Computer file formats compressed files

Figure 9.7. Various linear notation schemes for chemical representation. Some contain only atom types and connectivity (WLN, ROSDAL, SMILES, SLN) and are chemist-readable. Others are compressed versions of molecule file formats (CHIME) and are meant for computer interpretation.

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. 

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. 

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. 

Regardless of whether you choose a lossless or a compressed file format, any files that you intend to make available to listeners using another computer need to employ a format that is compatible with their software. The following is a summary of recommendations on which formats and codec are appropriate for which destinations ... 

Sonic Foundry Audio (. sfa) is a proprietary format from Sonic Foundry that will be available only on computers that have software from Sonic Foundry installed on them. Like some other formats, you can select a number of codecs for compression, meaning that. sfa files can be compressed or uncompressed, using any codec available for. wav format files. 

The. wma format from Microsoft is a direct competitor to the other highly compressed formats in terms of quality. Excellent results can be achieved with any of these formats, but the. wma format has one (some say unfair) advantage over the others in that it is distributed by Microsoft. At this point, it does not have market dominance, but you can be certain that many of your listeners will already have the software to playback. wma files on their computer. 

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