[Freeswitch-users] .wav vs .gsm file sizes for recording calls.

[Steve Underwood]

Practically any conversion of a low bit rate codec to another low bit 
rate codec gives horrible results. Even low bit rate codec -> linear -> 
the same low bit rate codec can be pretty horrible, unless the two 
compression steps are synchronised.

A lot of the complaints you will find about the horrible sound from some 
codec has little to do with the codec's performance. Someone has tried 
the codec with audio that had already been compressed by some other low 
bit rate codec.

Steve

On 06/25/2011 05:53 AM, Jan Berger wrote:
>
> A gentle warning when using GSM codec’s
>
> Every codec compress voice at the cost of quality. And some codec’s 
> like GSM and G.729 are not a nice combination. If you use GSM to save 
> disk space and play it back using G.729 the resulting voice might 
> contain some added noise due to algorithmic incompatibility.
>
> jan
>
> ------------------------------------------------------------------------
>
> *From:*freeswitch-users-bounces at lists.freeswitch.org 
> [mailto:freeswitch-users-bounces at lists.freeswitch.org] *On Behalf Of 
> *David Ponzone
> *Sent:* 24. juni 2011 23:42
> *To:* FreeSWITCH Users Help
> *Subject:* Re: [Freeswitch-users] .wav vs .gsm file sizes for 
> recording calls.
>
> Wes,
>
> it's because you are confusing 2 things.
>
> GSM is a codec, so it's a sound format.
>
> WAVE is a kind of container (like MKV) that can contain various codecs.
>
> In your case, you probably did a mistake using sox (it's not an easy 
> tool), so you ended up with a wav which is still GSM audio inside.
>
> You have to tell sox which exact output format you want.
>
> AFAIR, you have to use the -s option (for signed linear).
>
> David Ponzone Direction Technique
>
> email: david.ponzone at ipeva.fr <mailto:david.ponzone at ipeva.fr>
>
> tel: 01 74 03 18 97
>
> gsm: 06 66 98 76 34
>
> Service ClientIPeva
>
> tel: 0811 46 26 26
>
> _www.ipeva.fr <BLOCKED::http://www.ipeva.fr/>_- _www.ipeva-studio.com 
> <BLOCKED::http://www.ipeva-studio.com/>_
>
> /Ce message et toutes les pièces jointes sont confidentiels et établis 
> à l'intention exclusive de ses destinataires. Toute utilisation ou 
> diffusion non autorisée est interdite. Tout message électronique est 
> susceptible d'altération. *IPeva* décline toute responsabilité au 
> titre de ce message s'il a été altéré, déformé ou falsifié. Si vous 
> n'êtes pas destinataire de ce message, merci de le détruire 
> immédiatement et d'avertir l'expéditeur./
>
> __
>
>
>
> Le 24/06/2011 à 23:26, Wes a écrit :
>
>
>
> In my tests, if I record a call in .wav format, a 10 second file is
> about 177,000 bytes, while a 10 second .gsm file is 17,000 bytes.
>
> I then used sox to convert the .gsm file to a .wav file, and it stayed
> at around 17,000 bytes. So, is the default recording format for .wav
> using a higher sample rate? vs the default conversion format for the sox
> tool?
>
> checking the file type using "file" I see that the larger one is:
> RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 8000 Hz
>
> and the wav created by sox via the default conversion from .gsm is:
> RIFF (little-endian) data, WAVE audio, GSM 6.10, mono 8000 Hz
>
> So apparently the larger wav file is 16 bit... how are these recording
> parameters controlled? Can I set it to record directly into the smaller
> wav format? Or will I have to run sox on every file...
>
> _______________________________________________
> Join us at ClueCon 2011, Aug 9-11, Chicago
> http://www.cluecon.com 877-7-4ACLUE
>
> FreeSWITCH-users mailing list
> FreeSWITCH-users at lists.freeswitch.org 
> <mailto:FreeSWITCH-users at lists.freeswitch.org>
> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
> http://www.freeswitch.org
>
>
> _______________________________________________
> Join us at ClueCon 2011, Aug 9-11, Chicago
> http://www.cluecon.com 877-7-4ACLUE
>
> FreeSWITCH-users mailing list
> FreeSWITCH-users at lists.freeswitch.org
> http://lists.freeswitch.org/mailman/listinfo/freeswitch-users
> UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users
> http://www.freeswitch.org