Introduction

VirtualDub is a video editing tool which allows the user to perform basic editing tasks such as cropping frames, cropping video shots, adding video segments, adjusting audio tracks, and resizing video. Furthermore, VirtualDub has real-time video capture built-in so with a sufficiently fast CPU, one could capture DivX video in one step.

It also lets the user perform more general video filtering operations such as 2:1 reduction, 3x3 averaging, blurring, deinterlacing, embossing, sharpening, smoothing, and rotation.

VirtualDub separates the video stream from the audio stream so that the user can work on one stream without distorting the other. For example, if a video stream was encoded with mpeg-1 and pcm audio, then the user could read in the video using VirtualDub, leave the mpeg-1 video exactly as it is and just convert the pcm audio to mpeg layer 3 audio; or he could compress the video to DivX but leave the pcm audio as is.

VirtualDub does not read in vob/vts files directly. You would use a program such as Xmpeg for that process. However, Xmpeg does not read in DivX avi files. VirtualDub does read in DivX avi files. So, if you wanted to make an archival copy of your personal DVD, then you would use a program such as SmartRipper to decode the vob/vts files from the original DVD to your hard drive. Xmpeg could be used to convert the vob/vts files to a DivX avi file. VirtualDub could be used to edit the DivX avi file.

Resizing Video

Suppose you want to resize a video from 720x480 to 352x192, then you would (1) open the avi file; Two windows are shown which show the input video (left) and the output video (right). (2) Under the Video menu, select "Full Processing mode." Select Filters. Click on the Add button, click on the resize filter, and click OK. Type in the new resolution of 352 and 192 and select bicubic for the filter mode. Click OK to the dialog boxes. (3) Under the File menu, click on Save as Avi, type in a filename, and click on the Save button. You should see a window open which describes the processing of the video including how long it should take to process.

Joining Two AVIs

Suppose you want to join two avi files (vid1.avi and vid2.avi) together. To have the best chance of audio/video sync on playback you should add an end offset to the first avi file. (1) Load the movie (vid1.avi). Set both audio and video to "Direct Stream Copy." Click on Video | Select Range. Enter a small value (i.e. 15) in "End Offset" row in the Frames column. Save the movie as vid1a.avi. Now load vid1a and under File | Append Video Segment, load vid2.avi. Save the avi and hopefully the audio/video are in sync. Note that some audio codecs have a slight accumulating error in them such as the original mp3 codec which can result in out of sync audio/video

If the audio was compressed using a VBR (variable bitrate) method, then you might need to save the audio track as uncompressed before doing the resizing. To do this, select under the Audio menu, "Full Processing mode"; then click on "Compression" and select "No compression (PCM)." Click OK. Under the File menu, click on "Save WAV" which will prompt you for a filename. One hour of audio will be roughly 600 MB. When resizing the video, you should select from the Audio menu, "WAV audio" which will prompt you for an input audio file.

Re-Syncing Audio to Video

In some cases, you will have a video where the audio and video are out of sync. If you can determine the delay in the audio, then you can resync them by the following: Set both video and audio to "Direct Stream Copy." Select Audio | Interleaving. Suppose that the audio should be delayed by 800ms, then just put in the 800ms in the delay box. Save as Avi. For an hour long video, this process should take only 2 minutes.

Processing an Entire Directory

Another powerful feature of VirtualDub is the ability to process all the video files in a directory. First, set the audio and video compression to your preferences. Second, go to File | Job Control. Select Edit | Process Directory. A dialog box will appear which prompts you for the source directory and then the destination directory. Afterwards, just click on the "Start" button in the VirtualDub Job Control box.

Using DivX 2 Pass Encoding

Load your AVI. In the video compression configuration of DivX, select 2 pass, 1st pass and select a bitrate. Go to the Save Avi As dialog box and click on "Add operation to job list" box. Enter a filename such as "myvideo-1stpass" and click Save. Now, go back into the video compression configuration of DivX and select 2 pass, 2nd pass. Don't change the bitrate from the 1st pass. Go to the Save Avi As dialog box and click again on "Add operation to job list" box. Enter a filename such as "myvideo-2ndpass" and click Save. Now click on File | Job control and click on the Start button. VirtualDub will place the final avi in the 2nd pass filename which in our example was "myvideo-2ndpass."