Comparing Video Formats

Buy an original DVD from the market, pay a good amount of money for it and then one fine day you end up scratching it. This makes it imperative to back up your DVD's in your PC, so you can watch them at your convenience.

Taking backup brings up the issue of the tremendous amount of space that DVD format movies tend to take. And it is not possible to spare 3 or 4 GB of space for every DVD that you want to back up. This makes it necessary to back up your movies in the proper format, so that they do not occupy all that space, and also not compromise on the quality of the movie.

There are compression formats specifically devised for this purpose. Moreover, these days DVD players come with built in capability to play a number of compressed video formats such as DivX and MPEG-4. Since this feature was not there earlier so it was not favorable to store compressed video in a DVD or CD, but now DVD players such as the Philips DVD320 offer playing compressed video as well.

There are various video formats such as MPEG-2, MPEG-4, DivX and WMV (Windows Media Video), that offer a combination of compression, resolution and frame rate settings, which allow video to be delivered according to your needs and the PC's requirement. Now the problem is that each format claims that they can deliver maximum amount of compression, maintaining the same level of quality. So, we decided to test some of these compression formats and see what they can

actually do.

Comparing the formats



We used a utility known as FlaskMPEG to convert the video into various formats. FlaskMPEG can be downloaded from www.flaskmpeg.net. Here's how you can convert your DVD format video into other formats. 

• The first step of course is to rip the DVD and store it on the PC. Ripping the DVD and copying the files will give a bunch of files in VBO format to your hard disk.
• Open FlaskMpeg and then open the file whose format you want to convert by clicking on the File menu and then on 'Open Media'. In the new window select the video to be converted.
• Now you will get another window, here click on 'Select Output'. Then you need to choose the codec, using which you would encode the video. Choose DivX for maximum compression and good quality.
• In the same 'Select Output' window, click on 'Audio Codec', where you need to select the desired video output. Select 'MPEG layer 3' for best results.
• Once you are through with selecting the codes, all you need to do is click on the 'Flask It' button in the main window to start the encoding.

You can specify the audio and video quality, while converting a file into WMV format using WME

The video can also be converted into other formats such as MPEG-3 or MPEG-4, which is again a very high compression format. The other option is to convert the video into WMV format. This can be accomplished using a tool, WME (Windows Media Encoder), which can be downloaded from www.download.microsoft.com. Here's how you can create WMV file.

• After opening WME, click on the File menu and then on 'New' in the resulting drop-down menu. WME will then prompt you to select the kind of task to be performed. Here, click on 'Convert a File' and then click on OK.
• In the resulting window specify the location of the file to be converted, and the location at which the new file is to be placed. Once this is done click on Next.
• Now you will be prompted to specify the way in which you intend to stream the file (as WME is widely used for steaming of videos). Select 'Computer Playback (file download)' and then click on Next.
• In the resulting window, specify the desired audio and video quality ie DVD quality with 2 Mbps at VBR (Variable Bit Rate) or very high quality video at 5 Mbps for video quality, and there are many other options as well. Once through with this, click on Next.
• Now just specify the title and other details about the video, and click on Finish to start the conversion of file.

FlaskMPEG will support conversion to most of the formats provided you have the requisite Codecs

For compression, we converted a single title of a DVD movie in to MPEG-1 sized 68 MB and then this file was converted into DivX, MPEG-4 and WMV. In our test, DivX took lesser time to encode compared to others format mentioned above. As far as size is concerned, MPEG-4 scored least in size marginally scoring over DivX, followed by WMV. MPEG-4 came out to be 43.9 MB, DivX was 52.7 MB and WMV was 44.0 MB

There are other tools available that can be used to convert videos from one format to another. Some of the ones that we used were MovieDB, Virtual Dub and

htencoder.

Ankit Kawatra and Sanjay Majumder

Compression formats explained

MPEG-4: This is a standard for multimedia and Web compression. In this kind of compression, individual objects within a scene are tracked separately and compressed together to create an MPEG-4 file. This results in very efficient compression that can vary from low-bit rates to very high-bit rates. It also allows developers to control objects independently in a scene.

MPEG-7: This standard, currently under development, is also called 'Multimedia Content Description Interface'. It is aimed at providing a compression format for multimedia content that will include information on content manipulation, filtering and personalization, as well as the integrity and security of the content. This means that contrary to the previous MPEG standards, which described actual content, MPEG-7 will represent information about the content.

DivX: It is a software application that uses the MPEG-4 standard to compress digital video and maintain its quality. You can download nimo, which will install the latest codecs on your machine including

DivX.

If you are developing a video for the Internet, you may want to use a compression format, which has a high compression and low resolution, such as RealVideo, QuickTime or Windows Media Video.