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Subject: FLASH: Re: FLASH .wav files-not all equal?
From: Dave Hollinden
Date: Mon, 29 Mar 1999 19:41:53 +0100

Stick to PCM. PCM means "pulse coded modulation" and is the basic format for digitized audio. ADPCM is "adaptive differential PCM" and is a format for compressing PCM. MPEG-3 is another method for compressing PCM. And Flash doesn't contain any algorithms for uncompressing compressed audio, so always use straight PCM.

Also, I get the feeling from some recent letters on the list that there is some confusion between reducing audio sampling rates and compression. Audio compression takes place when you apply a compression algorithm to a file, such as ADPCM, MPEG-3, Shockwave audio, etc. The file is made smaller, and then needs to be processed by a decompression algorithm to be played. On the other hand, you can reduce file size by reducing the sampling rate and bit depth of the audio file (making it 22 or 11kHZ rather than 44kHz, or 8 bit rather than 16 bit). This is not compression, and thus doesn't need a decompressor for playback. This is decreasing the amount of information, and thus the quality, by reducing the amount of data points and the number of bits is each data point. The parallel to this in the graphics world is reducing the number of dots or pixels per inch in an image, and reducing the number of bits used to represent each point in the image. Making a 24 bit bitmap into an 8 bit file makes it smaller by reducing it's overall resolution, but making it a JPEG makes it smaller by compressing it. See what I mean?


At 12:54 PM 3/28/99 -0500, you wrote:
I subscribed to a sound effects site, downloaded several .wav files and then proceeded attempt to load several into Flash. Some loaded, some did not..telling me the format was not recognized. On the site, i'm informed that the sound files include the following variants of .wav.. PCM, Microsoft ADPCM, ACM, and MPEG-3. Does anyone know (1) How to determine which format each file is and (2) whic format it is that "works" or imports and which does not??
lin (linque)


Dave Hollinden
Audio Engineer
Jet City Studios, Seattle
mailto:dhollindenatjetcitystudios [dot] com
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  FLASH: FLASH .wav files-not all equal?, linque

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