Perl system call mplayer, transition between videos varies

Question

I'm only few weeks into perl, and I am trying to run the codes below:

sub runVideo {
    system('mplayer -fs video1.mpeg2 video2.mpeg2');
    return;
}

runVideo();
system('some other processes in background&');
runVideo();

Basically I run video1 and video2 for two times, first time which is just the videos, second time with some application running at the background, doesn't matter what apps are running, since I'm running the videos in fullscreen mode.

Problem:

On the first run, the transition from video1 to video2 takes about 1-2 seconds. While on the second run, the transition from video1 to video2 takes less than a second.

Question:

Why is the transition time differs? Could it be the videos are still in the memory so it took shorter time to load it?

What other alternatives or workarounds to get a same transition time?

Answer 1

The answer is likely in caching effects. Either the video, or the codecs required to play it, weren't in memory for video2. But of course the second time you do it, they are.

There are a couple of things you can try—depending on the exact reason the delay is a problem:

• You can try the -fixed-vo option to mplayer (if you're using mplayer 1.x; its default in 2.x I believe). This will prevent the jarring vo deinit/reinit cycle.
• You can (and probably should) run mplayer in -slave mode (also probably with -idle). This will give you much more control over it.
• You can pre-cache whatever data is taking a while. The way to do this on Unix-like systems is posix_fadvise(int fd, off_t offset, off_t len, int advice) with an advice of POSIX_FADV_WILLNEED. Alternatively, on Linux, readahead(int fd, off64_t offset, size_t count). Or finally, by a mmap on the file, followed by madvise(void *addr, size_t length, int advice) with advice of MADV_WILLNEED. Unfortunately, none of posix_fadvise, readahead, and madvise are exported by the POSIX module. So you'll have to find another module (check CPAN) or resort to Inline or XS. Or open/sysread (less efficient).
• You can combine your videos together. That should completely eliminate transition time.