Noise in begnning of alsa application

Noise in begnning of alsa application

[Chakravarthi Pradeep]

I have ALSA driver for capture device which works fine with VLC. when
I try to capture and render using own application having some issues.
When I start play, it has some noise in beginning and audio is
discontinuous in between. Discontinuous means, some audio frame are
getting dropped in between. cut cut sound for sine wave. I have tried
snd_pcm_drop and snd_pcm_drain but no use. Kindly suggest how to
remove the starting noise in ALSA.

-- 
Thanks and Regards
Chakravarthi Pradeep.K

Re: Noise in begnning of alsa application

[Chakravarthi Pradeep]

Update from my side, for audio rendering i'm using below application.
I'm sharing reference render application which my own application is
built.

https://github.com/bear24rw/alsa-utils/blob/master/aplay/aplay.c

regards,
Chakravarthi Pradeep K

On Wed, Jan 16, 2019 at 5:07 PM Chakravarthi Pradeep <doubleq7@gmail.com> wrote:
>
> I have ALSA driver for capture device which works fine with VLC. when
> I try to capture and render using own application having some issues.
> When I start play, it has some noise in beginning and audio is
> discontinuous in between. Discontinuous means, some audio frame are
> getting dropped in between. cut cut sound for sine wave. I have tried
> snd_pcm_drop and snd_pcm_drain but no use. Kindly suggest how to
> remove the starting noise in ALSA.
>
> --
> Thanks and Regards
> Chakravarthi Pradeep.K



-- 
Thanks and Regards
Chakravarthi Pradeep.K
Ph: 91 9980434900

Re: Noise in begnning of alsa application

[Chakravarthi Pradeep]

On Wed, Jan 16, 2019 at 5:07 PM Chakravarthi Pradeep <doubleq7@gmail.com> wrote:
>
> I have ALSA driver for capture device which works fine with VLC. when
> I try to capture and render using own application having some issues.
> When I start play, it has some noise in beginning and audio is
> discontinuous in between. Discontinuous means, some audio frame are
> getting dropped in between. cut cut sound for sine wave. I have tried
> snd_pcm_drop and snd_pcm_drain but no use. Kindly suggest how to
> remove the starting noise in ALSA.
>
> For audio rendering i'm using below application.
> I'm sharing reference render application which my own application is
> built.

> https://github.com/bear24rw/alsa-utils/blob/master/aplay/aplay.c

-- 
Thanks and Regards
Chakravarthi Pradeep.K

Re: Noise in begnning of alsa application

[Pavel Hofman]

Dne 21. 01. 19 v 18:46 Chakravarthi Pradeep napsal(a):
> On Wed, Jan 16, 2019 at 5:07 PM Chakravarthi Pradeep <doubleq7@gmail.com> wrote:
>>
>> I have ALSA driver for capture device which works fine with VLC. when
>> I try to capture and render using own application having some issues.
>> When I start play, it has some noise in beginning and audio is
>> discontinuous in between. Discontinuous means, some audio frame are
>> getting dropped in between. cut cut sound for sine wave. I have tried
>> snd_pcm_drop and snd_pcm_drain but no use. Kindly suggest how to
>> remove the starting noise in ALSA.

I have experienced the same issue, with ice172 driver. IMO part of the 
first period when opening the stream contains samples from the previous 
run. In one of my my projects I have to drop initial samples in order to 
get correct and stable results from FFT analysis.

I do not know if the problem is in the driver, alsa-lib or if the 
application (in my case the SDL library) uses alsa-lib API incorrectly. 
To tell the truth I did not investigate details and "fixed" it by 
dropping the initial samples.

Best regards,

Pavel.

Re: Noise in begnning of alsa application

[Takashi Iwai]

On Mon, 21 Jan 2019 19:07:09 +0100,
Pavel Hofman wrote:
> 
> 
> Dne 21. 01. 19 v 18:46 Chakravarthi Pradeep napsal(a):
> > On Wed, Jan 16, 2019 at 5:07 PM Chakravarthi Pradeep <doubleq7@gmail.com> wrote:
> >>
> >> I have ALSA driver for capture device which works fine with VLC. when
> >> I try to capture and render using own application having some issues.
> >> When I start play, it has some noise in beginning and audio is
> >> discontinuous in between. Discontinuous means, some audio frame are
> >> getting dropped in between. cut cut sound for sine wave. I have tried
> >> snd_pcm_drop and snd_pcm_drain but no use. Kindly suggest how to
> >> remove the starting noise in ALSA.
> 
> I have experienced the same issue, with ice172 driver. IMO part of the
> first period when opening the stream contains samples from the
> previous run. In one of my my projects I have to drop initial samples
> in order to get correct and stable results from FFT analysis.
> 
> I do not know if the problem is in the driver, alsa-lib or if the
> application (in my case the SDL library) uses alsa-lib API
> incorrectly. To tell the truth I did not investigate details and
> "fixed" it by dropping the initial samples.

It's likely a driver-specific problem, but still wondering how it
happens.  Does the whole first period contain the previous samples, or
just a few beginning samples?

Also is it on the x86 PC, or on other architecture?


thanks,

Takashi

Re: Noise in begnning of alsa application

[Takashi Iwai]

On Mon, 21 Jan 2019 18:46:44 +0100,
Chakravarthi Pradeep wrote:
> 
> On Wed, Jan 16, 2019 at 5:07 PM Chakravarthi Pradeep <doubleq7@gmail.com> wrote:
> >
> > I have ALSA driver for capture device which works fine with VLC. when
> > I try to capture and render using own application having some issues.
> > When I start play, it has some noise in beginning and audio is
> > discontinuous in between. Discontinuous means, some audio frame are
> > getting dropped in between. cut cut sound for sine wave. I have tried
> > snd_pcm_drop and snd_pcm_drain but no use. Kindly suggest how to
> > remove the starting noise in ALSA.
> >
> > For audio rendering i'm using below application.
> > I'm sharing reference render application which my own application is
> > built.
> 
> > https://github.com/bear24rw/alsa-utils/blob/master/aplay/aplay.c

Such behavior is strongly depending on the hardware and the driver
code, so it's almost impossible to debug without the detailed hardware
and kernel information...


thanks,

Takashi