Audio file formats

The final song can be rendered (saved) to a number of file formats. It isn t really a matter of one being better than another, hnt your choice of a file format should be based on three factors  

The rest of this discussion refers to some of the most common formats, but you may have more or less, depending on the software installed on your computer. 

For files that will remain on your computer, you should select a lossless file format. This means that the file will retain 100 percent of the quality and will not be compressed. Any file format on the Save as type list that you can save to can also be played back on your computer . aif,. sfa,. pca,. w64, and. wav formats are all appropriate selections. 

Compressed file formats are for use when you need to create smaller files for transmission on the Internet or for spacesaving reasons on your computer. All compressed file formats result in some reduction in quality, although this reduction can be very minor to inaudible. The balance between file size and quality is a delicate one that requires some experimentation and experience to execute properly. Some compressed audio formats are. mp3,. ogg,. rm, and. wma. An additional consideration for compressed files that are destined to be distributed over the Internet is whether the format can be streamed. 

While file formats are recognizable by the file extension (such as. wav,. txt or. html), audio and video file formats may also be wrappers around the real format (or codec) of a file. For example, a. wav file might use the PCM (uncompressed) format or the MPEG Layer-3 format. See the section on codecs for more information. 

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Early computer software used to play music yms limited to WAV (binary waveform audio file format) and textual MIDI (musical instrument digital interface) files and, while interesting, was not widely used. Better file formats, in particular, MP3 (MPEG-1 audio layer 3) files, have produced high-quality reproductions that are small enough to download and store easily, and this has greatly increased audio player software. Early video software also was limited by file... 

On the Summary tab, enter the optional song composition, engineering, and copyright information. Some audio file formats you create for publication will save this information along with the song. Otherwise, this information is for... 

Macintosh AIFF (. aif) is the standard audio file format for Macintosh computers, just as. wav is for Windows. It is a lossless file format that preserves the quality of your audio, hut it creates rather large files. 

Files are the most basic unit a typical computer user works with. Files could be text documents (. txt), pictures (. bmp), or songs (. mp3). Media files (see Figure 2.1) are just files that contain audio, video, digital music, or pictures. In the context of ACID, media files that can be used are video, audio, or MIDI in nature. Audio files are paramount, however (see Figure 2.1). Some typical file formats for audio that can be used in ACID are. wav or. mp3. 

Windows Explorer showing a file folder that contains Windows audio files in the WAV (. wav) file format. 

MIDI and video files are obviously not proper loops and, therefore, will not be referred to as such in this book. As important media components of ACID, each has a chapter devoted to it later, but they will be ignored for now. Instead, the rest of this chapter is going to discuss audio files, which might all be called loops, whether they loop or not. The most popular format for audio files used as loops is the Windows. wav file format. To Windows or another audio application, the. wav files that go into an ACID project all look the same. That is to say, although ACID has three different types of audio tracks and thus three different kinds of audio loops, Windows sees these as all the same. The information that ACID uses to separate these types is proprietary to ACID. 

Do not construe this to mean that you cannot use other companies loop files and libraries in ACID. Just about any audio file in any of a large number of popular formats can be used in ACID. These files will not have the beat, pitch, or tempo inherent in an AQD loop, so they will not automatically be adjusted by ACID to match the project— but they will certainly work as well as any other audio file. ACID will take its best guess about tempo and beat information and will very frequently get it right, but pitch information will not be detected. All of this information can be added by the user, as detailed later in this chapter. 

All audio files on a computer are digital. Regardless of the format or encoding used to convert an analog audio source to digital, some information is going to be lost in the digitization (quantization) process. This loss may be inaudible on a subjective level and may even be considered theoretically undetectable by humans, but there is an inherent loss of information nonetheless. There are three major variables that influence quality and file size sample rate, bit-depth, and the number of channels. 

OggVorbis (. ogg) is another relatively new compressed media file format that is appropriate for audio delivered over the Internet. It is an open-standard audio format that can be freely used by anyone. Most other codecs, notably. mp3, require some type of payment for their use (in most cases, you automatically pay when you buy software like ACID). OggVorbis yields high compression ratios, maintains good quality, and supports streaming. This is an excellent format, but, at the time of this writing, it is not as widely distributed as the. mp3 or. wma formats. 

Sonic Foundry Perfect Clarity Audio (. pca) is another proprietary format from Sonic Foundry. This is a newer and more advanced format that compresses files losslessly. This means that the file size of a. pca file is considerably smaller than standard uncompressed file formats while retaining 100 percent of the original file quality. For audio files that will remain on your computer, this is an excellent choice, since you can save disk space without sacrificing quality. Use caution when distributing. pca files to others, because they won t be able to use them unless they have Sonic Foundry software installed. The amount of lossless compression depends on the complexity of the project and the source media used, but it can typically result in a file-size savings of 30 percent or so. 

As hinted at in the previous discussion of file formats, the real decision about how to render your final song boils down to compression. The first question is Do you need compression If yes, then the second question is What kind Audio compression is considerably easier than video compression, and the choices you have are really between a number of compression methods that all produce quite good results. While this may seem like a fairly complicated topic at first, always keep in mind that you can almost always get away with picking a compression method and selecting a template without a second thought. 

Lossless means no loss of audio information. It is possible in many situations to eliminate unnecessary data from a computer audio file without losing audio information. This means that an audio file can be compressed in size while still maintaining 100 percent of the original file s audio quality. The Sonic Foundry Perfect Clarity Audio (. pca) format is an example of a lossless yet size-compressed file format. 

A number of formats allow the listener to play back the audio file while it is being downloaded without a special streaming server. 

The first CD standard, called the Red Book standard, is the standard for recording digital audio (audio CDs that you play in your home CD player). It specifies the recording level as 16-bit, 44.1 KHz, and that the entire disk will have an index of the music tracks stored on it. The Yellow Book standard defines the main requirements for data storage on a CD-ROM. This standard supports both PC (ISO9660) and Mac (HFS) file system formats as well as file system formats from other vendors (DEC and VMS). 

If you want to create an audio CD that others can play on their home stereo or car CD players, the standard Windows Wav (. wav) format is a good choice. The quality is very high, but these files are far too large to e-mail to friends or post on the Internet. 

If you want to publish your song on the Internet, the Windows Media Audio (. wma) or MP3 Audio formats are good choices. Small file sizes at the price of some quality make these formats ideal for e-mail as well. 

The. mov format is, as its name suggests, primarily a movie or video format, but you can also create. mov files that are audio only. The Include video option needs to be checked for all video projects. 

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