[linux-audio-user] Is there a way to compress the size of a wave file?
lists at pelvoux.nildram.co.uk
Thu May 12 04:18:39 EDT 2005
On 12/05/05 04:09:15, Flash Love wrote:
> I recorded a one hour audio session using windows Sound Recorder for a friend
> and much to my chagrin and my friend's dismay, the Audacity edited file is
> over 400M!
400Mb is about right for about 40 mins of uncompressed audio (the original 1 hour session, uncompressed would be 605Mb. If the WAV file you started with was smaller than that then it musthave been compressed.
There are ways to compress the file; some are lossy, i.e. they throw away parts of the sound that the designers don't think you could hear, and some are non-lossy, i.e. when you uncompress it you get the original back exactly.
The most well known lossy format is MP3 altough OGG Vorbis is a popular choice particularly with supporters of free software as it it patent-free. There is software available for Linux to compress to either of these formats. With lossy formats you can choose how much gets thrown away and therefore how much compression you get. In some cases you choose the bitrate and in others you choose a quality factor. As an example 128Kbit MP3 achieves a typical compression of about 1:10, i.e. the compressed files are about 1/10 the size of the original. WMA (windows media) and AAC (DVD sound tracks) are also lossy formats.
There are a variety of non-lossy formats too but the one that seems to be popular on Linux is FLAC. The compression you get varies slightly depending on the source but is typicaly 1:2 i.e. the compressed files are half the size of the original. This compression ratio is fairly typical of non-lossy compression.
My personal choice is to keep things I intend to edit further or transfer to CD in WAV (uncompressed) or FLAC format and music in it's final form that will be listened to direct from the PC in Ogg Vorbis with -q 6.
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