For video rendering choosing the right video codec (compressor / decompressor) is a decisive factor. It reduces the data volume to a tolerable amount, but also increases the rendering period and reduces the quality compared to the original picture. This can become a vicious circle, where compromise is the only way out!
Wings Vioso RX comes with virtually all codecs. For superior video quality we recommend the H.264 codec. For high compatibility with Windows computers we recommend the WMV codec by Microsoft which is based on MPEG 4 and allows good quality even at a lower data rate. See also MPEG-2, H.264, H.265 or WMV format?
A larger picture requires longer rendering time and, consequently, produces a higher data rate. Moreover, playback requires increased computer capacity and a data source which maintains a constant data rate. The latter is particularly important for Internet applications. For most codecs, e.g. DivX and Intel Indeo 5.10 and WMV, pixels for height and width must be dividable by 4. This means that a picture with a resolution of 750 x 500 pixels would not be admissible, but only one with a resolution of 752 x 500 pixels. The larger the image the higher is the required playback performance. As you will realize when you go on to the other paragraphs below other factors also have an impact on the playback performance.
The frame rate has a direct effect on rendering duration, data rate and computing speed required for playback. Too low a frame rate results in jerky dissolves or movements. For a dissolve show with still images 20 to 30 frames/second would be a good solution. For shows containing screen field movements, panning or zoom movements via high-resolution still images, you should choose a minimum of 30 frames per second or possibly 60 frames/s for fast movements - modern WMV codecs and fast computers easily come up to this task. When videos are to be integrated, too, it is a good idea to choose the original or double the original frame rate, i.e. 25 or 50 frames/s for integrated PAL videos. See also Media integration.
A video, just like a film, consists of a number of consecutive pictures. When a video is compressed, for some pictures only the keyframes (also called I-frames) are saved instead of the complete pictures. For all the other pictures, the codec only saves the differences compared to the previous picture, which has a favorable effect on the data rate. When there are longer intervals between the keyframes, the video is difficult to scroll and you may have problems starting it from any possible location. The default setting of the DivX or WMV codec saves one keyframe for every 300 pictures, which corresponds to an interval of 12 seconds at 25 frames/second. This has an unfavorable effect on scrolling, but allows a low data rate. In DV or Apple ProRes 422 HQ videos, on the other hand, each picture is one frame, i.e. it virtually consists of keyframes only. For MPEG-2, the keyframe interval is usually 15 frames and for H.264 up to 300 frames.
As explained above, the data rate depends on a variety of factors. Another one of these factors is the compression quality, which can be adjusted for some codecs. Avoid high values as the improvements in quality will no longer be visible and rendering will take unnecessarily long. Other codecs feature a data rate adjustment, which in turn has an influence on the compression when picture size and frame rate are predefined. The data rate actually produced also depends on the show (type of media, number and type of dissolves, etc.) and can not be specified exactly in advance.
This is particularly true for video rendering. Usually, presets are a good basis for your own experiments. Start with shorter videos and smaller picture sizes and try out various settings until you have found the optimum solution. Choosing too large a picture size to start with will cause jerky playback and you may not be able to find out what parameter settings cause this. You may also have to consider that somebody else's playback computer may not be as powerful as your own computer. Do not push your computer to its limits. You may need some "spare capacity" during a presentation to avoid jerky display and intermittent sound and this might wreck your show.
For problem analyses Wings Vioso RX offers a performance test for individual videos or for a complete timeline. See also Performance test for videos and Performance test for complete timelines. By the way: Windows also features a task manager which provides information on the system resources (open by right-clicking the task bar). It will tell you about the available resources of your computer during playback. The main processor is responsible for decoding. What is also important is the performance of the graphics card and the memory throughput. Tab "System Resources", however, does not provide sufficient information on this. Notebooks in particular may have distinct weaknesses in that respect ... See also Optimizing the presentation PC.
Well, have fun Producing your video!