MPEG-4 is one of the latest standards for compression of digital audio-visual media developed by the Moving Pictures Experts Group (a division of the International Organization for Standardization or ISO). Every time a new MPEG standard is set, software developers and hardware or device manufacturers make their new products compliant. Consumers don't necessarily go out and buy these new devices. In such cases, it is up to the consumer to find a way to convert media files formatted in the new standard to previous formats to be able to play them in their old devices.
- File extensions. MPEG-4 files are given the .mp4 extension. This doesn't really signify whether it is an audio file or a video file with audio data. For this reason Apple started using and popularizing the .m4a file extension to indicate that a particular MPEG-4 file is just an audio file. The .mp3 file extension on the other hand refers to files that are formatted in the MPEG-1 Audio Layer 3 standard. MP3 is not short for MPEG-3. In fact the MPEG-3 standard was discontinued as its improvements were simply incorporated into MPEG-2. MP3s are strictly audio files. Thus easy conversion from MPEG-4 to MP3 is possible between audio files. Before you attempt to convert an MPEG-4 file make sure that it is an audio file or that it has the .m4a file extension.
- Use an online service. The problem of converting MPEG-4 to MP3 is actually quite common and thus many sites have put up such a service on the Internet. They work in similar fashion to websites that offer PDF to Doc conversion. On these sites, there is usually an input field with a Browse button beside it. Clicking on that button will allow you to search and input the MPEG-4 file stored in your hard disk. Then there is a separate input field usually with a dropdown list which will allow you to choose the resulting format of the conversion. Finally there will be an OK button or its equivalent which you can click to start the conversion process.
- Use a digital audio editing software. Fully featured applications of this type can typically load audio data of various formats and output them in a different one. They can therefore be used to convert MPEG-4 to MP3. Use a fairly recent version of this kind of software to make sure it does read MPEG-4 audio files. The general procedure is to use the Import or Open file function to load the MPEG-4 audio and then use the Export or Save As function to output the audio in a different format. Usually when exporting or saving, a dialog box will appear on which you can set options for format and bit-rate. Choose the .mp3 format and set the bit-rate at 128 kbit/s (kilobits per second), the typical MP3 bit-rate. MP3s can actually have a higher bit-rate and if the application allows for it, you can also set the output file at a higher level. This could improve the audio quality of the outputted MP3 file.
Before attempting any conversion, you might want to first make a copy of the original MPEG-4 file. Audio format conversions are often irreversible. If something goes wrong, you'll at least be able to begin again using a different method.