Subject: Re: [linux-audio-dev] laptop sound
From: douglas irving repetto (douglas_AT_music.columbia.edu)
Date: Mon Nov 27 2000 - 22:10:03 EET
Paul Winkler wrote:
>
> The Diamond Sonic Impact based on this same chip was described as
> "near-CD quality in playback and near-telephone quality in recording".
> I think this is what I have in my laptop. Playback does sound pretty
> decent. Haven't tried recording yet.
>
speaking of bad-sounding laptops, the maestro 2e in my dell inspiron
7500 sounds really crappy with the passthru code below when i a/b a CD.
just playing the CD normally sounds fine, but i guess it must be using
another set of converters on the CD player itself. it's amazing how bad
one generation of d/a -> a/d -> d/a can sound! it's all noisey and buzzy
and sounds like it's being very subtly ring-modulated!
good thing this is my primary axe for live gigs...
douglas
/*
soundthru.c
*/
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <sys/soundcard.h>
#define BUFFER_SIZE 1024
#define FORMAT AFMT_S16_LE
#define CHANNELS 1 // 0=mono 1=stereo
#define SAMPLE_RATE 44100
int soundthru()
{
//file i/o
short* in_ptr;
short* in_data_start_ptr;
int bytes_read = 0;
int bytes_written = 0;
int handle;
int channels;
int format;
int sample_rate;
int setting;
short write_size;
handle = -1;
//format info
channels = CHANNELS;
format = FORMAT;
sample_rate = SAMPLE_RATE;
setting = 0x0003000C; // 3 fragments 4kb buffer
//1024 * 2 channels * 2 bytes per sample
write_size = BUFFER_SIZE * 2 * 2L;
if ( (handle = open("/dev/dsp",O_RDWR)) == -1 ) {
perror("open /dev/dsp");
return -1;
}
if ( ioctl(handle, SNDCTL_DSP_SETFRAGMENT, &setting) == -1 ) {
perror("ioctl set fragment");
return errno;
}
if ( ioctl(handle, SNDCTL_DSP_STEREO, &channels) == -1 ) {
perror("ioctl stereo");
return errno;
}
if ( ioctl(handle, SNDCTL_DSP_SETFMT, &format) == -1 ) {
perror("ioctl format");
return errno;
}
if ( ioctl(handle, SNDCTL_DSP_SPEED, &sample_rate) == -1 ) {
perror("ioctl sample rate");
return errno;
}
in_data_start_ptr = (short*)malloc(write_size);
memset(in_data_start_ptr, 0, write_size);
in_ptr = in_data_start_ptr;
while (1)
{
in_ptr = in_data_start_ptr;
//get input samples
bytes_read = read(handle, in_ptr, write_size);
if (bytes_read < 0)
{
printf("problem reading input. goodbye.\n");
return -1;
}
else if (bytes_read < write_size)
printf("read: %d of %d\n", bytes_read, write_size);
//write them back out
bytes_written = write(handle, in_ptr, write_size);
if (bytes_written < 0)
{
printf("problem writing output. goodbye.\n");
return -1;
}
else if (bytes_written < write_size)
printf("wrote: %d of %d\n", bytes_read, write_size);
}
return 0;
}
int main()
{
soundthru();
return 0;
}
--
douglas irving repetto
http://music.columbia.edu/~douglas
the music-dsp mailing list and website:
http://shoko.calarts.edu/musicdsp
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