ImageMagick book
MythTV book
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Mon, 09 Sep 2002
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I am currently having some pain reading very small amounts of input from stdin with bash. For example I want to be able to just pull the next byte of stdin (as a string). read wants to pull lines.
I did think of doing something like:
cat - > /tmp/foo
cat /tmp/foo | cut -b 42
But the problem with this is that stdin of the bash script I am writing never ends. Perhaps I could so something like:
cat - > /tmp/foo &
cat /tmp/foo | cut -b 42
Then I need to be able to handle the scenario when the reader is ahead of the writing, probably by just spinning until the input appears.
This of course doesn't work as I had expected it to, because the first cat can't be backgrounded because then it looses access to stdin. I need some sort of forking mechanism...
posted at: 00:00 | path: /problemcode | permanent link to this entry
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Mon, 01 Apr 2002
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It turns out the problem is that I needed to byte swap the audio data from the wav file before playing it. The fixed code looks like:
// Routines to handle the sound for Vic, the Bug
#include
#include
#include
#include
#include
#include
#include
#include
int slots[100];
unsigned int toInteger(char *in){
unsigned int ret;
int i;
char *p = ((char *) &ret);
for(i = 0; i < 4; i++){
*p++ = in[i];
}
return ret;
}
char *getBytes(int input, size_t number, char *expect){
char *data;
int i;
ssize_t numRead;
if((data = malloc(number + 1)) == NULL){
fprintf(stderr, "Malloc error\n");
exit(0);
}
if((numRead = read(input, data, number)) < 1){
fprintf(stderr, "Malformed wav file (EOF)\n");
exit(0);
}
data[numRead] = 0;
if(expect != NULL){
for(i = 0; i < numRead; i++)
data[i] = tolower(data[i]);
if(strcmp(expect, data) != 0){
fprintf(stderr, "Read \"");
for(i = 0; i < numRead; i++)
fprintf(stderr, "%c", (isprint(data[i])) ? data[i] : '%');
fprintf(stderr, "\", expected \"%s\"\n", expect);
}
}
return data;
}
void playSound(int slotNumber, char *filename){
slots[slotNumber] = 0;
switch(fork()){
case -1:
// Parent with failure
fprintf(stderr, "Sound play fork error\n");
return;
break;
case 0:
// Child
{
int soundHandle = -1, fileHandle = -1;
int channels = 1; // stereo
int format;
unsigned int rate = 22050;
unsigned int fmtLen;
int bytes = 0;
long i;
char *data, *data2;
char *tempPtr;
ssize_t numRead;
printf("Play sound %s\n", filename);
if((fileHandle = open(filename, O_RDONLY)) == -1){
fprintf(stderr, "Could not open the specified wav file: %s\n",
filename);
exit(0);
}
// Check the format of the wav file
free(getBytes(fileHandle, 4, "riff"));
free(getBytes(fileHandle, 4, NULL)); // Length of package
free(getBytes(fileHandle, 4, "wave"));
free(getBytes(fileHandle, 4, "fmt "));
tempPtr = getBytes(fileHandle, 4, NULL);
fmtLen = toInteger(tempPtr);
free(tempPtr);
free(getBytes(fileHandle, 2, NULL)); // Reserved
tempPtr = getBytes(fileHandle, 2, NULL);
channels = tempPtr[0] - 1;
free(tempPtr);
tempPtr = getBytes(fileHandle, 4, NULL);
rate = toInteger(tempPtr);
free(tempPtr);
free(getBytes(fileHandle, 4, NULL)); // Bytes per second
tempPtr = getBytes(fileHandle, 2, NULL);
bytes = tempPtr[0];
free(tempPtr);
free(getBytes(fileHandle, 2, NULL)); // Bits per sample
free(getBytes(fileHandle, 4, "data"));
free(getBytes(fileHandle, 3, NULL)); // Length of data
// Open the sound interface
if((soundHandle = open("/dev/dsp", O_WRONLY)) == -1){
fprintf(stderr, "Couldn't open the sound device\n");
exit(0);
}
if(ioctl(soundHandle, SNDCTL_DSP_STEREO, &channels) == -1){
fprintf(stderr, "Could not set stereo\n");
exit(0);
}
else{
printf("\nStereo set to %d\n", channels);
}
switch(bytes){
case 1:
format = AFMT_U8;
break;
case 2:
if(channels == 0)
format = AFMT_S16_LE;
else
format = AFMT_U8;
break;
case 4:
fprintf(stdout, "Stereo wav file\n");
format = AFMT_S16_LE;
break;
default:
fprintf(stderr, "Unknown byte rate for sound\n");
exit(0);
}
if(ioctl(soundHandle, SNDCTL_DSP_SETFMT, &format) == -1){
fprintf(stderr, "Could not set format\n");
exit(0);
}
else{
printf("Format set to %d\n", format);
}
if(ioctl(soundHandle, SNDCTL_DSP_SPEED, &rate) == -1){
fprintf(stderr, "Could not set rate\n");
exit(0);
}
else{
printf("Speed set to %d\n", rate);
}
fprintf(stdout,
"Playing file %s: channels = %d, rate = %d, bytes = %d\n",
filename, channels, rate, bytes);
if((data2 = malloc(1024)) == NULL){
fprintf(stderr, "Memory allocation error\n");
exit(0);
}
while(1){
if((numRead = read(fileHandle, data, 1024)) == 0)
break;
for(i = 0; i < numRead; i+=2){
data2[i] = data[i+1];
data2[i+1] = data[i];
}
if(write(soundHandle, data2, numRead) == -1){
fprintf(stderr, "Error writing to the sound device\n");
exit(0);
}
}
// Get here when done?
close(fileHandle);
close(soundHandle);
free(data);
exit(0);
}
break;
default:
return;
break;
}
}
posted at: 00:00 | path: /problemcode | permanent link to this entry
There are no comments on this post which have survived moderation. 67 posts have been culled and 129 blocked. Be the first to make a non-spam comment here, please!
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Fri, 29 Mar 2002
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// Routines to handle the sound for Vic, the Bug
#include
#include
#include
#include
#include
#include
#include
#include
int slots[100];
unsigned int toInteger(char *in){
unsigned int ret;
int i;
char *p = ((char *) &ret);
for(i = 0; i < 4; i++){
*p++ = in[i];
}
return ret;
}
char *getBytes(int input, size_t number, char *expect){
char *data;
int i;
ssize_t numRead;
if((data = malloc(number + 1)) == NULL){
fprintf(stderr, "Malloc error\n");
exit(0);
}
if((numRead = read(input, data, number)) < 1){
fprintf(stderr, "Malformed wav file (EOF)\n");
exit(0);
}
data[numRead] = 0;
fprintf(stdout, "[%d] ", numRead);
fflush(stdout);
if(expect != NULL){
for(i = 0; i < numRead; i++)
data[i] = tolower(data[i]);
if(strcmp(expect, data) != 0){
fprintf(stderr, "Read \"");
for(i = 0; i < numRead; i++)
fprintf(stderr, "%c", (isprint(data[i])) ? data[i] : '%');
fprintf(stderr, "\", expected \"%s\"\n", expect);
}
}
return data;
}
void playSound(int slotNumber, char *filename){
slots[slotNumber] = 0;
switch(fork()){
case -1:
// Parent with failure
fprintf(stderr, "Sound play fork error\n");
return;
break;
case 0:
// Child
{
int soundHandle = -1, fileHandle = -1;
int channels = 1; // stereo
int format;
unsigned int rate = 22050;
unsigned int fmtLen;
int bytes = 0;
long i;
char *data;
char *tempPtr;
ssize_t numRead;
if((fileHandle = open(filename, O_RDONLY)) == -1){
fprintf(stderr, "Could not open the specified wav file: %s\n",
filename);
exit(0);
}
// Check the format of the wav file
free(getBytes(fileHandle, 4, "riff"));
free(getBytes(fileHandle, 4, NULL)); // Length of package
free(getBytes(fileHandle, 4, "wave"));
free(getBytes(fileHandle, 4, "fmt "));
tempPtr = getBytes(fileHandle, 4, NULL);
fmtLen = toInteger(tempPtr);
free(tempPtr);
free(getBytes(fileHandle, 2, NULL)); // Reserved
tempPtr = getBytes(fileHandle, 2, NULL);
channels = tempPtr[0] - 1;
free(tempPtr);
tempPtr = getBytes(fileHandle, 4, NULL);
rate = toInteger(tempPtr);
free(tempPtr);
free(getBytes(fileHandle, 4, NULL)); // Bytes per second
tempPtr = getBytes(fileHandle, 2, NULL);
bytes = tempPtr[0];
free(tempPtr);
free(getBytes(fileHandle, 2, NULL)); // Bits per sample
free(getBytes(fileHandle, 4, "data"));
free(getBytes(fileHandle, 3, NULL)); // Length of data
// Open the sound interface
if((soundHandle = open("/dev/dsp", O_WRONLY)) == -1){
fprintf(stderr, "Couldn't open the sound device\n");
exit(0);
}
if(ioctl(soundHandle, SNDCTL_DSP_STEREO, &channels) == -1){
fprintf(stderr, "Could not set stereo\n");
exit(0);
}
switch(bytes){
case 1:
format = AFMT_U8;
break;
case 2:
if(channels == 0)
format = AFMT_S16_LE;
else
format = AFMT_U8;
break;
case 4:
fprintf(stdout, "Stereo wav file\n");
format = AFMT_S16_LE;
break;
default:
fprintf(stderr, "Unknown byte rate for sound\n");
exit(0);
}
if(ioctl(soundHandle, SNDCTL_DSP_SETFMT, &format) == -1){
fprintf(stderr, "Could not set format\n");
exit(0);
}
if(ioctl(soundHandle, SNDCTL_DSP_SPEED, &rate) == -1){
fprintf(stderr, "Could not set rate\n");
exit(0);
}
fprintf(stdout,
"Playing file %s: channels = %d, rate = %d, bytes = %d\n",
filename, channels, rate, bytes);
while(1){
if((numRead = read(fileHandle, data, 1024)) == 0)
break;
fprintf(stdout, "[%d] ", numRead);
fflush(stdout);
if(write(soundHandle, data, numRead) == -1){
fprintf(stderr, "Error writing to the sound device\n");
exit(0);
}
if(ioctl(soundHandle, SNDCTL_DSP_SYNC) == -1){
fprintf(stderr, "Could not sync sound data\n");
exit(0);
}
// free(data);
}
// Get here when done?
close(fileHandle);
close(soundHandle);
free(data);
exit(0);
}
break;
default:
return;
break;
}
}
posted at: 22:00 | path: /problemcode | permanent link to this entry
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The following code works just fine with 8KHz mono sound, but has troubles with stereo 44KHz sound. The stereo wav files just come out as loud clicking noises. I imagine this is something simple with my IOCTL setup, but I can't see it...
posted at: 22:00 | path: /problemcode | permanent link to this entry
There are no comments on this post which have survived moderation. 94 posts have been culled and 126 blocked. Be the first to make a non-spam comment here, please!
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