[Freeswitch-users] New features needed when playing files - playback application

[Steven Ayre]

What you're after is 'audio timescale pitch modification', aka
'time-stretching'.

It's a bit more specialised than a normal playback, so I suspect would
better implemented in a new application/module.

There's a few OSS libraries that might be of use. From a quick Google:
http://www.surina.net/soundtouch/ (LGPL)
http://breakfastquay.com/rubberband/ (GPL)

-Steve



On 21 March 2013 09:38, Clive Lansink <clive at lansink.co.nz> wrote:

>
> There are two features I need in the playback application for playing
> sound files for an IVR application I am developing. Maybe one feature is
> there but I don't think the other is but perhaps people could advise me
> about that.
>
> 1. I need to be able to start at a specified time offset in the file. When
> playing is interrupted, there is a variable that can tell the number of
> milliseconds of audio that was played. If I want to resume playing, I need
> to be able to start from that point, or in fact any arbitrary point, in the
> file. I think I can achieve this with the uuid_fileman API command so maybe
> that will work. When I last looked at this I was confused as to whether the
> seek parameter was samples or milliseconds.
>
> 2. I want to be able to vary the speed of playback but in such a way as to
> keep the overall pitch of the recorded voice unchanged. There are
> algorithms that do this and I presume they work by removing samples from or
> adding samples into the audio stream. I think uuid_fileman also has a speed
> subcommand which kind of worked when I played with it, but it was not
> constant pitch.
>
> The application I am working on is a replacement of a system that delivers
> human narrated information to blind people over the phone. The existing
> system uses old analogue Dialogic cards and has these features, and the
> replacement system should also have these capabilities. Recorded bulletins
> of information can be quite lengthy, maybe an hour or more to read right
> through. So this is perhaps not typical of IVR systems. People need to be
> able to skip around and possibly speed up or slow down the reading, but
> without altering the pitch of the narrator's voice. I know I can create the
> necessary functionality if I have the above features in the playback
> application.
>
> Note that the application will also use TTS to turn textual information
> into speech but that is a separate issue and not relevant here. The
> application still needs to handle human narrated information.
>
> Can anyone comment on these features and, if something needs to be added,
> how easy it would be to do this and how it might be done?
>
> Thank you.
>
>
> Clive Lansink
> Email: Clive at Lansink.Co.NZ
> Phone: +64 9 520-4242
> Mobile: +64 21 663-999
> Fax: +64 21 789-150
>
>
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