Requirements for Playing Videos in DIAdem VIEW

To be able to play a video you must install the codec with which the video file was coded. Additionally, the software used for video playback must support the format of the video file. Codecs Codecs are used for coding and decoding video signals. The coding, or encoding, usually includes a compression for reducing the data rate required for the transmission. The storage space required for storage in a file also decreases greatly. For the video playback the encoded video signals must be decoded with the same codec. Codecs with a higher compression rate usually require more computing power when encoding and playing videos. Earlier codecs use a process similar to the JPEG compression to compress each frame in the video separately from the other frames. Newer methods additionally consider the fact that the differences between successive frames are very small. This method is called interframe compression and combines key frames and delta frames in order to increase the compression of video files. Interframe compression is used especially for video streaming. Codecs without interframe compression, for example, the DV codec, are still important for video cutting and as an exchange format. In an interframe compression the key frame contains all information required to display this frame. The delta frame, however, requires data from other frames in order to display. All videos contain at least one key frame at the beginning. Additional key frames improve the continuity of the video but also increase the file size. The more key frames a video contains, the easier the positioning within the video is during playback. The encoded video signals that a codec generates are saved in a file. Codecs do not always have the same name as the file format they create. Therefore it is important to differentiate between codecs on the one hand and file formats or container formats on the other hand. You can save various video and audio tracks that were encoded with different codecs in one container format such as AVI. Container Formats In software technology, a file format that can contain different file formats is called a container. A container format only defines the type and structure of how to save the contents. Containers facilitate, for example, the storage of audio and video tracks in one file. Often the container formats AVI, MPEG-1, MPEG-2, or MPEG-4, are used for videos. AVI (Audio Video Interleaved) is a container format for videos defined by Microsoft and derived from the RIFF (Resource Interchange File Format) that was introduced for Windows 3.1. An AVI file can combine contents such as bitmaps, audio and video files, or RTF texts that were encoded with different methods. The content type is saved with a Four Character Code (FourCC). This four character long string in the header of the AVI file specifies which codec to use for decoding the data. Videos in DIAdem Since version 10 DIAdem VIEW can play videos. When playing videos in DIAdem VIEW, the main focus is on the synchronization of measurement data and video signals. To synchronize the time information of the various data sources, DIAdem must position the video to certain time points. This is the only way to synchronize the video display when you scroll with the cursor through the measurement data. Positioning the video is always easier when the codec

National Instruments, NI, ni.com, LabVIEW, and DIAdem are trademarks of National Instruments Corporation. Refer to the Terms of Use section on ni.com/legal for more information about National Instruments trademarks. Other product and company names mentioned herein are trademarks or trade names of their respective companies. For patents covering National Instruments products, refer to the appropriate location: Help»Patents in your software, the patents.txt file on your CD, or ni.com/patents.

© 2006 National Instruments Ireland Resources Limited. All rights reserved. does not use interframe compression. If you reduce the distance between the key frames in the settings of the codec with interframe compression, you can improve video playback in DIAdem VIEW. The video wobbles less during playback and the wobbling starts later within the video. Codecs Tested with DIAdem Refer to the National Instruments KnowledgeBase under the search term DIAdem Codecs for a current list of codecs1 tested with DIAdem.

Table 1. Preliminary List of Tested Codecs (from June 2006)

Codec Name Origin Restriction / Comment

1 Intel Video 3.20 Win XP SP2

2 Intel Video YUV (uncompressed) Win XP SP2

3 Microsoft Video 1 Win XP SP2

4 Cinepak Codec by Radius Win XP SP2

5 DV-Codec Win XP SP2, Windows This DV-AVI format corresponds with standard DV camcorders. Movie Maker 2

6 DivX 6.2.2 www.divx.com (1), Generates the smallest files.

7 WMV9 MS Encoder Pack (2), With this codec you can save WMV9 compressed videos in AVI containers.

8 MS Mpeg4 V1 MS Encoder Pack (2)

9 MS Mpeg4 V2 MS Encoder Pack (2)

Restriction 1: If the playback speed is unequal 1 at an unchanged frame rate, the video might wobble. The wobbling increases as the video proceeds. For example, the wobbling can start after 10 seconds, can increase after 20 seconds, and the display can stop after 40 seconds. Restriction 2: The same as restriction 1. However, the video wobbles less if the playback speed range is between 0.5 and 2.0.

DIAdem Cannot Play a Video Error message: "Cannot load video file" If you cannot play a video in DIAdem, it is usually sufficient to open the video in the Windows Media Player. To install the required codec you activate Download codecs automatically in the menu Tools»Options»Player.

If the Windows Media Player does not install the missing codec, you can use a special software, such as the free of charge GSpot (www.headbands.com/gspot) to read which codec you need to play your video file. A quick internet search usually provides the required codec. With the GSpot software you also can check which codecs are installed on the computer and which codec belongs to which Four Character Code (FourCC).

Error message: "Codec does not support precise synchronization" DIAdem cannot play the video, because the information required for the positioning is missing. Encode the video file with a different codec.

1. To test the codecs the example video glass.avi supplied with DIAdem was encoded with the software VirtualDup 1.6.11 using the specified codecs, and then played in DIAdem VIEW.

Videos in DIAdem VIEW 2 ni.com