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Thumbnail of the CryptoTE screencast

Experiences Producing a Screencast on Linux for CryptoTE

Posted on 2009-08-17 11:25 by Timo Bingmann at Permlink with 0 Comments. Tags: linux

While publishing screenshots for CryptoTE (nice cross-platform text editor with integrated cryptography) the idea of making a short tutorial screencast came up. A screencast is basically a video made directly from the computer screen with no camera involved. Usually speech comments are added to create a sort of impromptu screen presentation. Thus I could show off the cool features of CryptoTE, and people could see what the program is about without installing it.

So far the cool and very trendy idea, now for sorting out the technical difficulties in making such a video. In theory a screencast video should be well compressible with a lossless codec. Unresized screenshots in full-resolution are also better compressed using the lossless PNG format than with JPEG, the PNG files are much smaller and show no blurry edges. Similarly screencasts, being only a sequence of full-resolution, losslessly recorded screenshots with some little mouse-movement, should be compressed losslessly.

On the digital inspiration blog I found a detailed "Screencasting Software Guide - Review of Desktop Screen Recording Tools" for all platforms. However, because my primary operating system is Linux (and since I also wanted to show that in the screencast), the range of tools that actually work is very limited.

This blog entry continues on the next page ...

lcov: A Good HTML Generator for gcov Results

Posted on 2007-05-08 11:08 by Timo Bingmann at Permlink with 0 Comments. Tags: c++ linux

Writing test cases is a good way to prevent and detect problems or bugs in source code. They improve understanding of the difficult parts by requiring deeper thought into how to test of those areas. By rerunning the same test sequences one can assure that the code still produces the same results even after making significant changes. cppunit provides a C++ test framework which is sort of over-bloated. However reduced to a set of reusable template files the framework gets quite handy.

To measure how much of the code is tested, gcov provides a way to determine which lines are executed during a test suite run. Note that this simple line-is-touched metric is only one aspect of how well a piece of code is tested. However gcov's results are printed in text mode and it cannot merge the results from multiple coverage files, so multi-file test suites cannot be measured as a whole.

Yesterday I finally found a good open-source Linux tool to get correct coverage results: lcov. It was designed to measure coverage in the Linux kernel, but works very well on user-space programs as well. lcov builds on gcov's data files and generates HTML report files. It even highlights the untested source code lines.

I uploaded the test coverage results of the STX B+ Tree test suite. It shows 89.2% coverage of the main, most difficult header file implementing the insert and erase algorithms.


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