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Important Notice: Although XO Wave will continue to be available for some time, it will be discontinued as we prepare to bring you the next generation Digital Audio Workstation. The new software we are developing is called Xonami and it will have many, but not all, of the features of XO Wave. A discount upgrade path will be available for users who purchased XO Wave September 1st, 2010. We realize that there are few professional CD mastering options with the full range of capabilities offered by XO Wave, so we will continue to offer the package as long as possible. However, please keep in mind that as discontinued software:
For up-to-date information about our upcoming software, please join our mailing list. XO Wave: Importing and Exporting Audio
The ability to import and export audio in standard formats is essential to any audio package. XO Wave Open users can import and export industry-standard AIFF and WAV files. XO Wave Free users can additionally import any format that QuickTime supports. XO Wave Pro adds QuickTime export, including video formats. Audio File FormatsThis section provides a brief overview of some of the popular audio file formats, with information about their quality. If you are familiar with audio file formats, you may want to skip it. Uncompressed File FormatsAIFF and WAV files are the two most popular uncompressed audio formats. We won't get into the details here but, generally speaking, uncompressed means that there is one, fixed size piece of data in the file that represents each audio sample. The two factors most important to the quality of an uncompressed file are its sample rate and bit-depth. Although the details of file structure and data formatting are different between AIFF and WAV, at a given sample rate and bit-depth, their audio quality is the same. Bit-depth: Bit-depth is the number of bits ("BInary digITs") used to represent each sample of audio. Common bit-depths are 8, 12, 16, 20 and 24. 32 is less common, but supported in some software, including XO Wave. In general, files with higher bit-depths sound better because they have less noise, but require more hard disk space and processing power. Because most audio file formats actually segment data into 8-bit chunks, 12-bit and 20-bit files must normally be repacked as 16-bit and 24-bit respectively. As a result, such files offer no effective advantage over their higher-quality cousins, and should normally be avoided. Because CDs use 16 bits, 16-bit audio is often used as a benchmark for audio quality. As a rule of thumb, you'll want to use higher bit-depths for recording and any intermediate files you create, but 16 bits is fine for a finished product, as long as proper dithering is used to create the 16-bit file. Thanks to high quality lossless and lossy compression, the days of sub-16-bit audio are pretty much over, so always try to use at least 16-bit audio when using an uncompressed format. See our tech note on resolution for more details on the subtleties. Some file formats support "floating point" or even "double-precision floating point" formats, which are closer to the formats used internally by software such as XO Wave. While these formats are, in fact, of very high quality, the actual quality of these formats is often overstated. A floating-point file is superior to a 24-bit file, and a double-precision file is superior to a 48-bit file, but not too much more than that can be said without getting very technical. The AIFC file format supports floating-point audio. Sample rate: Sample rate is the number of samples used per second. As with bit-depth, more is generally better, but in this case, instead of reducing noise with higher sample rates, you improve the frequency response. Higher sample rates generally require more disk space and more processing power to play back and process. Some people advocate using the highest sample rate available during production and reducing the sample rate when you produce your final, finished product. While this may produce superior results in some cases, changing sample rates at any time can degrade the sound quality, so if your project is targeting CDs, which have a sample rate of 44,100 Hz, you'll want to use that sample rate throughout your project. In general, we recommend 44,100 Hz for music and CD projects and 48,000 Hz for video projects, because these rates are standard for these types of projects, and using these rates will minimize the number of required sample rate conversions. Technically speaking, human hearing does not exceed 20,000 Hz, which can be represented with a sample rate of 40,000 Hz. A slightly higher rate is required to reduce some of the artifacts of conversion from analog to digital signals, which is why CDs use 44,100 Hz. Listening tests have conclusively shown that higher sample rates sound better, which has caused some pros to advocate using higher sample rates in digital audio. However, above 48,000 Hz, the gains are small compared to the costs. For example, with a sample rate of 88,200 Hz, you may achieve slightly better sound quality at the expense of doubling your hard disk and CPU requirements. This cost, along with the fact that it is very hard to deliver 88,200 Hz audio to most listeners, leads most people to agree that it is rarely worthwhile to use sample rates over 48,000 Hz. If the DVD audio standard catches on, we might see a rise in popularity of high sample-rate audio in the future, but until then, there's not much point. Lossless CompressionFile formats which offer true lossless compression, such as FLAC and "Apple Lossless", sound identical to uncompressed files, but take up less disk space. However, because the disk space saved is relatively small (usually around 50%), and because a lot of CPU time is required to compress and decompress these files, they are used much less frequently than lossy formats. Lossy CompressionFile formats which offer lossy compression -- such as MP3, AAC, and Ogg Vorbis -- sacrifice a small amount of audio quality for a large savings in disk space. High-quality MP3 encoders can be used to create a file that is difficult to distinguish from the original, with a dramatic reduction in disk space. (Another way to look at this, of course, is that compressed files allow you to have much more audio of a given quality in a given amount of space.) These formats use psycho-acoustic models of human hearing to distinguish between noticeable and imperceptible information, leaving out the latter to produce smaller files. Ideally, the compressed version sounds no different from the original. While no compression scheme actually meets this ideal, recent encoders have gotten very good at sounding like the original. Obviously, the small file size of compressed audio can be fantastic for finished products that people want to download quickly, e-mail, or even put on their phones. However, such files should never be used as intermediates in professional audio production because the distortion caused by compression may produce artifacts after further processing. Moreover, the distortion created by each compression step may be cumulative. So, you may not notice the difference between a CD version of a song and an MP3 you "ripped", but it could become obvious after applying EQ or other effects to the track. The assumptions about what you can and cannot hear that are made by encoders assume that you will not be doing further processing later, so remember not to process compressed files. As for the question everyone always asks (that would be, "which format is best?"), I'm afraid the answer is: it depends. There are people who claim that AAC is best, or Ogg Vorbis, or MP3, but in general there is no one right answer. With most file formats, the real determining factor of the quality of the compressed files is the quality of the encoder. It is possible (and common) to have multiple MP3 files of the same size, created with the same source files, that sound very different because different encoders were used. For MP3, LAME is a very highly regarded encoder, and many feel it rivals everything else. There is very little doubt that it rivals iTunes' built-in MP3 encoder. For Ogg Vorbis and AAC, you don't have as much choice, but the encoders in use are consistently high quality. Most audio encoders give you some options about how to compress your files. These options generally provide a trade-off between sound quality and file size. In general, you can't get a better-sounding MP3 from any particular encoder without making a larger file. Importing AudioBefore an audio file can be imported into XO Wave, it must first be prepared. For example, it may need to be moved or copied into your session folder, or converted from one format to another. In addition, XO Wave needs to build waveform overviews to speed up drawing of the audio waveform. To start preparing an audio file for XO Wave, you must import it. Because importing audio can take time, especially when importing a lot of audio, audio import is an offline operation in XO Wave, meaning that files can be imported in the background while you work on other things. There are several ways to start an import:
After starting an import, XO Wave will work on copying and creating overviews in the background. When it is finished, it will give you several options for importing which will vary depending on the particular menu command used. Options may include placing the files in order on a new track and creating CD Track Markers, or creating one new track for each file. In either case, at completion of the import operation, your Undo list to be cleared (cancelling before completion avoids the Undo clearing). XO Wave can also import metadata associated with the files, such as artist and song title information. This information can be viewed, edited, and used for creating CD Text information. Exporting AudioWhen your work on a session is complete, you'll usually want to export it, a process which renders all audio into a single file which can be read and played back by other programs such as iTunes, QuickTime Player, and even web browsers. XO Wave Pro users have additional options for exporting the audio along with video if the session has an associated video file. For more info on working with video in XO Wave, see our tutorial, Editing Sound for Video and Film. Note that available options for exporting depend on various factors, including XO Wave version, the presence of an associated video file, available QuickTime plug-ins, and which specific Export command is used. When the session sounds the way you want, you can export it to a variety of formats. Like importing, exporting is an offline operation, which won't prevent you from doing other work. Here's how to export your session:
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