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• How can I capture low resolution video on Android reliably across a range of devices ?

  26 octobre 2015, par MisterMat

  Hello Android video experts :)

  I am developing an Android application which allows the user to capture video and upload it to a remote server (it’s more involved than that but the rest of the app is not important). Because of the upload requirement, it is important that the video is of a reasonable size, so not super high resolution. Let’s say a max of 680x480 or 10Mb/minute. This is no problem on Apple devices.

  I have had what can only be described as a complete nightmare trying to capture video at a reasonably low bitrate reliably across a range of Android devices.

  As I understand it there are two ways of capturing video on Android :

  1) Using the Media Recorder/Camera API

  2) Using an Intent to open the cameras video capture application

  Option 1) gives the most flexibility and allows us to easily change the capture resolution. However the Android Camera API is NOT reliable across a range of devices, and I have very good information (including from someone who liaised with Google on this issue) that if you capture video using this API then it will crash on a good 50% of the devices out there. There is a reason that Zoom Camera FX uses an Intent for video capture. Zoom Camera (different app) seems to use Media Recorder, but has lots of bad reviews for video crashing or not working.

  Option 2) works well across a range of devices, as it uses the in built application on the device. The trouble is you have no control whatsoever on the resolution, there is a quality hint on the Intent but the camera app will normally ignore this. My Samsung Galaxy S3 records video by default at about 2Mb/s. This is way too high resolution. The built in application can of course change the resolution, but this relies on action by the user which is difficult to control.

  I understand that I could use a library such as ffmpeg to change the resolution of the video after capture. However this requires me to compile the library for Android, and also I have been informed that in order to legally use the decode/encode codecs on the device you have to pay license fees that amount to about $1 per copy of the app. Since this app will be free to use, this is not an option.

  So that’s where I’m at. I’ve searched long and high for answers, but I can’t figure out how to capture low resolution video reliably using Android.

  Any help very much appreciated !

  Matthew

• avformat/mov_muxer : Extended MOV muxer to handle EVC video content

  15 juin 2023, par Dawid Kozinski

  avformat/mov_muxer : Extended MOV muxer to handle EVC video content
   Changes in mov_write_video_tag function to handle EVC elementary stream
  
   Provided structure EVCDecoderConfigurationRecord that specifies the decoder configuration information for ISO/IEC 23094-1 video content
  Signed-off-by : Dawid Kozinski <d.kozinski@samsung.com>
  

  • [DH] libavformat/Makefile
  • [DH] libavformat/evc.c
  • [DH] libavformat/evc.h
  • [DH] libavformat/isom_tags.c
  • [DH] libavformat/movenc.c

• Can I create a proccess to kill blocked processes in a queue with Python ?

  15 mars 2017, par user3182473

  I would like to create a process, which kills blocked processes in a queue. These processes are actually ’ffmpeg’ command in my work, which are unstable and blocked occasionally.

  For simplicity I use ’echo’ instead of ’ffmpeg’ as example here. I found that the alive process become ’finished’ from the queue, and the subprocess returncode is 0. Why ?

  And can anyone tell how I can modify my code with python2.7 to fit this requirement ? Any suggestion would be appreciated.

  import subprocess
  
  import os
  
  import multiprocessing
  
  import time
  
  
  
  cmds = ['echo "a" &sleep 10','echo "b"']
  
  queue = multiprocessing.Queue(maxsize=3)
  
  
  
  class ProcessKiller(multiprocessing.Process):
  
      def __init__(self,queue):
  
          multiprocessing.Process.__init__(self)
  
          self.queue = queue
  
  
  
      def run(self):
  
          while True:
  
              try:
  
                  proc = self.queue.get(block=False)
  
                  print 'bbbbb',proc.poll(),proc.pid #WHY HERE THE RETURNCODE=0?
  
                  if proc.poll() is None:
  
                      print 'tokill'
  
                      time.sleep(5)
  
                      if proc.poll() is None:
  
                          os.killpg(os.getpgid(proc.pid),signal,SIGTERM)
  
                          print 'killed'
  
              except Exception as e:
  
                  time.sleep(0.5)
  
  
  
  pk = ProcessKiller(queue)
  
  pk.start()
  
  
  
  for item in cmds:
  
      cmd = subprocess.Popen(item,preexec_fn=os.setsid,shell=True)
  
      print 'aaaaa',cmd.poll(), cmd.pid
  
      queue.put(cmd,block=False)
  
  
  
      time.sleep(3)        
  
      print 'cccc',cmd.poll()
  
  
  
      time.sleep(10)
  
      print 'dddd', cmd.poll()
  
      cmd.communicate()
  
  
  
      print 'finished'

  The result from this script :

  aaaaa None 120748
  
  a
  
  bbbbb 0 120748
  
  cccc None
  
  dddd 0
  
  finished
  
  aaaaa None 120755
  
  b
  
  bbbbb 0 120755
  
  cccc 0
  
  dddd 0
  
  finished

  UPDATE : Now I use a while loop to monitor the status of the subprocess. It works. However, I am still curious why the status of the process changes from the queue.