audiomixer implementation for audio conference , cancel user[1] contribution when streaming to user[1]

[Althaf K Backer]

This architecture is such that, we stream back  the audio participants
audio contribution via mixing them, to each of them negating their own
contribution. Issue is not about muting the participant, yes it can be
done that way, however, for such an implementation, we need n-adders
for n-users,
and so for n-th user's adder , we will not insert their audio
contribution. This method is an inefficient one, for a large group of
clients, say 1000+, and not to mention Linux has limit on number of
threads a process can have.

user-1]-[audio]-[tee0]
user-2]-[audio]-[tee1]
user-3]-[audio]-[tee2]
-------------------------------
  [tee2(src0)]->
                       [user-1-adder]->
  [tee3](src0]->
-------------------------------
  [tee1(src0)]->
                       [user-2-adder]->
  [tee3](src1]->
-------------------------------
  [tee1(src1)]->
                       [user-3-adder]->
  [tee2](src1]->
------------------------------
^^^This method is inefficient, which number of users grow.

The method that i propose, has a a Master-adder, which sums up all the
audio contribution, and each user has a adder + invert, which is as i
under stand is much less resource consuming than the former. Yes i do
see your point about the timing. I'm still rethinking new design for
this.

On Tue, May 21, 2013 at 11:44 PM, Chuck Crisler <ccrisler at mutualink.net> wrote:
> This is not an easy problem to solve. Your solution assumes that there isn't
> any delay, so you can invert the sample fast enough. But, if you can
> identify the participant's input, why not simply mute that input?
>
>
> On Sun, May 5, 2013 at 3:26 AM, Althaf K Backer
> <k.althaf at ais.aliftech.co.in> wrote:
>>
>> Below is the 'theoretical' pipeline that would cancel of particular
>> user's audio contribution in an audio conference mixer. Theory goes
>> like, we invert the user's audio samples from the original and it
>> finallyadded to the amixer output. It should cancel off. However i
>> can't figure of why i doesn't work in the pipeline below. The idea of
>> the mixer is that it sums of all the user's audio contribution and
>> when streaming back to individual user, their contribution is canceled
>> of with an 'invert' + 'addder' elements.
>>
>> I suspect clocking. or is it because these pipelines are separate ie
>> not in the single pipeline ?
>>
>> Readable representation of pipeline
>>
>> gst-launch
>> audiotestsrc name="sinewave" wave=sine ! tee name="audio_in_user1"
>> audio_in_user1. ! queue ! audioconvert ! amixer.sink0
>> audiotestsrc wave=ticks ! queue ! audioconvert !  amixer.sink2
>> adder name="amixer" ! tee name="mixerout"
>> mixerout. ! queue ! audio_out_user1.sink1
>> audio_in_user1. ! queue ! audioinvert degree=1 ! audioconvert !
>> audio_out_user1.sink1
>> adder name="audio_out_user1" ! alsasink
>>
>> Copy paste execute representation
>>
>> gst-launch audiotestsrc name="sinewave" wave=sine ! tee
>> name="audio_in_user1"  audio_in_user1. ! queue ! audioconvert !
>> amixer.sink0  audiotestsrc wave=ticks ! queue ! audioconvert !
>> amixer.sink2  adder name="amixer" ! tee name="mixerout"  mixerout. !
>> queue ! audio_out_user1.sink1  audio_in_user1. ! queue ! audioinvert
>> degree=1 ! audioconvert ! audio_out_user1.sink1  adder
>> name="audio_out_user1" ! alsasink
>>
>> A sample pipeline that works from above theory, pipeline has only one
>> audio source and it is cancelled in the adder.
>>
>> audioinvert degree=1
>>
>> gst-launch audiotestsrc name="sinewave" wave=sine ! tee
>> name="audiosource"  audiosource. ! queue ! audioconvert ! adder.sink0
>> audiosource. ! queue ! audioinvert degree=1 ! audioconvert !
>> adder.sink1   adder name="adder" ! alsasink
>>
>>
>> audioinvert degree=1
>>
>> gst-launch audiotestsrc name="sinewave" wave=sine ! tee
>> name="audiosource"  audiosource. ! queue ! audioconvert ! adder.sink0
>> audiosource. ! queue ! audioinvert degree=0.55 ! audioconvert !
>> adder.sink1   adder name="adder" ! alsasink
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>
>
>
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