[Freeswitch-users] Playing multiple files simultaneously

[Bryan Smart]

Thanks for the warning, Steve.

The cues are short, and I'm trying to keep them thin (simple waveforms based on multifrequency sine waves for tone, and short filtered white noise where clicks or percussive transients are required). I'm not an expert on low bit rate audio, but, from the bit that I know, I think that simple audio cues like this will mix better than sampled musical instruments playing riffs, real world sounds, and so on. Sounds alright on GSM, but I haven't tested with G729 yet. Do you think this will work for me?

I'm not actually planning an overlapping cacophony of sound. The cues are short, but I'd like them to be able to play in the background while text to speech or a recorded prompt is playing. I don't anticipate lots of them playing at once, but I wanted the mixing capability so that they could play under the speech, and so that, when two play close in a row, the second one wouldn't chop off the end of the first.

Do you know if it is better to try to extend existing commands, like playback, or if it would be better to have a separate module and commands for playing audio in this way? I realize that mixing would introduce at least a small overhead, even if all files and the channel were same format, and most people would want to avoid that little performance hit unless they specifically needed the mixing capability.

I feel cautious about poking my nose in to programming issues here. I've been programming to one degree or another for 25 years, and even had it as my main gig for several years, but all of my experience has either been personal projects, or closed source commercial development for an employer. I don't have my head around people and technical processes for contributing to an open source project, so even tweaking a single line in a source file seems to involve a lot of process in order to submit it. I know that the group uses git for version control, but, if I make a tweak, do I submit it to some sort of approval branch first? If their is a processes doc for the group, I'd be glad to read it.

Thanks
Bryan

On Jul 6, 2011, at 9:11 PM, Steve Underwood wrote:

> On 07/01/2011 01:13 PM, Bryan Smart wrote:
>> Is it possible for Freeswitch to play more than one file to a channel at a time? What I've seen and tried from the dialplan and scripts either queues files to play, or will stop a currently playing file so that the newly requested file will play. This also seems to be the case in conferences. When I send multiple play commands to conferences, the files are queued.
>> 
>> As for how this might be used, think of an IVR that plays queued prompts, yet continuously plays looping music or a Shoutcast stream in the background. I also want to be able to play short cue tones that start at the same time as a prompt (don't want to pre-mix them in to a single file, though).
>> 
>> Is this currently possible through any means? Perhaps with the event socket?
>> 
> Be really careful making plans like this. Multiple sounds will mix 
> nicely with something like ALaw or uLaw. If you try it with a low bit 
> rate codec, like G.729 or a cellphone codec, the result will sound 
> awful. Modern telephony really is geared to one voice and one voice only 
> at any moment.
> 
> Steve
> 
> 
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