This may be totally irrelevant and it may send you down the wrong track, but I
thought I would mention it:
There is a bug which can prevent recent versions of asterisk from creating
proper headers in WAV files.
The bug shows up on Solaris systems but Linux is theoretically not immune to it.
If you are creating raw ulaw or alaw files you should probably not expect any
headers when things are working normally.
But if you are creating wav files (which can contain alaw or ulaw data) and you
find a bunch of null characters (0x0) in the header, then you may have hit the
bug.
See: https://issues.asterisk.org/view.php?id=16610
> I did check content of two alaw files (using a hex editor) generated
> from two aboves cases. For the one fromo CentOS 5.2, beginning bytes
> look likes :
>
> RIFF1^0.WAVEfmt........ at ... at .......fact.....^0.data.^0...
>
> and the one from CentOS 5.5
>
> ......................RQVTV........XEMBAX............
>
> It seem like the first one have some information about file format,
> which make our convert tool works correctly, and which the second one
> doesnt have.