[Speex-dev] CCITT A-Law to Speex conversion

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Tue Jul 29 19:50:44 PDT 2008

Goes something like:

sox -t ul -r 8000 -c 1 my_ulaw_file -t sw - | speexenc - my_speex_file

(warning, I haven't actually tested that, so there could be a typo)



Sander Bol a écrit :
> Hello group,
> I'm not sure this is the right place to ask a user-question instead of a
> dev-question - if not, a pointer in the proper direction would be
> appreciated.
> My issue is that I want to automatically (in a nightly batch job)
> convert a large number of voice recordings from A-Law WAV to Speex, in
> order to reduce storage and bandwidth demands for tranferring the files
> over our LAN. In my understanding, SpeexEnc can not handle A-Law
> directly (it tells me it can only handle PCM). Google has led me to
> believe SOX is an appropriate tool to first convert A-Law --> PCM, which
> can then be piped into SpeexEnc. Having found that, I've looked into
> SOX, but having no background in audio conversion I find myself slightly
> overwhelmed with the plethora of options and switches available. The
> attempts I've done so far, fiddling with different in-file and out-file
> settings, resulted in lots of clipping in the intermediate WAV file, and
> static noise (or the PCM error) when trying to convert the resulting
> file in Speex. Further Googling has yielded lots of shareware sites
> offering GUI-based tools that can convert between a myriad of formats,
> but have not resulted in any relevant hits.
> Is SOX indeed the proper tool to use, and if so, what switches do I need
> in order to convert these files to a format Speex can handle with as
> little pre-Speex loss as possible?
> Thanks for your time,
> Sander Bol
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