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Understanding Digital Formats Part 2: Microsoft's WMA Format and the Rest of the Field

[Based on an article by Matt Whitlock on Techlore.com]

Sansa players can use music files in two common formats: MP3s and WMAs (including the secure WMA audio files used in many online store purchases). They do not use a range of other less common formats, including AAC, OGG, and ATRAC.

So we have some questions to answer: What format are we going to store our music in? And, do we lose anything if we buy a music player that doesn’t use the less common formats?

Here are some basics that may help you understand digital music formats, and make the decisions you need to make.

  • In Part 1, we discussed some basics of digital formats and compression, and look at the main format used today: MP3s.
  • Here, in Part 2, we will look at the other digital format used by Sansa players, Microsoft’s WMA and we will briefly look at other formats that Sansa players can not play.
  • And in Part 3, I will offer basic advice on which format to use.

First, Microsoft’s WMA

The simple fact that the mega-corporation Microsoft (and its software Windows Media Player) promotes WMA means that this format is widely used. And the truth is that it has some advantages.

WMA is the abbreviated term for Windows Media Audio. WMA is comprised of many different levels of compression, with each handling the compression of the original audio differently.

Not surprisingly, Microsoft argues that its product is simply better. You can listen to their examples and make up your own mind. The fact is that at the higher bit rates MP3s and WMA have quite similar quality – the differences between them are small.

However a number of independent researchers argue that at bit rates under 128 kbps, they feel WMA sounds better – though most reject Microsoft’s claim that its files are “CD quality” at 128 kbps.

WMA is not just a lossy encoder like MP3 because it offers many different kinds of compression tools in one package. A brief explanations of its options is below:

WMA -- Similar to MP3, this lossy codec compresses audio information to a specific bit rate at the encoding stage. Also like MP3, there are many different bit rates to choose from.

WMA VBR -- VBR stands for variable bit rate, which means that the encoder will detect and encode harder passages at a higher bit rate, and the easier passages at a lower bit rate. This method helps keep the file size small, but more efficiently uses the space to make everything sound better. Many devices handle VBR, but there are still many that do not.

WMA Lossless -- The lossless version of the codec ensures that no audio information is lost in the encoding stage. When these signals are decompressed, the result will be exactly the same quality as the original source. Lossless always uses variable bit rates, but the resulting file sizes are still large.

WMA Voice -- WMA Voice is designed specifically for encoding voice signals like e-books and radio. Since these signals do not require a huge amount of space to begin with, WMA Voice compresses these to a very small file, which will playback at fantastic quality.

If you save CD music as WMA files (using, for example, Windows Media Player on your computer) the software will allow you to manipulate the VBR

Formats not used by Sansa:

AAC (.mp4, .aac, .mpe)

AAC stands for Advanced Audio Coding, which is part of the MPEG-2 AAC standard. AAC has been highly popularized by Apple, who uses this standard in their wildly successful iPod portable music player. The latest version, MPEG-4 AAC, includes additional tools for even better quality compression.

AAC is a more advanced and efficient codec than MP3. It yields better quality results, especially at lower bit rates. Like WMA, it also supports variable bit rate encoding.

AAC, though successful due to the iPod, is not one of the most compatible compression formats in the market. Other than Apple's iPod and their QuickTime Media Player, few portable and software players support this format.

OGG (.ogg)

OGG is the nickname for Ogg Vorbis, which is an open source, royalty free audio compression format. OGG has gained ground since its launch, mostly because it produces exceptional quality results, and is completely free for manufacturers to implement in their hardware and software players. OGG contains many of the same features that the major formats like MP3, WMA, and AAC contain, as well as a few unique features to itself.

Though it's the most popular of the free formats, it has a long way to go before it becomes a widely compatible format. Most of the software players have a plug-in to support OGG, but few portables devices play OGG files right off the shelf.

ATRAC (.atrac)

ATRAC stands for Adaptive Transform Acoustic Coding, and was initially developed by Sony in 1991 for the MiniDisc. The original ATRAC format does not reduce the size of the original file anywhere near as much as other formats. However, since ATRAC was developed for the MiniDisc, it was successful in packing the same playing time of a CD onto a MiniDisc, with the sound quality nearly indistinguishable from the source. The higher compression versions of ATRAC made their debut in 2000 and 2003, which were designed to pack more playing time on a MiniDisc. However, the discs would remain unplayable in older MiniDisc players.

The ATRAC format is only compatible with Sony portable audio products. In many cases, it is the only audio format it will accept. Owners of these products use bundled software to convert other audio formats to ATRAC before it is loaded into the player. With Sony's recent announcement to begin offering native support for MP3, it is likely that the ATRAC format will quickly be phased out.

In Part 3, We’ll share some advice on which formats to use.

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