File Types

Examples of different file formats and some details about them follow:

WAVeform Audio (.wav)
WAVeform Audio (.wav) is a common file format and was one of the first audio file types developed for use with the PC. It is lossless, but generally very large.

WAV Warning!
Not all wav files are the same! Although they all end .wav, depending on the recorder, you and your VA may need a special ‘codec’ to play it back. An example is Sanyo – a popular and moderately priced recording system but one that records specifically Sanyo wav files. You should check that your VA has the ability to transcribe Sanyo wavs. If not, Sanyo may oblige by sending out the relevant codec on CD, if you ask them nicely!

The following types are all lossy, but generally the sound quality change is negligible and you will save significant time and money with reduced transfer times. This is not an exhaustive list of all audio file types – there are a huge number. It aims to cover most of the types recorded by available transcription software.

MPEG-1 Audio Layer 3 (.mp3)
This is a compressed WAV file often used in music. Many digital recorders will also record mp3 or allow you to record WAV and then compress to mp3. The compressed files will be around a twelfth the size of WAV files.
    
Windows Media Audio (.wma)
Windows Media Audio (.wma) was developed for Windows Media Player which is bundled with all Windows-based PCs these days. It is even more compressed than an MP3, to about one thirty-sixth the size of a .wav, but apparently retaining the original sound quality. I have to say that in my experience I am not sure whether or not this has always been the case.
  
Digital Speech Standard (.dss)

In my experience, most playback software used by Vas will play .dss files. I believe .dss was developed by Olympus and almost all Olympus recorders will record .dss files. Lanier and Grundig recorders also generally use .dss. The file size is reduced by twelve to twenty times, as compared to a WAV file.

Encrypted dictation (.dct)

Often used for medical transcription, which requires very high confidentiality, these recordings are encrypted at the recording end and need to be decrypted on receipt. A wide variety of playback software will deal with these files.

TrueSpeech from DSP Group

TrueSpeech, from the DSP group, was designed for personal computers and personal communications devices. It has very high compression ratios ranging from 15:1 to 27:1. If you are able to record this format it is probably best restricted to use with dictation or one-to-one interview in a quiet environment. It is probably too lossy for focus groups etc.
There are a whole host of other file types available so don’t worry if the type that your machine produces is not listed above. Contact your VA and s/he will probably be able to assist you, or at least point you in the right direction.

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