[alsa-devel] Question about Conversion to S24_LE from S24_3LE

[Tan, Seng Kai]

Hi Takashi,

I am facing similar problem like this issue, hope to get your advice.
http://mailman.alsa-project.org/pipermail/alsa-devel/2012-August/054241.html

I try to turn on S24_LE support for HDMI Audio using below patch. When I aplay S24_LE file it works fine.
The problem happen when I aplay S24_3LE file, I get and extremely low volume.

When I aplay S24_LE file, I get an left justified value in I2S, this is an expected result:
Front end S24_LE  :  0x12345600(in 4bytes, LSB 0 padding)
Back end  S24_3LE :  0x12345600(in 4bytes, LSB 0 padding)

When I aplay S24_3LE file, I get an extremely low output volume. 
Front end S24_3LE  :  0x123456(in 3bytes, No padding)
Back end  S24_LE :  0x00123456(in 4bytes, MSB 0 padding)

Can you advice how to tell the alsa plugin to pad in LSB instead of MSB?

Below are the patch I used to turn on S24_LE for HDA .

Regards,
Seng Kai




>From 33f182fe1f6d1e49d0618559d1212b619ec902ce Mon Sep 17 00:00:00 2001
From: "SengKai,Tan" <seng.kai.tan at intel.com>
Date: Fri, 8 Apr 2016 17:34:51 +0800
Subject: [PATCH] ALSA: hda: S24_LE format support for HDA Audio

This patch is to add S24_LE support for  HDMI audio
and HDA codec.

Before this patch, HDMI and HDA codec audio only
supported S16_LE and S32_LE. Let's say if user would
like to play S24_LE file, it has to use plugin to
convert to either S16_LE or S32_LE which will
increase in processing and less efficient in utilize
the resources.

On the other side, let's say connected HDMI monitor
support S16_LE and S24_LE. Before this patch is applied
audio has to be converted to S16_LE. That will reduce
the audio quality.

Signed-off-by: Tan, Seng Kai <seng.kai.tan at intel.com>
---
 sound/pci/hda/hda_codec.c  | 6 ++++--
 sound/pci/hda/hda_eld.c    | 6 ++++--
 sound/pci/hda/patch_hdmi.c | 3 ++-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/sound/pci/hda/hda_codec.c b/sound/pci/hda/hda_codec.c
index 57197be..9e737bb 100644
--- a/sound/pci/hda/hda_codec.c
+++ b/sound/pci/hda/hda_codec.c
@@ -3501,14 +3501,16 @@ int snd_hda_query_supported_pcm(struct hda_codec *codec, hda_nid_t nid,
 				if (val & AC_SUPPCM_BITS_32)
 					formats |= SNDRV_PCM_FMTBIT_IEC958_SUBFRAME_LE;
 				if (val & (AC_SUPPCM_BITS_20|AC_SUPPCM_BITS_24))
-					formats |= SNDRV_PCM_FMTBIT_S32_LE;
+					formats |= SNDRV_PCM_FMTBIT_S24_LE |
+						SNDRV_PCM_FMTBIT_S32_LE;
 				if (val & AC_SUPPCM_BITS_24)
 					bps = 24;
 				else if (val & AC_SUPPCM_BITS_20)
 					bps = 20;
 			} else if (val & (AC_SUPPCM_BITS_20|AC_SUPPCM_BITS_24|
 					  AC_SUPPCM_BITS_32)) {
-				formats |= SNDRV_PCM_FMTBIT_S32_LE;
+				formats |= SNDRV_PCM_FMTBIT_S24_LE |
+					SNDRV_PCM_FMTBIT_S32_LE;
 				if (val & AC_SUPPCM_BITS_32)
 					bps = 32;
 				else if (val & AC_SUPPCM_BITS_24)
diff --git a/sound/pci/hda/hda_eld.c b/sound/pci/hda/hda_eld.c
index 0e6d753..65bfe10 100644
--- a/sound/pci/hda/hda_eld.c
+++ b/sound/pci/hda/hda_eld.c
@@ -613,12 +613,14 @@ void snd_hdmi_eld_update_pcm_info(struct parsed_hdmi_eld *e,
 			channels_max = a->channels;
 		if (a->format == AUDIO_CODING_TYPE_LPCM) {
 			if (a->sample_bits & AC_SUPPCM_BITS_20) {
-				formats |= SNDRV_PCM_FMTBIT_S32_LE;
+				formats |= SNDRV_PCM_FMTBIT_S24_LE |
+					SNDRV_PCM_FMTBIT_S32_LE;
 				if (maxbps < 20)
 					maxbps = 20;
 			}
 			if (a->sample_bits & AC_SUPPCM_BITS_24) {
-				formats |= SNDRV_PCM_FMTBIT_S32_LE;
+				formats |= SNDRV_PCM_FMTBIT_S24_LE |
+					SNDRV_PCM_FMTBIT_S32_LE;
 				if (maxbps < 24)
 					maxbps = 24;
 			}
diff --git a/sound/pci/hda/patch_hdmi.c b/sound/pci/hda/patch_hdmi.c
index d02eccd..8cbde13 100644
--- a/sound/pci/hda/patch_hdmi.c
+++ b/sound/pci/hda/patch_hdmi.c
@@ -2489,7 +2489,8 @@ static const struct hda_verb nvhdmi_basic_init_7x_8ch[] = {
 	 SNDRV_PCM_RATE_192000)
 #define SUPPORTED_MAXBPS	24
 #define SUPPORTED_FORMATS \
-	(SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S32_LE)
+	(SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S24_LE |\
+	SNDRV_PCM_FMTBIT_S32_LE)
 #endif
 
 static int nvhdmi_7x_init_2ch(struct hda_codec *codec)
-- 
1.9.1