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Lion
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| Joined: | Thu Mar 6th, 2008 |
| Location: | Mississippi USA |
| Posts: | 25 |
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Posted: Tue Oct 21st, 2008 11:14 pm |
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There are two different types of file compression algorithms.LossyLossless
Lossy reduces the size of the file much more than lossless by discarding information that is inaudible. The human ear can only hear part of the information any given audio file actually contains. By discarding the information that is unnecessary because of your hearing limitations, the file size is reduced significantly.
Lossless reduces the size of the file without losing audio quality. The downside to lossless formats is that they are usually large files. If you want to retain the quality of the audio clip and are not concerned with the size of the file this is the best choice.
Which is which?
Virtually all digital audio files are PCM based, the one major uncompressed format. AIFF (Mac), AU (Unix) and WAV (Windows) are the files used to store the PCM format. When you transcode the WAV file to create a MP3 you are essentially just wrapping it up. The MP3 codec pulls all of the inaudible and unnecessary information out of the WAV and tosses it, then it compacts what’s left, leaving you with a smaller file. (It’s not a good idea to throw away any information, even if your ears can’t hear it, if you are archiving an important audio file. There are many forms of analysis that cannot be performed without the missing data. If it needs to be precise and credible choose a lossless format over a lossy one.)
There are two things working for (or against) you when considering which file format to choose, the format itself and the codec. A codec performs the reading and writing of a file format. So you need a codec to play and write any given file. In terms of usability, codecs limit the use of many formats. For example, in order to transcode a WAV file to MP3 you need to have a MP3 codec installed. Since most MP3 codecs are patented and restricted you are forced to purchase software in order to convert a file you already own to a smaller file that you will be able to easily share. Most people have the ability to play MP3 files at no charge but saving them generally requires an upgrade to the “costs money” version of the program. Luckily there is now the LAME MP3 format. It’s free and once installed will allow you to burn, transcode and play to your hearts content.
(.mp3)
MP3 files which are by far the most common are lossy. This is the format used when most of us listen to music and purchase songs. Like JPEG image format, you are able to choose what quality you prefer when creating a MP3 file. But this is a very lossy format. The more these files are edited, saved and transferred, the more they degrade. This format is protected by numerous patents and is highly restricted. The LAME MP3 codec is a newly developed codec that is free to install and use with no need to purchase proprietary software.
(.wma)
WMA files are Windows based, Windows Media Audio format, owned by Microsoft. There are lossless and lossy algorithms available for the WMA format.
(.aac)
AAC files are lossy or lossless and based on MPEG2 and MPEG4 standards. They have been popularized by iTunes, which converts WMA files to AAC (MPEG4 based and owned by Apple) before loading them into it’s library. This is also a format favored by the iTunes Store. Arguably, the quality of the AAC format is slightly superior to the more common MP3, the difference is inaudible for the most part.
(.ogg, .oga)
OGG files are more common on Linux based systems as it is a free, open source lossy container format. They support many different codecs but the most popular is Vorbis. Vorbis is comparable to MP3 in quality, but more often superior. Since this format is used less it is not always the best choice for sharing even though it is a completely free (MP3 is not free) and of higher fidelity. The Ogg Vorbis combination is an extremely good format, offering higher fidelity than MP3, AAC, WMA and many others.
(.aa3, .oma)
ATRAC is a proprietary format owned by Sony. There are lossless and lossy versions of this format.
(.mpc)
MPC files are another lossy format, known as Musepack or MPC which is open source. (This format was known as MP+, MPEG+ or MPEGplus) Notable are the double-blind studies done on lossy audio codecs, finding Musepack and Ogg Vorbis to be the best available audio codecs for high-quality lossy audio compression. Again this format is used less than other formats so it is not always the best choice for sharing.
(.flac)
FLAC is lossless and the best choice for archiving audio files. The downside is the files are large. It was adopted by the European Union for audio archival. It is also used by many modern video games with high fidelity musical scores such as HALO, where the soundtrack is actually symphonic as opposed to just computer generated. It works like a ZIP file but in an audio format, allowing you to extract an exact copy of the original file.
(.ape)
Mon_key’s Audio files are lossless. It is similar to FLAC in quality but the license is different (still free) and only supported on Windows based systems. You can use Mon_key’s Audio files on any Operating System but the software is not official. The file size is comparable if not slightly smaller than the FLAC format. (There is no _ in Mon_key's, this board changes the word to primates...)
(.wav)
WAV files are the standard audio file container format, mainly used in Windows Operating Systems. The file size is large (10MB per minute as opposed to 1MB as with MP3) (uncompressed)
(.aiff)
AIFF like WAV for Macs. (uncompressed)
(.au)
AU is the standard for Java, Sun and Unix environments. (uncompressed)
(.dct)
DCT file format was designed for dictation and is primarily used in the medical profession where confidentiality is an issue. These files can be encrypted (required by law in most cases for the medical field) and contain header information pertinent to the creation of the file.
Summary
Recording AudioYou are probably stuck with whatever your recorder will allow, usually MP3/WMA if digital. Make sure to save (or transcode) the file to the format that suits the purpose of the audio file. Sharing AudioGo with MP3 when you need it small and are just sharing. (email, internet)Go with Ogg Vorbis when you need detail and aren't worried about the guy who can’t play it. After all they should keep up, the codec and players are free. Archival
Go with FLAC. The files are large but you won’t loose a thing. (as I write this a 500g external hard-drive is only $100 and the prices are steady dropping)Or any format that is lossless and suits your file size requirements will work. This isn't an exhaustive list of formats, just the most common and most useful so far.
If I left anything out that you feel needs to be added, post it.
Last edited on Tue Oct 21st, 2008 11:18 pm by Lion
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“All are lunatics, but he who can analyze his delusions is called a philosopher.”
~Ambrose Bierce
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tennesseecherokee
Member
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Posted: Sun Nov 30th, 2008 08:10 am |
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| This Mississippi boy sure knows his digital audio compression stuff ! Lion, I just now saw your post--forgive me for not finding this earlier because it contins a great deal of informative and useful information. I sure hope that Watch 1 and 7 Fireflies see this cause they are audio buffs too . Wish I would have noticed this before meeting you at the Alabama get together so I could have gotten you to explain this in even greater detail. Thanks again for sharing your knowledge and it was a pleasure to have gotten the opportunity to meet you and your brother.....TnC....
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We will be known forever by the tracks we leave behind.
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