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| 1. Why do we support the AVI files with the uncompressed video stream only? First of all, in most of the cases, the output video files from video cameras can be saved as AVI files, and that is the reason why we choose AVI files. Second, referring to the format of the AVI files, the video stream can be compressed with different compressed algorithms. But one should decompress the video stream by the corresponding algorithm. Uder Windows, with vfw32.dll we can easily use VCM(Video Compression Manager) to locate the needed coding/decoding program and use it to decode and code video data. However it's not so convenient under Linux. It's hard for us to implement the complete version in such a short time. Finally we only support those AVI files with uncompressed video streams only .

Luckily there're numerous converters which can convert other format of video files to an uncompressed AVI file, such as¡®the Boilsoft ASF Converter'.

In a word, it's a try to provide video processing functions for Scilab, the version that we have offered is excellent for temporal scientific experiments. But more support will be expected in the future.

2. Why is the processing so slowly sometimes?

Well, both the image and video processing are supposed to be fast under Scilab, but unfortunately it seems not. The mainly reason is that the image data stored in Scilab is not consistent to the prevalent storage type. SIP makes a conversion of the original image data and passes it into Scilab. The conversion makes a M ¡Á N ¡Á 3 array to be a 3 ¡Á N ¡Á M array in the description of C language. However, before the processing performs, the array should also be converted to the original one, for the need of the mature algorithms. Those conversions and reversed conversions are quite a time waste! But it's needed for displaying the images in the current Scilab version - the red, green and blue vectors are separated. And SIP does those conversions. Furthermore, V.I.P.Scilab has to follow those conversions for using the image processing functions in SIP. So if one would like to accelerate the processing speed, then the type of the image data passed to Scilab should be changed.

3. Sometimes when you display a truecolor image, but the result may be an all-white area or an all-black one or an image that is not the one you want.

The possible cause is that elements of the parameter of the function imshow are too large or too small. Here the parameter of the function imshow is an image matrix that is going to be displayed. Now adjusting the elements of the image matrix to proper extent may be OK, such as multipling 256, dividing 256 and so on. Under Windows, elements of the image matrix shoule be between 0 to 256 for normal display, while under Linux, 0 to 1 is required.

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