[PATCH] ALSA: ASoC: CS4270: export de-emphasis filter as ALSA control

[PATCH] ALSA: ASoC: CS4270: export de-emphasis filter as ALSA control

[Daniel Mack]

The CS4270 codec features an de-emphasis filter for compensation of
audio material filtered by an 50/15 uS algorithm. Not sure whether we
should always enable it for 44100Hz sampling frequency, but it should at
least be configurable by the user.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Timur Tabi <timur@freescale.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
---
 sound/soc/codecs/cs4270.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/sound/soc/codecs/cs4270.c b/sound/soc/codecs/cs4270.c
index ca1e24a..8069023 100644
--- a/sound/soc/codecs/cs4270.c
+++ b/sound/soc/codecs/cs4270.c
@@ -520,6 +520,7 @@ static const struct snd_kcontrol_new cs4270_snd_controls[] = {
 	SOC_SINGLE("Digital Sidetone Switch", CS4270_FORMAT, 5, 1, 0),
 	SOC_SINGLE("Soft Ramp Switch", CS4270_TRANS, 6, 1, 0),
 	SOC_SINGLE("Zero Cross Switch", CS4270_TRANS, 5, 1, 0),
+	SOC_SINGLE("De-emphasis filter", CS4270_TRANS, 0, 1, 0),
 	SOC_SINGLE("Popguard Switch", CS4270_MODE, 0, 1, 1),
 	SOC_SINGLE("Auto-Mute Switch", CS4270_MUTE, 5, 1, 0),
 	SOC_DOUBLE("Master Capture Switch", CS4270_MUTE, 3, 4, 1, 1),
-- 
1.6.5

Re: [PATCH] ALSA: ASoC: CS4270: export de-emphasis filter as ALSA control

[Timur Tabi]

Daniel Mack wrote:
> The CS4270 codec features an de-emphasis filter for compensation of
> audio material filtered by an 50/15 uS algorithm. Not sure whether we
> should always enable it for 44100Hz sampling frequency, but it should at
> least be configurable by the user.
>
> Signed-off-by: Daniel Mack<daniel@caiaq.de>
> Cc: Timur Tabi<timur@freescale.com>
> Cc: Mark Brown<broonie@opensource.wolfsonmicro.com>
> ---

Acked-by: Timur Tabi <timur@freescale.com>

Re: [PATCH] ALSA: ASoC: CS4270: export de-emphasis filter as ALSA control

[Mark Brown]

On Thu, Oct 29, 2009 at 02:24:32AM +0100, Daniel Mack wrote:
> The CS4270 codec features an de-emphasis filter for compensation of
> audio material filtered by an 50/15 uS algorithm. Not sure whether we
> should always enable it for 44100Hz sampling frequency, but it should at
> least be configurable by the user.

It shouldn't be automatically enabled - historically some sources put
some preemphasis on the recording in order to compensate for poor
playback technologies but it's vanishingly rare to encounter any such
sources these days.

I'll apply this.