[Freeswitch-users] echo cancelation

[Nandy Dagondon]

OSLEC works with FreeTDM DAHDI-mode.

On Sat, Apr 18, 2015 at 7:13 PM, Sergey Safarov <s.safarov at gmail.com> wrote:

> How would you expect to use echo cancellation in FS?
> I thinking it can be used like t38_gateway application (audio to image
> converter). In echo canceler application audio with echo converted to audio
> without echo.
>
> > On the one hand SpanDSP library compiled with FS and contains
> > functions for echo canceler libs/spandsp/src/echo.c
> Not really. Look carefully at those routines.
> In source
>  * echo.c - An echo cancellor, suitable for electrical and acoustic
>  *          cancellation. This code does not currently comply with
>  *          any relevant standards (e.g. G.164/5/7/8). One day....
> And other 70 string of following comments describe file as echo canceler
> Also in echo_can_update()
> at string 429
> clean_rx = rx - echo_value;
>
> at string 569
>     if ((ec->adaption_mode & ECHO_CAN_USE_NLP))
>     {
>         /* Non-linear processor - a fancy way to say "zap small signals,
> to avoid
>            residual echo due to (uLaw/ALaw) non-linearity in the
> channel.". */
>
> Look in echo.h comments ....
>
> in the echo_tests.c
> The echo cancellation tests test the echo cancellor against the G.168 spec.
>
> At http://www.rowetel.com/blog/?page_id=454 I read
> spandsp : A subset of spandsp to support testing and development of Oslec.
> The echo canceller and G168 test suite source code live in here.
>
> I thinking it really echo canceler functions.
>
> SpanDSP does NOT contain OSLEC. OSLEC has its origins in the work in
> progress echo canceller in SpanDSP.
> If it two different product then echo canceler may be realized by
>
>    1. SpanDSP library
>    2. Oslec kernel driver
>
> I has find relation In source files between OSLEC kernel driver
> (drivers/staging/echo) and SpanDSP functions:
> oslec_create(int len, int adaption_mode) - echo_can_init(int len, int
> adaption_mode)
> oslec_adaption_mode(struct oslec_state *ec, int adaption_mode) -
> oslec_update(struct oslec_state *ec, int16_t tx, int16_t rx)
> - echo_can_update(echo_can_state_t *ec, int16_t tx, int16_t rx)
> oslec_hpf_tx(struct oslec_state *ec, int16_t tx)
> - echo_can_hpf_tx(echo_can_state_t *ec, int16_t tx)
>
> And FS may use two echo canceler engines (SpanSDP or OSLEC kernel driver).
> What is prevent to do it?
>
>
>
>
>
>
>
> On Sat, Apr 18, 2015 at 12:39 PM, Steve Underwood <steveu at coppice.org>
> wrote:
>
>> On 04/18/2015 02:40 PM, Sergey Safarov wrote:
>> > Could you help me understand that prevents the use echo cancellation in
>> FS
>> How would you expect to use echo cancellation in FS?
>> > On the one hand SpanDSP library compiled with FS and contains
>> > functions for echo canceler libs/spandsp/src/echo.c
>> Not really. Look carefully at those routines.
>> > On the other hand FS does not contain applications of echo canceler.
>> Correct.
>> > Also, I found the discussion in which states GPL is not compatible
>> > with the MPL1.1 and it prevent use Oslec (SpanDSP is uses Oslec).
>> SpanDSP does NOT contain OSLEC. OSLEC has its origins in the work in
>> progress echo canceller in SpanDSP.
>>
>> Regards,
>> Steve
>>
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>>
>> Official FreeSWITCH Sites
>> http://www.freeswitch.org
>> http://confluence.freeswitch.org
>> http://www.cluecon.com
>>
>> 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
>>
>
>
> _________________________________________________________________________
> Professional FreeSWITCH Consulting Services:
> consulting at freeswitch.org
> http://www.freeswitchsolutions.com
>
> Official FreeSWITCH Sites
> http://www.freeswitch.org
> http://confluence.freeswitch.org
> http://www.cluecon.com
>
> 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
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.freeswitch.org/pipermail/freeswitch-users/attachments/20150418/762f7c3a/attachment.html