How to Convert WMA to MPEG4

It's Time You Learned

While you can edit the proprietary WMV video file format, it may be difficult to find a useful tool with the abilities you want. On the other hand, editors for the MPEG-4 format, such as Avidemux, Pinnacle Studio, Quicktime Pro, or Adobe Premiere have many features. Use the free, open-source tools VirtualDub and AviSynth to convert WMV to MPEG-4.

Things You'll Need

• VirtualDub - free video processing software (1.8.5 Portable used here)
• AviSynth (when using VirtualDub to load non-".avi" movies)
• High-quality video codec - either XviD or x264 (both free)
• LAME mp3 audio codec

Instructions

All Editing Requires (Re)Compression

1. Use AviSynth to load our non-AVI video in VirtualDub. Create a text file with the extension ".avs", open the file in Notepad, then enter the text: DirectShowSource("<FILEPATH>"), replacing <FILEPATH> with the complete directory path and filename of your video. For example, "D:\Video Samples\Snow Sliding.wmv."

2. Load the .avs file in VirtualDub from "File / Load" or drag-and-drop (shortcut: CTRL+O). Go to "Video" and select "Full Processing Mode." "Compression" is now available under "Video" -- select it, and in the popup choose "XviD MPEG-4 Codec."

3. 

   Press the "Configure" button to select the specific settings. These settings will affect the video quality and file size, but for a typical digital camera the following settings should be fine:
   - Profile @ Level: Advanced Simple @ L5
   - Encoding: Single Pass
   - Target Quantizer: around 8.00 to 12.00 (lower number means higher quality and larger size)
   - Other Options (button) - Profile (tab) - Quantization Type: H.263

4. Run the processing by going to "File / Save as AVI" or press the shortcut key "F7."

5. 

   If you have multiple videos to process, when saving check the box at the bottom-left of the Save window that states "Don't run this job now; add it to job control..." Do this for each video, and after saving the last video go to "File / Job Control" (shortcut: F4), then click "Start" to begin processing.

Choosing the Right Compression

1. 

   Match the source video properties as closely as possible to get the best results. View these properties from "File / File Information." Pay particular attention to the "Data rate", given in kbps.

2. 

   Go to "Audio / Full Processing Mode." Then select the "Compression."

3. Choose "LAME MP3" and try to match the original source's Sampling rate (usually 44100 Hz) with a bitrate of at least 96 kbps. Some cameras record with uncompressed sound, and so file sizes can be significantly reduced by encoding the soundtrack as an MP3.

Tips & Warnings

• Different codecs provide different quality/filesize ratios; some may also not be immediately compatible with other systems. Both XviD and x264 are types of MPEG-4 compression, with different strengths and weaknesses - XviD is fast and is lighter on the processor, but x264 can retain better quality for the same size. Experiment with the compression settings. What may work well for video from one camera may not work when converting a movie downloaded from the internet. Try to find some common settings and reuse the compression "profiles" by saving and loading the processing settings from the "File" menu (shortcut: CTRL+S and CTRL+L). To use x264 compression, install and use "x264vfw - H.264/MPEG-4 AVC Codec" configured as: - Main: Single pass - ratefactor-based (CRF) - Ratefactor: around 20.0 to 25 (lower number means higher quality and larger size) To use x264 compression, install and use "x264vfw - H.264/MPEG-4 AVC Codec" configured as: - Main: Single pass - ratefactor-based (CRF) - Ratefactor: around 20.0 to 25 (lower number means higher quality and larger size)

• Making any change to a video, especially switching the codec used to view it, unfortunately requires that you recompress the video. While compression has the benefit of reducing the file size, it can also affect the video quality. With VirtualDub, you have several options for compression, and many settings for quality and file size, depending on the codecs installed on your computer. The output will have the extension "avi", since it is a type of audio/video container, but the video will be encoded with a type of MPEG-4 codec. Not all computers may have each codec. If someone complains that your video is blank, or doesn't play, they may need to download the appropriate decoder. Increasing the quality of the compression may also increase the time it takes to encode the video, especially for less powerful processors. If the audio doesn't match the video of your converted file, you must specify the video framerate and convert it in the .avs file, for example: DirectShowSource("<FILEPATH>.wmv", FPS=25, ConvertFPS=True). Check the "File Information" to find the video framerate.

References

• Audio/Video Sync with WMV in VirtualDub
• A more in-depth explanation of XviD encoder settings
• A more in-depth explanation of x264 encoder settings

Resources

• XviD codec - information and download
• x264 codec - Video for Windows version