[Asterisk-Users] Low Volume WAV Files in Email Attachments

[Steven Critchfield]

On Sat, 2004-11-27 at 18:21 -0500, Gregory Junker wrote:
> I'm taking a look at the functions involved to see what the issue is, if 
> anyone cares.
> 
> One question tho....with all of the sound libraries on the planet, ones 
> that write to far mroe open formats, such as MP3, which are just as 
> acceptable as email attachments, and _have_ to be easier to deal with...

First, mp3 is patent encumbered. Also it seems most patent enforcement
is aimed at the encoders and not the decoders. Much like the way WMP and
Real work, those producing content can afford to pay for the work.

Second, read the rants on licensing. Unless you find a BSD licensed mp3
encoding library and convince Mark of it's need, it is unlikely to make
it to the core code base. 

Third, those complaining of low volume in emailed files are usually
using a compressed format. In the uncompressed wav format, the volume is
effectively doubled by shifting the audio data to the left one bit. This
is done at the format level. Of course on playback via asterisk, it
checks to see if it needs to shift the audio down and does so. So
playback between asterisk recorded wav files should all sound the same
on asterisk but isn't the same when played via a normal audio app.

I wouldn't mind seeing someone place a audio adjustment in the voicemail
app and make it adjustable. Then remove what I suspect is a crude hack
in format_wav.c

> But I digress....I'll dive in and snoop around format_wav_gsm anyway.

-- 
Steven Critchfield <critch at basesys.com>