[Freeswitch-users] echo cancelation

[Sergey Safarov]

According "Installing OSLEC with DAHDI" - DAHDI may use OSLEC. But I cant
find DAHDI requirements to compile and use OSLEC. In other words OSLEC may
be used without DAHDI.

On Sat, Apr 18, 2015 at 2:25 PM, Nandy Dagondon <nandy1925 at gmail.com> wrote:

>
> 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
>>>
>>>
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>>
>>
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>
>
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