At the answer to the question on Stack and in the book at here on page 52 I found the normal getTickCount getTickFrequency combination to measure time of execution gives time in milliseconds . However the OpenCV website says its time in seconds. I am confused. Please help...
There is no room for confusion, all the references you have given point to the same thing.
getTickCount gives you the number of clock cycles after a certain event, eg, after machine is switched on.
A = getTickCount() // A = no. of clock cycles from beginning, say 100
process(image) // do whatever process you want
B = getTickCount() // B = no. of clock cycles from beginning, say 150
C = B - A // C = no. of clock cycles for processing, 150-100 = 50,
// it is obvious, right?
Now you want to know how many seconds are these clock cycles. For that, you want to know how many seconds a single clock takes, ie clock_time_period. If you find that, simply multiply by 50 to get total time taken.
For that, OpenCV gives second function, getTickFrequency(). It gives you frequency, ie how many clock cycles per second. You take its reciprocal to get time period of clock.
time_period = 1/frequency.
Now you have time_period of one clock cycle, multiply it with 50 to get total time taken in seconds.
Now read all those references you have given once again, you will get it.
dwStartTimer=GetTickCount();
dwEndTimer=GetTickCount();
while((dwEndTimer-dwStartTimer)<wDelay)//delay is 5000 milli seconds
{
Sleep(200);
dwEndTimer=GetTickCount();
if (PeekMessage (&uMsg, NULL, 0, 0, PM_REMOVE) > 0)
{
TranslateMessage (&uMsg);
DispatchMessage (&uMsg);
}
}
Related
I would like to know whether there is a difference between the "Counter" and the count maintained by the "Meter" class? I understand the Meter measures rates too, but I am curious to know whether if there were a counter and a meter updated(incremented for Counter) at the same time, I would think both numbers would be same. Am I wrong in this assumption?
the Meter simply also keeps track of the count of mark events that you have on the meter. It does so in the same way a counter does, thus the Meter is just an object that holds the internals of the counter + the logic to measure the rates of the occurring events too.
Here is a code example:
public class MetricTest {
public static void main(String[] args) {
MetricRegistry r = new MetricRegistry();
Counter counter = r.counter("counter");
Meter meter = r.meter("meter");
counter.inc();
meter.mark();
System.out.println(counter.getCount());
System.out.println(meter.getCount());
counter.inc(10);
meter.mark(10);
System.out.println(counter.getCount());
System.out.println(meter.getCount());
}
}
Which will print:
1
1
11
11
So yes, if the counter and meter are updated in the same way, they will have the same count. The meter uses the count additionally to calculate the mean rate (in addition to the 1/5/15 - minute one)
I hope that helps,
Artur
Counter can be decremented. Meter can not be decremented. So, when counter and meter are used together, the values of "counters" differ when the Counter value is decremented.
I'm working on a game in Xcode 6 and need to generate a new random number each time 2 specific objects touch each other. I have tried using srand() at the start of my application but it seems that the values remain the same as if it isn't seeding a new value each time the objects collide.
here is the code
if((CGRectIntersectsRect(Stickman.frame, Box1.frame))) {
xRan = arc4random()%11;
if(xRan<=3){
Spike1 = true;
[self SpikeCall];
}
//Gold
if (xRan==10) {
G1 = true;
}
Box1.center = CGPointMake(0,278);
Box1SideMovement = 5;
}
The problem is that after the Stickman hits the Box1 when it comes back on screen it still holds the same value in xRan except for certain scenarios where it will between 1-3 then it makes Spike1 true. I'd like it to be so that each time the object Box1 intersects with Stickman the xRan seeds a new number between 1-10 so that there is a 1 in 10 chance of G1 becoming true & if xRan is 1-3 it will make Spike1 true.
This is more of a comment than an answer, but it's too long for a comment.
There are a couple of problems with your approach here. First, srand does not seed the arc4random function. It seeds the rand function, which is a different pseudo-random number generator with somewhat worse properties than arc4random. There is no explicit seeding function for arc4random. Second, if you want a random number between 1 and 10 you should not use the % 11 approach. That gives you a random number between 0 and 10 (and I think you don't want zero), but also it probably does not give you a uniform distribution. Even if arc4random is good at providing a uniform distribution in its whole range it may not provide a uniform distribution of the least significant bits.
I suggest you use something like:
arc4random_uniform(10) + 1
arc4random_uniform(10) will return a number between 0 and 9, and will do a good job of providing a uniform distribution in that range. The +1 just shifts your interval so you get numbers between 1 and 10 instead of between 0 and 9.
I have audio files, with different durations. They have common content and unique content. E.g. two files, 70 seconds each, last 10 seconds of the first file is the same as first two seconds of the second file. How can I find the exact position of common content (e.g. 60.0 of the first file)?
Sounds a little bit messy, hope the following image can help https://drive.google.com/file/d/0BzBE2Kfw8uQoUWNTN1RXOEtLVEk/view?usp=sharing
So, I'm looking for the red mark - common content starts at 60.0 sec of the first file.
The problem is that I have files with different durations. Sometimes it's 70 seconds long, sometimes one file is 70 seconds, the other is 80 seconds long, etc. Most likely they have 60.0 seconds of unique content, but I'm not sure (it could be 59.9 of unique content, etc.).
Thus, I assume I need to get a short snippet of the second file from first 10 seconds and find it in the first file:
For example, output: 2.5 sec of the second file = 62.5 from the first file - works for me, as well.
THE MAIN GOAL IS TO PLAY FILE AFTER FILE GAPLESS. If I get the values, I'll be able to do this. Sometimes the values can be: 2.5 = 63.7, that's why I need the exact match.
Can anybody help with the code or at least some information of how to compare two snippets of audio content? Thanks in advance!
Wow, that is quite a problem to solve. And I must confess that i've not done anything exactly like this or have any code based suggestions.
All I will say is that if I were looking to try and solve this problem, then I would try and save the audio file as some kind of uncompressed and fixed size (as in a known number of bytes per second) format.
Then you could take a section of one file and byte match it with another, then you would know how many bytes inwards that snippet occurred. Then, knowing the bytes per ms (sort of frame size), you could work out the exact time position.
It's a bit hair brained, but i've used that technique with images before but at least audio is linear!
Here is an approximate example of how I would go about doing the comparison of a sample within a sound file.
- (int)positionOf:(NSData*)sample inData:(NSData*)soundfile {
// the block size has to be big enough to find something genuinely unique but small enough to ensure it is still fast.
int blockSize = 128;
int position = 0;
int returnPosition = INT32_MAX;
// check to see if the block size exceeds the sample or data file size
if (soundfile.length < blockSize || sample.length < blockSize) {
return returnPosition;
}
// create a byte array of the sample, ready to use to compare with the shifting buffer
char* sampleByteArray = malloc(sample.length);
memcpy(sampleByteArray, sample.bytes, sample.length);
// now loop through the sound file, shifting the window along.
while (position < (soundfile.length - blockSize)) {
char* window = malloc(blockSize);
memcpy(window, soundfile.bytes + position, blockSize);
// check to see if this is a match
if(!memcmp(sampleByteArray, window, blockSize)) {
// these are the same, now to check if the whole sample is the same
if ((position + sample.length) > soundfile.length) {
// the sample won't fit in the remaining soundfile, so it can't be this!
free(window);
break;
}
if(!memcmp(sampleByteArray, soundfile.bytes + position, sample.length)) {
// this is an entire match, position marks the start in bytes of the sample.
free(window);
returnPosition = position;
break;
}
}
free(window);
position++;
}
free(sampleByteArray);
return returnPosition;
}
It compiles, didn't have time to setup the scenario to check your exact case, but i'm quite confident this may help.
Could somebody be so kind as to point me towards some erlang code which allows me to time how long it takes to run certain pieces of code?
I havent seen an erlang library where this is available?
You can use the erlang:statistics function.
This is used in Joe Armstrong's Programming Erlang book (p141).
e.g.
yourfun() ->
statistics(runtime),
statistics(wall_clock),
% your code here
{_, Time1} = statistics(runtime),
{_, Time2} = statistics(wall_clock),
U1 = Time1 * 1000,
U2 = Time2 * 1000,
io:format("Code time=~p (~p) microseconds~n",
[U1,U2]).
In this example U1 is the CPU time and U2 is the total elapsed time (wall clock time).
There is the timer library; check tc/[1-3].
You can also use erlang:now/0 to collect timestamps and then calculate the duration (now_diff/2 is really useful for that).
Take a look at timer:tc(Module, Function, Arguments)
I have this line, which shows the minutes and seconds. But I have to add milliseconds to it as well for greater accuracy. How do I add that in this line, or is there an easier way to get the desired result?
#duration = [cd.ExactDuration/60000000, cd.ExactDuration/1000000 % 60].map{|t| t.to_s.rjust(2, '0') }.join(':'))
The exact duration type is saved in microseconds. So the first converts to microseconds to minutes, the second part is microseconds to seconds. Now I need to add milliseconds.
cd.ExactDuration/1000 % 1000 should do the trick.
Of course you may also want to tweak the formatting, since that's a datum you don't want to right-justify in a 2-wide field;-). I'd suggest sprintf for string-formatting, though I realize its use is not really intuitive unless you come from a C background.