[asterisk-users] Re: Choice of soundfile format

[Martin Joseph]

On 2006-10-25 22:33:47 -0700, John Marvin <jm-asterisk at themarvins.org> said:

> Martin Joseph wrote:
> 
>> Transcoding is a bigger hit then mixing as i understand it.
>> 
>> If all the conference members are using ulaw for example, then having 
>> the playback material encoded in ulaw is the big winner.  If there are 
>> different codecs connecting, then there is a lot of 
>> decoding/mixing/recoding that will need to occur.
> 
> There is a misunderstanding here. The only time transcoding is not 
> required is when data is just being "passed through", either from a 
> data file (recording, Music on Hold, Voicemail, etc.) or from one 
> channel to another, AND the format is the same.
> 
> However, once mixing is required, i.e. for a conference, transcoding 
> will always be required because you can't mix compressed data. All 
> channels have to be decoded to sLinear, mixed, and then reencoded.


Thanks for clearing that up John.  My mistake in somehow thinking if 
all channels where ulaw they could be mixed without transcoding...  
Sorry for any confusion.

Marty