Video Processing

Now that the applications are installed and ready to use, we need to determine some information: the video resolution and frame rate.

Each video file has a width, height and frame rate - the number of pictures shown on the screen in one second. The resolution and frame rate of our video file can vary but, if we want to convert to Video CD, the video needs to have a specific resolution and frame rate.

If we start Tsunami MPEG Encoder, the first page of a wizard will ask you to choose the conversion format.

In this tutorial, I will encode the video to Video CD, PAL because I live in Europe and the standard for TV in Europe is PAL, with some small exceptions. This means the movie resolution will have to be in the end 352x288 (width x height) and the number of frames in one second will have to be 25.

If you live in the United States Of America or other countries outside Europe, the NTSC profile may be more suitable. It has another resolution, 352x240 and 29.97 frames in a second.

However, most modern portable players have no problems decoding both NTSC and PAL, no matter what country you're in.

Please write down or memorize the resolution and frame rate as we're going to need these later. Click on Cancel and then close Tsunami MPEG Encoder.

Now that we know what resolution and frame rate our video has to be converted to, we need to know the resolution and frame rate of our movie.

Start VirtualDub and use the "Open video file" option from the File menu to open your movie.

If VirtualDub shows a message box about the sound of the video having a variable bitrate audio stream, we will have to decompress the whole audio track and replace the original audio track in the movie with the decompressed audio track.

The variable bitrate is a special method of encoding the audio information in the movie and VirtualDub doesn't like it.

For the moment, just click Ok. Later in the tutorial we'll go through the steps required to fix the sound.

Once you see the video file in VirtualDub, select the "File Information" option from the File menu and you will see the following screen:

As you can see in the image, my video resolution is 480x276 and my video frame rate is 25. This means I will have to resize the video somehow to 352x288, the Video CD resolution defined in the standard, the PAL version. I won't have to change the number of frames per second because my movie already has 25 frames per second.

Go to the Video menu and select the "Full processing mode" option because we need to make changes to the video part of our movie.

The movie can be resized in VirtualDub using a filter called "Resize". Open the Filters window by selecting the "Filters" option in the Video menu. Then, click Add, select the "Resize" filter from the list and click Ok.

The filter's configuration panel will appear and you will be able to resize the video.

We can not resize directly to 352x288 because the video will be distorted, the aspect ratio will change. The new width and height must be proportional to the old values, that's why we'll use a simple rule:

If we know the original width and height and whish to resize the video to a new width, then the height equals is the division between the new width multiplied by the original height and the original width:

So, if my original width is 480 and my original height is 276, the new height will be :

which means that in order to preserve the aspect ratio of the video, the new resolution should be 352x202, because the values are rounded to the closest number.

From the combo box available right below the two text fields, we can choose the resize algorithm available, from the lowest quality to the highest. The "Lanczos3" or "Precise Bicubic (A=0.60)" are the best resizing algorithms available.

In order to reach the desired resolution - 352x288 - we have to add black bars on the top and bottom of the frame so we will check the option called "Expand frame and letterbox image"� and type in the two text fields the desired values, 352 and 288:

Click on "Show preview" if you wish to see how the video will look after the resize process or close the configuration panel and the Filters window, to see how the video looks in VirtualDub's window:

Now that our resolution is right, the next thing we need to take care of the frame rate. In my video, the frame rate is just right, I don't need to alter it.

If you do, select the "Frame Rate" option from the Video menu, click on the "Convert to fps:" radio button and then type the desired frame rate in the text box on the right:

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