Windows / C++ fread() stops reading in data from another process - c++

Question

So I've run into a quite frustrating problem... essentially I'm trying to transfer data between two different programs. The producer program sends data into stdout. The consumer program starts up the producer via _popen() and then uses fread() to read from that process... this works initially, but after maybe 15 loop iterations, the consumer starts reading in 0 bytes every time (even though the producer should still be outputting data).
I noticed if I tune the data-rates down a lot, I don't run into this problem... however that's not really an option, as in a real scenario, the data would be uncompressed video being piped in through ffmpeg.
Here is my consumer program:
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
int main() {
FILE * in = _popen("Pipe.exe", "r");
if(in == NULL){
printf("ERROR\n");
exit(0);
}
int stride = 163840;
char * buffer = (char*)malloc(stride);
int bytesRead;
while(true){
bytesRead = fread(buffer, 1, stride, in);
printf("%i\n", bytesRead);
Sleep(10);
}
}
And my producer program:
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
int main() {
int stride = 163840;
char * buffer = (char*) malloc(stride);
char value = 0;
while(true){
// This just changes the data for every loop iteration
for(int i = 0; i < stride; i++){
buffer[i] = value;
}
value = value == 255 ? 0 : value + 1;
fwrite(buffer, 1, stride, stdout);
Sleep(10);
}
}