Convert WMA to MP4

A format of audio stream coding deployed by Microsoft in 1999, it has been serving as a foundation for Windows Media. Its purpose is to store and distribute audio content. Firstly, it was considered as a real alternative for MP3, but then, when ACC appeared, WMA lost partially its significance. It differs fundamentally from MP3 by one realization, and can be installed on an equal basis with other system codecs of Windows 9x.

WMA is characterized by a good compression quality, and therefore it has been adapted later for many audio players, mobile devices, and Playstations. However, due to excessive closure, files in this format cannot be played back on other platforms with satisfactory quality. The new version allows for multi-channel coding of large audio files and coding of voice data. In addition to that, the delay in coding has been significantly diminished thanks to the technology of reduced time dilation.

The name of WMA is being used simultaneously for the file format and the codec. There are some types of the format:

• - WMA, a close analog for MP3;
• - WMA Pro, high quality sound files with wide range of channels;
• - WMA Lossless, for lossless compression;
• - WMA Voice, for compression of voice content into low bitrate files.

According to Microsoft programmers, an audio file of 64 Kbit/s bitrate has a similar sound clarity as the tracks from the original CD. However, some of advanced users do not share such views. Most often, WMA files are generated in Advanced Systems Format which contains both audio and video content. One of the failures is the impossibility to support bitrate of more than 160Kbit/s.

MP4 is one of the most popular formats for multimedia storage and distribution. It is a container for processing of wide data range, from text and graphics to sound tracks and video. Also it is able to support high-quality files, such as 3D-graphics or user’s menus. It is provided in two versions: MPV (for audio) and M4A (for video). A less known extension .mpr is being used for ringtones.

MP4 files may be played by a number of programs, including Adobe Flash, Roxio Creator, Nero Multimedia Sulte, and a default plug-in Windows Media Player. They are adapted for Mac OS and supplied by modern portable players.

MP4/MPEG-4 has been widely used since 2001. By its nature, it is similar with MP3 although more technically complex. It involves AAC coding method and complies with the standards of ISO/IEX 14496-1. Video and audio contained in a MP4 file is usually played in real time. Thanks to extra information (e.g. file name or images) it differs significantly from MPEG. Often it is impossible to embed data in such a file without use of separate streams that commentary tracks are integrated to.