[alsa-devel] Noise in begnning of alsa application
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.
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
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
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.
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
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
participants (3)
-
Chakravarthi Pradeep -
Pavel Hofman -
Takashi Iwai