture applications. Read more in tutorials section: how to record screen in CamStudio.

If you already have some captured video you can make its file size smaller by recompressing it without quality loss with ScreenPressor using for example VirtualDub (free). Read a step-by-step instruction on how to recompress video.

ScreenPressor version 1.1 and higher allow for a simple way to open codec settings directly: just run "\Program Files\ScreenPressor\spconfig.exe"

Compression

We compared ScreenPressor with popular lossless screen capture codecs as well as the most popular lossy codec (DivX, an MPEG4 implementation) on a set of typical screencast files. Each of sample video files was compressed with seven codecs. Also, for each video file, its compression with TechSmith Screen Capture Codec was taken for 100%. Results produced by other codecs were measured in relation to the TechSmith codec's compression results, also in percent. Comparison is summarized in a chart below. Since TechSmith is taken as 100%, lower percentage in this chart means better compression.

compression comparison

Codecs involved in the test:

  • CamStudio - CamStudio Lossless Codec v1.4 (LZO mode)
  • DivX - famous MPEG4 implementation, DivX v6.8.2. For most files (except gep) maximum possible in single pass compression was selected. In case of gep file bitrate was set to the same value as ScreenPressor, but picture quality was very bad whereas ScreenPressor kept it lossless.
  • Fox Magic - FM Screen Capture Codec v 1.00 (maximum compression mode for screen capture)
  • inno - inno Screen Capture Codec v1.20 (maximum compression mode), also known as WinCAM Video Codec
  • MSU SC - MSU Screen Capture Lossless Codec v1.2
  • ScreenPressor - our codec
  • TechSmith - TechSmith Screen Capture Codec v2.0.6 (maximum compression mode)
All codecs worked with the same key frame interval of 200 frames.

Files used in comparison:

  • browsing.avi - 932x720, 24bpp, 820 frames (0:54), 2107 KB
    A web browser scrolling couple of sites with text and graphics.

  • excel.avi - 1016x765, 24bpp, 3000 frames (5:00), 1683 KB
    Working on an Excel spreadsheet with added annotations.

  • gep.avi - 1016x845, 24bpp, 2281 frames (2:32), 7537 KB
    Using GraphEditPlus to build a youtube-to-avi converter in 2 minutes.

  • printer.avi - 800x600, 16bpp, 1256 frames (2:05), 237 KB
    Setting up a new printer in Windows 98.
As you may see, on a typical screen capture ScreenPressor shows the best quality of lossless compression. While lossy compression is known to be flexible in terms of bitrate, it has lower bounds, which in many cases for screen capture are very high compared to lossless codecs. In such cases lossless ScreenPressor provides not only higher quality but also better compression than lossy methods like MPEG4.

Compression speed

The seven codecs mentioned above were also tested for speed. Each codec decompressed video in its own format and then compressed it back. The task was performed in VirtualDub on a typical video (gep.avi). Next chart shows recompression speed in frames per second on an Intel Core 2 Quad (Q8200) @ 2.33 GHz. Since it includes both compression and decompression, the speed of compression only is approx. twice higher.

recompression speed

This test shows ScreenPressor to be one of the fastest screen capture codecs.

Optional lossy modes

By default ScreenPressor is lossless, however it also includes some lossy modes. One can adjust quality via settings dialog or via host application.

Different quality modes specify how many bits are to be thrown away from each color channel. Quality parameter varies from 100% to 50% meaning throwing away 0 to 4 bits from each byte. Here is an example of the same video frame compressed with 0 to 3 bits of losses:

As you can see these losses are hard to notice. However they can decrease file size dramatically:

Applying some losses decreases entropy in video and makes compression not only stronger but also faster, and decompression becomes faster as well.

Licensing

  • For end users:
    Decompression is free and limitless, anyone can download the codec and play files created with it free of charge.

    By default the ScreenPressor codec works as unregistered version. In this mode it will add a watermark to video when compressing more than 3000 frames or longer than 30 seconds. This allows you to test the codec and see if it fits your needs. Decompression is fully functional in unregistered version and has no limitations. If you only need ScreenPressor to play video compressed with it, you may do so free of charge and don't need to register. However, if you want to compress video without adding a watermark, you must register by purchasing a license. After purchase you'll get your personal registration code which must be entered in the codec to switch to registered version which doesn't add a watermark.

  • For developers:
    If you want to use the codec in your product or service such as screen recorder, VNC-like remote access application or platforms for online collaboration and web conferencing, you may license ScreenPressor and enjoy its compression power and speed. The codec is available as Windows VfW codec (32 and 64 bits), DirectShow filter, dynamic (DLL) or static library (both 32 and 64 bits) for Windows, Mac OSX and Linux, or source code for all these platforms. Please contact us for details.

History

Before ScreenPressor, world leadership in screen captured video compression was held by MSU Screen Capture Lossless Codec. Now it's obsolete and not supported anymore. The MSU codec's author Dmitry Popov, founder of Infognition Co. Ltd. (previously known as Dee Mon), is also the author of ScreenPressor.

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