Common digital file formats for transcription of voice to text
Digital recorders allow you to save voice files in different file formats. What format that is often depends on the brand or type of recorder you purchase. Some recorders allow you to save your files as more than one file format. To check what format your recorder saves as simply look at the file extension of your audio file, for example, the three letters file ending after the dot in your file name (e.g., WS30091.wma). Some recorders are ideal for single speaker dictation (e.g., DS2400) where editing and inserting comments after you have dictated is important. Others suit one-to-one interviews or focus group recordings (e.g., DS50) where they have external mics or where omni-directional mics can be purchased as an add-on (ME-30W).
Files saved to CD
.cda (Compact Disc audio file)
We have often been sent .cda files by clients in the first instance. .cda files are not audio files, they are the index files on your CD that point to the audio tracks on it. In order to have the audio transcribed you will need to remove your audio from your CD. If you are unsure how to do this follow these steps:
Insert the CD into your CD/DVD drive and use the ripping facility in Windows Media Player (WMP) to rip the CD or a specific track. There are usually two ways to get the tracks added to your library in WMP. You can add them on with the CD or you can rip them to your PC as .wma or .mp3 files and add those files to your library. It is the .wma or .mp3 version of the file that you will need to send your transcription service. If you ripped the CD by using the rip functionality in the Rip tab in WMP then the files will already be saved on your hard drive by default you just need to locate them!
If you do not have Windows Media Player you can use a software such Express Rip software available at http://www.nch.com.
Uncompressed audio format
.wav (or WAVE, short for Waveform Audio Format): .wav is a very large commonly used file format, however, this file type takes much longer than most when transferring/uploading files to a transcription service. It does, however, produce good quality audio.
Lossless compressed audio formats
A lossless compressed file format takes longer to process than an uncompressed file format and it uses space more efficiently. Lossless compression formats provide a compression ratio of about 2:1.
.mp3 (MPEG Layer-3): .mp3 files are a compressed file format usually associated with music files. The benefit of compressed files is in reduced transfer/upload time when sending it on for transcription.
.wma (Windows Media Audio): .wma file format is owned by Microsoft and is associated with use of Windows Media Player. .wma, whilst being compressed files, retain their sound quality.
.dss (Digital Speech Standard): .dss files are an Olympus proprietary format produced by Olympus recorders. DSS files are said to be 1/12th to 1/20th the size of conventional WAVE files with no reduction in playback quality. This is an excellent file format producing good quality audio.
. ds2 (Digital Speech Standard Pro): .ds2 files are also an Olympus proprietary format, as above. This is the newer, high compression, DSS pro format used by Olympus. Not all transcription software reads this new file format so check with your service provider.
.dvf (Digital Voice File): .dvf files are a Sony proprietary format produced by Sony recorders. Again, this is an excellent file format producing audio with excellent clarity.
Of course all of the above file formats can be used for transcription purposes but each varies in audio quality and file size so bear this in mind when you purchase your digital recorder.
