[alsa-devel] Pop and offsets at start of audio playback/record for SGTL5000 on i.MX28

[Michael Trimarchi]

Hi

Il 14/nov/2014 09:44 "Craig McQueen" <craig.mcqueen at beamcommunications.com>
ha scritto:
>
> I'm testing the 3.14.19 kernel for i.MX28 EVK, which has an SGTL5000
CODEC. I've also tested on the 3.18-rc4 kernel and confirmed this issue
still occurs.
>

Are you using it in master or slave mode?

Michael

>
> Playback
>
> When doing audio playback, I notice that the audio "fades in" over the
first (approximately) 500 ms of playback. This is very noticeable and not
ideal in certain applications (e.g. audio notifications that are of short
duration).
>
> However, if audio playback starts while audio recording is already
in-progress, then there is no fade-in; instead there is a loud pop. I
assume the fade-in is there to mask the pop. The pop is very unpleasant
through headphones. (However, if I do audio playback a _second_ time while
audio recording is still in-progress, then there is no loud pop the second
time.)
>
> I didn't think either the pop or the fade-in occurred on the 2.6.35
kernel. How feasible is it to improve the driver to avoid or reduce the
pop, and remove the necessity for a fade-in?
>
>
> Record
>
> When recording, I notice there is a low-frequency ramping offset at the
start of a recording (after the 400-500 ms of previous audio) of approx
600-700 ms duration. This also reduces the audio quality at the start of
the recording. It could reduce the quality of captured audio depending on
the application usage. I am getting distortion (clipping I assume) of my
audio input during this time. It could cause a pop on playback (local
playback or e.g. VoIP transmission to a remote device). It could reduce the
audio quality through an audio CODEC.
>
> How feasible is it to improve the driver to avoid a ramping offset at the
start of recording?
>
> --
> Craig McQueen
>
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel at alsa-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel