What is an MP2 file?
An MP2 file, also widely known as an MPA file, is an audio format compressed using MPEG-1 or MPEG-2 Audio Layer II. This lossy audio compression standard was formally defined by ISO/IEC 11172-3, which also established the MPEG-1 Audio Layer I and the vastly more popular MPEG-1 Audio Layer III (MP3). The primary goal of the MP2 format, like its counterparts, was to significantly reduce audio file size. While the MP3 format gained greater mainstream adoption due to its smaller file size and widespread availability online, the MP2 file remains a critical and resilient standard, particularly within the professional realm of audio broadcasting where its specific technical strengths are essential.
MP2 File Format
MPEG Audio Layer II (MP2) is the core algorithm of the MP3 standards. MPEG-1 Audio Layer 2 encoding was obtained from the MUSICAM audio codec. It started as the Digital Audio Broadcast (DAB) project in Germany as a part of the EUREKA research program. The Eureka 147 contained three main elements: Transmission Coding & Multiplexing, COFDM Modulation and MUSICAM Audio Coding (Masking pattern Universal Sub-band Integrated Coding And Multiplexing). The MUSICAM was one of the few encodings which was able to achieve high audio quality at bit rates in the range of 64 to 192 kbit/s per monophonic channel. The goal was to provide low delay, low complexity, error robustness, short access units and fulfill the technical requirements of broadcasting, telecommunication and recording on digital storage media.
MP2 is a sub-band audio encoder, which can compressed in the time domain with a low-delay filter bank generating 32 frequency domain components. By comparison, MP3 is a transform audio encoder with hybrid filter bank, which means that compression applied in the frequency domain after a hybrid transformation from the time domain. The MP2 encoder may exploit inter channel redundancies using optional “joint stereo” intensity encoding.
Key Characteristics of MP2 Files
| Characteristic | Description |
|---|---|
| Broadcasting Standard | MP2 is the mandated audio codec for numerous international standards, including DAB (Digital Audio Broadcasting) and DVB (Digital Video Broadcasting). |
| Less Aggressive Compression | It typically operates at higher bit rates (192-384 kbps) than MP3, prioritizing audio fidelity and robustness over small file size. |
| Open and Royalty-Free | The patents related to MP2 have expired, meaning it is now a completely free-to-use format, which reduces costs for broadcasters. |
| Computationally Less Intensive | While encoding is complex, decoding MP2 requires less processing power than decoding MP3 or AAC, making it suitable for a wider range of consumer receiver hardware. |
| Niche Professional Use | While largely superseded by MP3 for music and AAC for general purpose, MP2 remains deeply entrenched in professional broadcast chains and archival systems. |
MP2 File Format Specifications
The MP2 file format is based on successive digital frames of 1152 sampling intervals with four possible formats:
- mono format
- stereo format
- intensity encoded joint stereo format (stereo irrelevance)
- dual channel (uncorrelated) format Some important technical specifications of MP2 are given in the table below:
| Specification | Description |
|---|---|
| Sampling rates | 32, 44.1 and 48 kHz |
| Bit rates | 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320 and 384 kbit/s |
| Additional sampling rates | 16, 22.05 and 24 kHz |
| Additional bit rates | 8, 16, 24, 40 and 144 kbit/s |
| Multichannel support | Up to 5 full range audio channels and an LFE-channel (Low Frequency Enhancement channel) |
FAQ
Q1: Is MP2 better quality than MP3?
A: At the same bit rate, MP3 is generally more efficient, but MP2 often provides more robust and reliable audio quality in professional broadcasting and editing environments.
Q2: Can I play an MP2 file on my media player?
A: Most major media players like VLC, MPlayer, and Foobar2000 support MP2, but it may not be compatible with some default music apps on mobile devices.
Q3: What is the main use of the MP2 format today?
A: Its primary use is in digital television (DVB-T, DVB-S) and radio (DAB) broadcasting systems worldwide.
Q4: Why did MP3 become more popular than MP2?
A: MP3’s more aggressive compression algorithm created smaller files with acceptable quality, making it ideal for personal music storage and early internet streaming.
Q5: Are MP2 and MPEG-2 Audio the same thing?
A: They are closely related; MPEG-2 Audio includes backwards-compatible extensions to MP2 (like support for lower sample rates), but the core Layer II codec is the same.
