Having purchased The Sunbury 30th Anniversary Rock Concert DVD I attempted to play the DVD on the computer. However, a message appeared in Windows Media Player notifying that codecs need to be downloaded to play the DVD. How do I find these codecs? I have tried updating Windows Media Player from version 10 to version 11 but this has not helped. Also, another message appears saying the DVD is locked and encrypted, and this must be played in a DVD player first. Can you explain this message?

After researching this DVD on the internet I was unable to find any references to problems with playback on computers, using Windows Media Player, particularly those requiring particular codecs to be installed for the DVD to correctly play. In case you are not aware, codec is the abbreviation for compression/decompression. Video and audio traditionally carries a lot of data, and uncompressed video can be as large as several tens or hundreds of gigabytes. Obviously this is not useful for mass distribution of movies, as there is no feasible or affordable storage media to hold such a large amount of data. So, codecs are used to compress the data into a smaller format so that it can be distributed. This means that a movie which may be very large in the raw uncompressed format can be compressed onto a 4.6 GB DVD disc. Obviously such compression does decrease the quality of the picture and/or audio under compression. This is called lossy compression, as parts of the video or audio are “lost” during compression. Usually those parts which are lost are deemed to be non-critical parts which do not affect the overall quality of the production, and therefore are acceptable to lose. However, when you compress a media the device which plays back the media needs to have the appropriate decompressor so it can understand and interpret the compressed data. This is analogous to ZIP files on computers. You can compress a lot of data within ZIP files, and then send this ZIP file to others, but if the receiving party does not have a program capable of opening and decompressing ZIP files obviously the data within the ZIP file cannot be accessed. In this case, it seems the DVD was compressed with a particular compression scheme not found on your system, and thus your computer cannot play back the DVD.

The only obvious cause of such an issue, without having the DVD itself to experiment with, is that the DVD has been mastered in a PAL format. This is the video playback format used in Australia, rather than the NTSC format used in the United States. It is possible that Windows Media Player is having difficulty playing the PAL format and is requesting additional codecs to be installed to assist the playback. However, I have never encountered problems with the video format (PAL or NTSC) before so I doubt whether this is the true cause of the problem. Unfortunately Windows Media Player is often quite economical with the amount of information provided regarding codec problems, and generally does not present any information about the codec which needs to be installed.

One way to work around the problem is to use a different program to play the DVD. An excellent program is VLC Media Player (www.videolan.org). This is a superb, open source media player which has most codecs built-in and will play almost any video file. Once you have and installed VLC, open the program then go to the “File” menu > “Open Disc”. In the window that appears the default option should be alright, so click OK and the DVD disc will attempt to play in VLC. All being well, you should be able to play the DVD through VLC Media Player.

However, if you still wish to play the DVD through Windows Media Player you may have to go through a rather complicated process to determine the codecs which you need to install. A good utility which can determine the required codecs for a video file is called GSpot (www.headbands.com/gspot). This is a free utility which allows the user to specify a video file, and GSpot will provide information on the codecs used in the video and whether these are installed on the computer. For a DVD, you will need to point GSpot at the relevant VOB file(s) on the DVD. VOB files are the files on the DVD which actually contain the video and audio. Most DVDs have multiple VOB files, so it can be difficult to determine which VOB file(s) contain the main (feature) video. However, you can generally assume that the largest VOB file(s) contains the feature video, and these are generally substantially larger than the other VOB files (normally several hundred megabytes larger). Be aware, when reading documentation relating to GSpot it has been commented there is not full support for VOB files, given the complexity of this file format. Therefore, GSpot may not provide full information regarding the VOB files. That said, it does at least provide a starting point.

Regarding the second error message that appears, pertaining to the DVD being locked and encrypted, this message is likely being caused due to Windows Media Player being unable to play the DVD due to missing codec files, and is probably nothing to worry about in itself.