Digital Imaging -Tech Talk: DIGITAL STREAMING VIDEO

Our Erlangshen family of cameras (ES500W, ES1000W) , offers a standard and unique feature called digital streaming video output (DSV). This video format is in comparison to the older TV standard of analog video format. It is also available as an option on any of the other Gatan CCD cameras. DSV is a plug-in to Digital Micrograph software.

The streaming video produced by the plug-in can be viewed or captured by any software application that supports this type of video signal, such as Microsoft NetMeeting, or other commercial software. It is the goal of this document to summarize what we offer and the capabilities via 3rd party software.

1. Introduction

Digital streaming video (DSV) is widely used in webcast (webcam) applications. It is generated by computer software that controls a digital camera. Compared to an analog video signal, a DSV signal can represent a “gain normalized” image. Since Digital Micrograph controls the acquisition, any processing done to the image can be transferred to the DVCapture module as the DSV stream. This means the resulting stream is essentially free from detector cosmetic imperfections or gain variations. DSV therefore has a much higher video quality than analog video.

2. Principle of Operation

The digital video stream as it is delivered by the DVCapture module within DM is intended to be used by another software program. Digital Micrograph acts as the supplier of the digital stream. Additional software is needed to “use” the DSV output. Within the DM user interface a separate menu item called DVCapture will be seen. You can use this menu to access Setup, Start and Stop of the video stream. The “Window” pull-down menu in DM will also allow you to show the floating window called Digital Streaming Video (Fig. 1).

This window allows you to quickly make changes to the video size of the stream being sent. This same information can be accessed via Setup (Fig. 2)

The “Video Size” selection has numerous choices to pick from. Your selection should best match the aspect ratio of the camera as well as the final size you want sent out to the digital stream. The current upper limit for size selection is 720 x 480.
The “Image Window” and “Image Capture” settings seen in Fig. 1 and 2 respectively should be set to “Front Image”. This simply tells the software that you are using the current active or “front” window in Digital Micrograph. You can also stream any static, saved image by opening it into Digital Micrograph and making sure it is the “front image”.

If you have created any annotation on the image, such as a micron bar, and want it to be included in the video stream, make sure you check the box labeled “Capture Annotations” shown in Fig. 1. This can also be selected in Fig. 2 in the box labeled “Include Annotations”. Be aware that including annotations into the video stream can affect (slow) the final frame rate. Since we are not dealing with color images from the camera, also make sure you check the box labeled “Capture in BW” shown in Fig. 2. The interval time (ms) shown in Fig. 2 refers to the amount of idle time between digital frames. The value you should use should be set to 60 ms. This value will be satisfactory for even some of the cameras that have slower frame rates.

After making your selections for the video stream, clicking on the “Start Video” button will send any live image currently being acquired by the camera out as a digital stream. To get the fastest frame rate for the camera, make sure the correct exposure time and binning are selected for the camera being used. Refer to Table 1 and Figure 3 for settings used in DM for the Camera View window/setup for the appropriate camera. The user can now toggle over to the appropriate 3rd party program on the PC to use the video stream or create a movie for saving.

Depending on what the intended application need is, the additional software needed can range from simple “shareware” programs to commercially available video authoring programs. An easy example of free software that can use this streaming video is Microsoft’s NetMeeting. The “live” image can be displayed in NetMeeting and shared with others over an internet/Lan connection using this type of program. The drawback with NetMeeting is that it cannot save a session into a movie file format, and the displayed video size is limited by NetMeeting.

If the application need is to create actual movie files that can be played back, saved to CD/DVD, used on a website, then a commercial program should be utilized such as ULead System’s VideoStudio 9.0. Using a program such as this, the digital stream from DM is recognized as a capture device (DMVideo) to which the VideoStudio program can then capture and create a video movie in a variety of formats (avi, wmv, mpeg). There are also many editing, special effects, composing features, audio track input, etc. that are part of this program. VideoStudio 9.0 has been tested and shown to be compatible with Gatan DSV output.

The user should also pay attention to the format size that the movie creation program uses for video input. As mentioned earlier, you should try to match what format was selected in the DSV menu to the capture format used by the movie creation software. Some movie creation programs use additional processing when creating the movie if the source size is not matched properly to the output size of the final movie. This could have an affect on the overall frame rate and appearance quality of your movie.

3. Application Uses

DSV is the ideal choice for in-situ TEM observations. Other examples of use are: movies teaching new users the use of a TEM; live session views showing low mag/high mag surveying; dynamic real-time experiments showing changes in a sample when using heating/cooling holders; sharing of large sets of data images via a movie instead of individual image files; conference call sharing using NetMeeting (allows the researcher to collaborate with remote sites in seeing the video stream live as it is being acquired). There are probably many more that you can think of but the point illustrated here is that DSV gives the end user a powerful tool that can help in productivity and promote data results quickly.

4. Availability and Requirements

DSV is a standard feature in GMS 1.4.3 and higher, for the Erlangshen family of cameras (ES500W and ES1000W) and optional to other Gatan CCD cameras, including GIF CCD cameras.

The minimum suggested PC hardware requirements are:
• Pentium 4, 2.0 GHz CPU or higher
• 512MB of RAM
• 7200 rpm IDE hard drive (80GB)
• 1.2GB or more of available hard drive space for program installation
• Windows-compatible display with at least 1024x768 resolution
• Microsoft® Windows® XP
• SP 1 (SP2 also compatible if GMS 1.4.3 is installed)

If you will be using the full features of a video authoring program like VideoStudio 9.0 then you will benefit greatly by having additional RAM memory (1GB or higher), a CDRW or DVD-R+R drive and at least 20GB of available hard drive space for burning to CD/DVD.

Ulead® is a registered trademark and Ulead VideoStudio™ is a trademark of Ulead Systems, Inc. Some of the product names used in this document are trademarks or registered trademarks of their respective holders and are used for identification purposes only.

Microsoft, MS-DOS, MS, NetMeeting, Windows, Windows NT, DirectSound are either registered trademarks or trademarks of Microsoft Corporation in the U.S.A. and/or other countries.

For technical and ordering information on Gatan imaging systems and software, please contact your local Sales office.