Android phone as webcam to capture binary clock patterns

A while ago I got a binary clock for my birthday by some college friends (thank you again at this point). When you watch it from the sofa, you can sometimes see it creating some interesting or funny shapes and I wondered how many of them are there.

Sure, you could write a program to generate all combinations but I wanted to make a photo for each of the clock’s states. Since I don’t have a webcam or something more advanced – the idea was to use my android phone.

Searching for an app, I found this really great and easy one IP Webcam which allows you to take shots via HTTP or and directly grab an image from the video buffer. Luckily this was fast enough to make a picture every second. This was not the case when I tried using the auto focus and normal photo mode.

I wrote a little C program to print out seconds and microseconds to analyze the camera’s delay by taking a shot of the screen. The result surprised me a little since the picture was actually from before it was triggered and not after.
The explanation is at hand, the picture from the camera is buffered on the phone or the app and you simple get a snapshot of what is ready at that time.

I’ll just dump the source code of the program to take a shot every second here and with some interesting pictures I found after recording about ten hours. one to ten o’clock.

/* makeshots.c */

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <string.h>
#include <unistd.h>
#include <time.h>

#define MSSLEEP "./mssleep"
#define CAMERA_LATENCY "350000"
#define CAMERA_URL "\"http://192.168.1.112:8080/shot.jpg\""
// printf
#define TIMEFORMAT "%010ld,%06ld"
// strftime
#define OUTTIMEFORMAT "%H_%M_%S"

#define MINUTE 60l
#define HOUR (60l * MINUTE)
// 86_400 pictures per 24 hours
#define RUNTIME (10l * HOUR + MINUTE)
#define LOOPWAIT_MS 2000

void shoot() {
  char shoot_cmd[256];
  char timestamp[128];
  struct tm tmine;
  time_t rawtime;

  time (&rawtime);
  localtime_r(&rawtime, &tmine);

  strftime(timestamp, 128, OUTTIMEFORMAT, &tmine);
  snprintf(
    shoot_cmd,
    256,
    "("MSSLEEP" "CAMERA_LATENCY"; curl -s -S "CAMERA_URL" -o out/%s.jpg 2>> curl.log) &",
    timestamp
  );
  system(shoot_cmd); // returns immediately
}

int main(int argc, char **argv) {
  struct timeval t;
  struct timezone tz;

  // init
  if (gettimeofday(&t, &tz)) {
    perror("gettimeofday in init failed");
  }
  time_t start_sec = t.tv_sec;
  time_t lastsec   = t.tv_sec;

  while (t.tv_sec - start_sec < RUNTIME) {
    if (gettimeofday(&t, &tz)) {
      perror("gettimeofday in loop failed");
    }
    printf(TIMEFORMAT, (long) t.tv_sec, (long) t.tv_usec);

    // Shoot every second
    if (t.tv_sec - lastsec > 0) {
      lastsec = t.tv_sec;
      shoot();
    }

    usleep(LOOPWAIT_MS);
    // Must be as long as TIMEFORMAT
    printf("\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r\r");
  }
  printf("\n");
  return EXIT_SUCCESS;
}
/* mssleep.c */

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <string.h>
#include <unistd.h>

int main(int argc, char **argv) {
  if (argc != 2) {
    fprintf(stderr, "%s: <milliseconds>\n", argv[0]);
    return EXIT_FAILURE;
  }

  long ms = atol(argv[1]);
  usleep((useconds_t) ms);
  return EXIT_SUCCESS;
}

I was using C to get a good performance but mostly since it has been a while and I wanted to get my hands on it again. The code runs on mac osx leopard using gcc. curl must be installed.

Werbeanzeigen

Android music player shuffle is bad

I just wanted to share my experience with the android music player.
From a user interface and feature perspective I am totally happy with it. It is kind of simple, responsive and okay to control as music player in your car. (Hands free of course).

But there is a problem with the shuffle function. I use that feature a lot, since the android is serving me with music almost every day in my car and I really can’t stand the same playlist order every day. The sequential order makes things too predictable and you rapidly get the feeling you heard the songs a million times.

Unfortunately android music player is not shuffling very well. There are often the same tracks in the playlist and the order seems to repeat too. I even got the feeling it doesn’t include all the tracks and just shuffles a subset of them.

It seems like I am not alone with the problem and there is already a bugreport.

So I tried the mobile winamp player. I was not too optimistic since the desktop version of it just evolved to a big fat monster. But I was positively surprised. The player looks nice, is fast and is better at shuffling. I had songs in the playlist again I missed for quite some time now.

The only thing that is not too great is the user interface uses a lot of small button elements. This is not so nice when you use it in your car. Additionally you can’t switch tracks using the little forward / backwards buttons, when the screen is locked but that is not a deal breaker.

Did you have the same experience with android music player? Let me know.