MP3 and lossless compression
MPEG-1 Audio Layer 3, which is more commonly known as MP3, is definitely the most popular lossy audio format out there. Development started in 1987, led by members of Fraunhofer IIS in Germany. It quickly became the unacknowledged standard for lossy audio encoding as it provides high compression rates while still retaining relatively respectable quality. The MP3 format applies a series of filters that remove some upper frequency content. This is often acceptable to the human ear as the upper limits of a human's hearing is considered 20 kHz, with a much lower cutoff frequency being fairly standard particularly as we age. The MP3's biggest advantage is the acceptance it has already achieved. While other formats are trying to gain ground, more audio is being encoded in MP3 format every day. It is widely supported in almost all relevant software and hardware. It also provides fast decoding which is key for efficient playback. Still, it’s performance is a little sub-standard when compared to other more modern formats. It does have a maximum bit rate at which it can rip which may fall below your desire (320 kbit/s) and it’s sampling rate does not lend well to high definition audio (doesn’t support sampling at a rate higher than 48 kHz). Below are alternatives to the MP3: 1. AAC – Advanced Audio Coding. This is the default format for anything and everything Apple, including the iPhone, iPod, and iTunes, but it's supported on pretty much every portable player out there. This format was developed in part by Fraunhoffer IIS, who were the original developers of the MP3 algorithm, and has been touted as the successor to the MP3. It's deviation from MP3 includes: - Supports 48 channels of audio, whereas MP3 supports 2 channels in MPEG-1 mode and 5.1 channels in MPEG-2 mode. - Has a wider bandwidth of sample frequencies. Where MP3 can range from 16 kHz to 48 kHz, AAC can range from 8 kHz to 96 kHz. This is very good for getting an accurate digital representation of the original source. - Higher coding efficiency for both stationary signals and transient signals. - Handles audio frequencies above 16 kHz significantly better than MP3. - Supports a bit rate between 8 and 529 kbit/s. - Supports Digital Rights Management. 2. RA – Real Audio. This format was developed by RealNetworks, the makers of Real Media Player, amongst other things. It's most commonly used in streaming media from the internet. Real Audio supports several different codecs of varying sample and bit rates. It hasn't been widely adopted as a method of transferring digital audio outside of the occasional streaming audio website. The likely cause for this is that there aren't many media players that support the format outside of RealNetworks' own player. 3. Ogg – Ogg Vorbis was initially developed as a response to the MP3 when it was announced that there were plans to charge licensing fees for the MP3 audio format. It is an open-source approach, meaning it is completely free and unrestricted by patents. - Ogg is extremely flexible in the sampling rates it supports, ranging from 1 Hz to 200 kHz. - Ogg also supports a wide variety of bit rates. If you assume a sampling rate of 44.1 kHz (the standard CD sampling frequency), an Ogg encoder will output a variable bit rate between 45 and 500 kbit/s, depending on the quality setting that is specified. - Independent listening tests have suggested that at mid to high bitrates Ogg has better quality than MP3 encoded audio. - Ogg is largely DRM free. 4. WMA – Windows Media Audio is a proprietary format developed by, surprise, Microsoft. There have actually been a few revisions of the original format to create WMA Pro, WMA Lossless, and WMA Voice. This is considered one of the most supported formats, in direct competition with MP3 and AAC. - WMA Standard supports stereo output (ie. two discrete channels). - Offers a sample rate of up to 48 kHz. - At lower bit rates, WMA has been interpreted as better than MP3, although not quite as good as AAC in terms of quality. - At higher bit rates, the differences become less distinguishable. - Supports Digital Rights Management. So you can see the alternatives to the MP3 format are out there. They were all developed as an alternative to MP3 due to perceived disadvantages of the format. Lossy audio is pretty much standard across the internet. As of late, it has seen some considerable popularity as the bandwidth each user has access to increases, as does the storage space available in both computers and portable devices.