Sur d’autres sites (10805)

• Monster Battery Power Revisited

  28 mai 2010, par Multimedia Mike — Python, Science Projects

  So I have this new fat netbook battery and I performed an experiment to determine how long it really lasts. In my last post on the matter, it was suggested that I should rely on the information that gnome-power-manager is giving me. However, I have rarely seen GPM report more than about 2 hours of charge ; even on a full battery, it only reports 3h25m when I profiled it as lasting over 5 hours in my typical use. So I started digging to understand how GPM gets its numbers and determine if, perhaps, it’s not getting accurate data from the system.

  I started poking around /proc for the data I wanted. You can learn a lot in /proc as long as you know the right question to ask. I had to remember what the power subsystem is called — ACPI — and this led me to /proc/acpi/battery/BAT0/state which has data such as :

  present :                 yes
  capacity state :          ok
  charging state :          charged
  present rate :            unknown
  remaining capacity :      100 mAh
  present voltage :         8326 mV
  

  "Remaining capacity" rated in mAh is a little odd ; I would later determine that this should actually be expressed as a percentage (i.e., 100% charge at the time of this reading). Examining the GPM source code, it seems to determine as a function of the current CPU load (queried via /proc/stat) and the battery state queried via a facility called devicekit. I couldn’t immediately find any source code to the latter but I was able to install a utility called ’devkit-power’. Mostly, it appears to rehash data already found in the above /proc file.

  Curiously, the file /proc/acpi/battery/BAT0/info, which displays essential information about the battery, reports the design capacity of my battery as only 4400 mAh which is true for the original battery ; the new monster battery is supposed to be 10400 mAh. I can imagine that all of these data points could be conspiring to under-report my remaining battery life.

  Science project : Repeat the previous power-related science project but also parse and track the remaining capacity and present voltage fields from the battery state proc file.

  Let’s skip straight to the results (which are consistent with my last set of results in terms of longevity) :

  
  
  

  So there is definitely something strange going on with the reporting— the 4400 mAh battery reports discharge at a linear rate while the 10400 mAh battery reports precipitous dropoff after 60%.

  Another curious item is that my script broke at first when there was 20% power remaining which, as you can imagine, is a really annoying time to discover such a bug. At that point, the "time to empty" reported by devkit-power jumped from 0 seconds to 20 hours (the first state change observed for that field).

  Here’s my script, this time elevated from Bash script to Python. It requires xdotool and devkit-power to be installed (both should be available in the package manager for a distro).
  

  PLAIN TEXT

  PYTHON :

  1. # !/usr/bin/python
  2.  
  3. import commands
  4. import random
  5. import sys
  6. import time
  7.  
  8. XDOTOOL = "/usr/bin/xdotool"
  9. BATTERY_STATE = "/proc/acpi/battery/BAT0/state"
  10. DEVKIT_POWER = "/usr/bin/devkit-power -i /org/freedesktop/DeviceKit/Power/devices/battery_BAT0"
  11.  
  12. print "count, unixtime, proc_remaining_capacity, proc_present_voltage, devkit_percentage, devkit_voltage"
  13.  
  14. count = 0
  15. while 1 :
  16.   commands.getstatusoutput("%s mousemove %d %d" % (XDOTOOL, random.randrange(0,800), random.randrange(0, 480)))
  17.   battery_state = open(BATTERY_STATE).read().splitlines()
  18.   for line in battery_state :
  19.     if line.startswith("remaining capacity :") :
  20.       proc_remaining_capacity = int(line.lstrip("remaining capacity : ").rstrip("mAh"))
  21.     elif line.startswith("present voltage :") :
  22.       proc_present_voltage = int(line.lstrip("present voltage : ").rstrip("mV"))
  23.   devkit_state = commands.getoutput(DEVKIT_POWER).splitlines()
  24.   for line in devkit_state :
  25.     line = line.strip()
  26.     if line.startswith("percentage :") :
  27.       devkit_percentage = int(line.lstrip("percentage :").rstrip(’\%’))
  28.     elif line.startswith("voltage :") :
  29.       devkit_voltage = float(line.lstrip("voltage :").rstrip(’V’)) * 1000
  30.   print "%d, %d, %d, %d, %d, %d" % (count, time.time(), proc_remaining_capacity, proc_present_voltage, devkit_percentage, devkit_voltage)
  31.   sys.stdout.flush()
  32.   time.sleep(60)
  33.   count += 1

• Improper use of system() call ?

  28 mai 2013, par Dima1982

  I have a particle system program that generates a .dat file with particle coordinates in every iteration. The end goal is to run the program multiple times via a script with different parameters. So, I am trying to setup my program in a way that, for every run, all relevant data are going to be stored in a folder.

  What I do is to generate PNGs from the .dat files with Gnuplot, call ffmpeg to create a video out of the PNGs, use WinRAR to compress the .dat files and finally clean up, by deleting all the intermediate files. This works, when I do it in the working directory.

  Now I try to create a new directory and do the same stuff in there. My code :

  // Load the proper library to use chdir() function
  
  #ifdef _WIN32
  
  #include 
  
  #elif defined __linux__ || defined __APPLE__&&__MACH__
  
  #include 
  
  #endif
  
  
  
  // Make output directory and change working directory to new directory
  
      ostringstream dirCommand;
  
      dirCommand << "mkdir " << folderName_str;
  
      system(dirCommand.str().c_str());
  
      const char* test  = folderName_str.c_str();
  
      #ifdef _WIN32
  
          if(_chdir(test))
  
          {
  
              printf( "Unable to locate the directory: %s\n",test);
  
              return;
  
          }
  
      #elif defined __linux__ || defined __APPLE__&&__MACH__
  
          if(chdir(test))
  
          {
  
              printf( "Unable to locate the directory: %s\n",test);
  
              return;
  
          }
  
      #endif
  
          else
  
              printf("Created output directory...\n");

  Already for this part, I know that there are going to be objections. I have looked extensively on SO and many people favor SetCurrentDirectory() for Windows, or they are skeptical about using system(). In my defense, I am a novice programmer and my knowledge is really limited...

  Now, when I try to make the video with FFMpeg and then rar/tar my files :

  // Make video
  
          std::cout << "Generating Video..." << endl;
  
          ostringstream command;
  
          command << "ffmpeg -f image2 -r 1/0.1 -i output_%01d.png -vcodec mpeg4 " << videoName_str << ".avi -loglevel quiet";
  
          std::system(command.str().c_str());
  
  
  
          // Clean Up!
  
          std::cout << "Cleaning up!" << endl;
  
          ostringstream command2;
  
          #ifdef _WIN32
  
              command2 << "rar -inul a " << videoName_str << ".rar *.dat settings.gp loadfile.gp";
  
          #elif defined __linux__ || defined __APPLE__&&__MACH__
  
              command2 << "tar cf " << videoName_str << ".tar *.dat settings.gp loadfile.gp";
  
          #endif
  
          std::system(command2.str().c_str());

  I get very different behaviors in Win/ Linux.

  Win 7 x64, Visual Studio 2010/12

  In windows, the folder is created. The .dat files are generated correctly and gnuplot plots the PNGs as well. When ffmpeg is called, nothing happens. No error message from FFMpeg or anything. The same goes for WinRAR. Maybe, for the last thing, I can use the command line utility of 7z which is free !

  Linux Mint 14 x64, Qt 4.8.1

  Strangely enough, the behavior is inverted from that of Windows. As soon as the dir is changed, only the first .dat file is generated. It is as if every subsequent call I make to fprintf() for my file generation does not work, or gets lost somewhere. Gnuplot works, as do ffmpeg and tar !!

  I am really perplexed. Any help, would be really appreciated.

• How to quit pexpect launched ffmpeg with key q pressed

  25 février 2014, par Shuman

  i used pexpect to call ffmpeg which is a lengthy process. it took half an hour, how can i detect user has pressed q key to stop it ? just like when you press q when using ffmpeg command line tool

  the ffmpeg command line is
  ffmpeg -y -i url -c copy -absf aac_adtstoasc out.mp4

  the last line of ffmpeg output is

  ...
  
  Stream mapping:
  
    Stream #0:1 -> #0:0 (copy)
  
    Stream #0:2 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  frame=   84 fps= 77 q=-1.0 Lsize=  184626kB time=00:00:06.96 bitrate=217120.3kbits/s

  the code i have now is

  reo = re.compile("""\S+\s+(?P\d+)  # frame
  
                       \s\S+\s+(?P<fps>\d+)           # fps
  
                       \sq=(?P<q>\S+)                    # q
  
                       \s\S+\s+(?P<size>\S+)          # size
  
                       \stime=(?P<time>\S+)           # time
  
                       \sbitrate=(?P<bitrate>[\d\.]+) # bitrate
  
                       """, re.X)
  
  
  
  durationReo = (&#39;(?&lt;=Duration:\s)\S+(?=,)&#39;)
  
  
  
  cpl = thread.compile_pattern_list([
  
      pexpect.EOF,
  
      reo,
  
      durationReo
  
  ])
  
  
  
  while True:
  
      i = thread.expect_list(cpl, timeout=None)
  
      if i == 0: # EOF
  
          print "the sub process exited"
  
          break
  
      elif i == 1:
  
          frame_number = thread.match.group(0)
  
          print frame_number
  
          print reo.search(frame_number).groups()
  
          # thread.close
  
      elif i == 2:
  
          durationLine = thread.match.group(0)
  
          print &#39;Duration:&#39;, durationLine
  
          # print "something :",thread.match.group(1)
  
          pass
  
  </bitrate></time></size></q></fps>

  with this code i can already get the frame info and duration info, the ultimate goal is to create a textual progress bar with another python progressbar module. but with the ability to send the 'q' pressed signal to ffmpeg child process.