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aplay: try to use 16-bit format to increase capture quality
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Recently users reported a bug, I tested it and found it is a common
issue on Laptop or Desktop machines.

The issue is users plug a headset and use "arecord test.wav" to
record a sound with default input volume, the recorded sound has
poor quality and nearly can't distinguish it is the sound we want
to record.

This is because the input volume is low and the default format is U8.
The driver records sound with 16bit, because the input volume is low,
most of samples are within (-256,+256), when converting 16bit to U8,
those samples will be 0x7f. This is called quantization noise and we
could only workaround it by increase the input volume or adding -f to
arecord.

But users want to record a better quality sound with default input
volume (after installing a new OS, the volume is the default volume),
and they don't want to add parameters to the arecord because most of
new linux users just use "arecord test.wav".

So this patch tries to change the default format from U8 to S16_LE/BE.
If the machine doesn't support S16_LE/BE, it still uses U8 as default
format.

Signed-off-by: Hui Wang <hui.wang@canonical.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
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@jason77-wang @perexg
jason77-wang authored and perexg committed Oct 23, 2020
1 parent b2ae0b0 commit 0c5948e
Showing 1 changed file with 34 additions and 9 deletions.
43 changes: 34 additions & 9 deletions aplay/aplay.c
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@
#include <malloc.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <getopt.h>
#include <fcntl.h>
Expand Down Expand Up @@ -94,6 +95,7 @@ enum {
VUMETER_STEREO
};

static snd_pcm_format_t default_format = DEFAULT_FORMAT;
static char *command;
static snd_pcm_t *handle;
static struct {
Expand Down Expand Up @@ -468,6 +470,24 @@ static long parse_long(const char *str, int *err)
return val;
}

static void try_to_adjust_default_format_16bit(void)
{
snd_pcm_hw_params_t *params;
int err;

snd_pcm_hw_params_alloca(&params);
err = snd_pcm_hw_params_any(handle, params);
if (err < 0) {
error(_("Broken configuration for this PCM: no configurations available"));
prg_exit(EXIT_FAILURE);
}

if (file_type != FORMAT_AU && snd_pcm_hw_params_test_format(handle, params, SND_PCM_FORMAT_S16_LE) == 0)
rhwparams.format = default_format = SND_PCM_FORMAT_S16_LE;
else if (file_type == FORMAT_AU && snd_pcm_hw_params_test_format(handle, params, SND_PCM_FORMAT_S16_BE) == 0)
rhwparams.format = default_format = SND_PCM_FORMAT_S16_BE;
}

int main(int argc, char *argv[])
{
int duration_or_sample = 0;
Expand Down Expand Up @@ -528,6 +548,7 @@ int main(int argc, char *argv[])
int do_device_list = 0, do_pcm_list = 0;
snd_pcm_info_t *info;
FILE *direction;
bool user_set_fmt = false;

#ifdef ENABLE_NLS
setlocale(LC_ALL, "");
Expand Down Expand Up @@ -562,7 +583,7 @@ int main(int argc, char *argv[])
}

chunk_size = -1;
rhwparams.format = DEFAULT_FORMAT;
rhwparams.format = default_format;
rhwparams.rate = DEFAULT_SPEED;
rhwparams.channels = 1;

Expand Down Expand Up @@ -612,6 +633,7 @@ int main(int argc, char *argv[])
}
break;
case 'f':
user_set_fmt = true;
if (strcasecmp(optarg, "cd") == 0 || strcasecmp(optarg, "cdr") == 0) {
if (strcasecmp(optarg, "cdr") == 0)
rhwparams.format = SND_PCM_FORMAT_S16_BE;
Expand Down Expand Up @@ -844,6 +866,9 @@ int main(int argc, char *argv[])
}
}

if (!user_set_fmt)
try_to_adjust_default_format_16bit();

chunk_size = 1024;
hwparams = rhwparams;

Expand Down Expand Up @@ -1064,7 +1089,7 @@ static ssize_t test_wavefile(int fd, u_char *_buffer, size_t size)
hwparams.channels = channels;
switch (TO_CPU_SHORT(f->bit_p_spl, big_endian)) {
case 8:
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != SND_PCM_FORMAT_U8)
fprintf(stderr, _("Warning: format is changed to U8\n"));
hwparams.format = SND_PCM_FORMAT_U8;
Expand All @@ -1074,7 +1099,7 @@ static ssize_t test_wavefile(int fd, u_char *_buffer, size_t size)
native_format = SND_PCM_FORMAT_S16_BE;
else
native_format = SND_PCM_FORMAT_S16_LE;
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != native_format)
fprintf(stderr, _("Warning: format is changed to %s\n"),
snd_pcm_format_name(native_format));
Expand All @@ -1087,7 +1112,7 @@ static ssize_t test_wavefile(int fd, u_char *_buffer, size_t size)
native_format = SND_PCM_FORMAT_S24_3BE;
else
native_format = SND_PCM_FORMAT_S24_3LE;
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != native_format)
fprintf(stderr, _("Warning: format is changed to %s\n"),
snd_pcm_format_name(native_format));
Expand All @@ -1098,7 +1123,7 @@ static ssize_t test_wavefile(int fd, u_char *_buffer, size_t size)
native_format = SND_PCM_FORMAT_S24_BE;
else
native_format = SND_PCM_FORMAT_S24_LE;
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != native_format)
fprintf(stderr, _("Warning: format is changed to %s\n"),
snd_pcm_format_name(native_format));
Expand Down Expand Up @@ -1184,19 +1209,19 @@ static int test_au(int fd, void *buffer)
pbrec_count = BE_INT(ap->data_size);
switch (BE_INT(ap->encoding)) {
case AU_FMT_ULAW:
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != SND_PCM_FORMAT_MU_LAW)
fprintf(stderr, _("Warning: format is changed to MU_LAW\n"));
hwparams.format = SND_PCM_FORMAT_MU_LAW;
break;
case AU_FMT_LIN8:
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != SND_PCM_FORMAT_U8)
fprintf(stderr, _("Warning: format is changed to U8\n"));
hwparams.format = SND_PCM_FORMAT_U8;
break;
case AU_FMT_LIN16:
if (hwparams.format != DEFAULT_FORMAT &&
if (hwparams.format != default_format &&
hwparams.format != SND_PCM_FORMAT_S16_BE)
fprintf(stderr, _("Warning: format is changed to S16_BE\n"));
hwparams.format = SND_PCM_FORMAT_S16_BE;
Expand Down Expand Up @@ -2315,7 +2340,7 @@ static void voc_play(int fd, int ofs, char *name)
prg_exit(EXIT_FAILURE);
}
}
hwparams.format = DEFAULT_FORMAT;
hwparams.format = default_format;
hwparams.channels = 1;
hwparams.rate = DEFAULT_SPEED;
set_params();
Expand Down

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