Protected AAC and MP3 Formats
AAC is the default audio format of Apple's iPhone, iPod and iTunes. Most of the music in iTunes Store is in AAC format. Sony PSP also adopts AAC as its audio standard format. However, AAC is not supported by all media players. If your media player is not compatible with AAC, especially the DRM protected AAC audio, you have to convert the AAC files to MP3 or WMA, or other unprotected audio formats that can playback on your audio player.
MP4 is the filename extension for MPEG-4 Part 14 files. It's a multimedia container to store audio and video streams with subtitles information. Almost any kind of data can be embedded in mp4.
MP4 was extended from Apple's QuickTime MOV format. Devices that play mp4 files are referred to as MP4 players. Apple Inc. started using and popularizing the .m4a file extension. Basically, there are no typical differences between m4p and m4a. MP4 files encrypted by FairPlay DRM as sold through Tunes Store use .m4p extension.
An MP3 file is made up of multiple MP3 frames, which consist of the MP3 header and the MP3 data. This sequence of frames is called an Elementary stream. Frames are not independent items ("byte reservoir") and therefore cannot be extracted on arbitrary frame boundaries.
The MP3 data is the actual audio payload. The diagram shows that the MP3 header consists of a sync word, which is used to identify the beginning of a valid frame. This is followed by a bit indicating that this is the MPEG standard and two bits that indicate that layer 3 is used; hence MPEG-1 Audio Layer 3 or MP3. After this, the values will differ, depending on the MP3 file. ISO/IEC 11172-3 defines the range of values for each section of the header along with the specification of the header. Most MP3 files today contain ID3 metadata, which precedes or follows the MP3 frames; this is also shown in the diagram.
Converting Protected AAC to MP3
NoteBurner Protected AAC to MP3 Converter is an excellent audio conversion tool that can help you transcode protected AAC to MP3, WMA and WAV formats. Working with iTunes, NoteBurner protected AAC Audio Converter can convert protected AAC to MP3, protected AAC to WMA and protected AAC to WAV. Since NoteBurner Protected AAC to MP3 Audio Converter works as a virtual CD writer. It can convert almost all music formats that your media player software supports. It supports almost all media player software such as iTunes, Windows Media Player, Real Player, and Napster.
AAC is a wideband audio coding algorithm that exploits two primary coding strategies to dramatically reduce the amount of data needed to represent high-quality digital audio. 1. Signal components that are perceptually irrelevant are discarded; 2. Redundancies in the coded audio signal are eliminated.
AAC offers sampling frequencies between 8 kHz and 96 kHz and any number of channels between 1 and 48. AAC encoders can switch dynamically between a single MDCT block of length 1024 points or 8 blocks of 128 points.
NoteBurner AAC Audio Converter converts any DRM protected music files (such as M4P, M4A, WMA, M4B) and DRM-free audio files to MP3, WAV and WMA formats. NoteBurner DRM Audio Converter can preserve MP3 ID3 tag, containing Artist name, Song title, Year and Genre of the current audio file. The latest version of NoteBurner can also preserve album name and album art to the converted audio files.
