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.
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):
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).Codec
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”
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.
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, version 2
- 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 – 932×720, 24bpp, 820 frames (0:54), 2107 KB
A web browser scrolling couple of sites with text and graphics.
- excel.avi – 1016×765, 24bpp, 3000 frames (5:00), 1683 KB
Working on an Excel spreadsheet with added annotations.
- gep.avi – 1016×845, 24bpp, 2281 frames (2:32), 7537 KB
Using GraphEditPlus to build a youtube-to-avi converter in 2 minutes.
- printer.avi – 800×600, 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 of version 2
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.
This test shows ScreenPressor 2 to be one of the fastest screen capture codecs.
Speed of version 3
In 2017 we changed the entropy coder and improved parallelism in compression code, this way version 3 was born which is significantly faster, although the compressed files end up a few percent larger than with v2.
On a Core i5 @ 2.4 GHz the video gep.avi from the comparison above (2281 frames, 1016×845 pixels each) shows following recompression (decompress + compress) speed:
Version 2: 11 seconds recompression time, ~207 frames per second.
Version 3: 7 seconds recompression time, ~325 frames per second.
Another sample with typical screen content (some office work, some browsing scrolling images and youtube page, some windows with text moving) vid_sp3.avi (6 MB) – 675 frames of 1364×768 pixels, shows following recompression (decode+encode) speed on same Core i5, in frames per second:
|Version 2||79 FPS||52 FPS|
|Version 3||162 FPS||176 FPS|
Encoding and decoding times are similar, so for purely encoding or purely decoding speed multiply these numbers by 2.
Effectively, in this test ScreenPressor 3 shows 300x lossless compression at 300+ frames per second.
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.