Recherche avancée

Sur d’autres sites (6462)

• Immidiately display first and latest frame of h264 stream which may sometimes pause

  22 septembre 2016, par jorp

  Steps to reproduce :

  1.Connect android device to linux PC via USB.
  

  2.Run command on pc :
  adb shell screenrecord --output-format=h264 - | ffplay -analyzeduration 1 -

  3.Screenrecord(an Android system tool) will start to capture Android screen, encode by MediaCodec, generate h264 stream, send stream data to ffplay via pipe.

  4.PC will pop up ffplay window, and start display Android screen graphs

  ---

  If adb command runs when Android screen graph keeps static (no pixel color changes), ffplay window won’t pop up, until I touch somewhere to make Android graph changes.

  Question 1 : how to make ffplay to immidiately display the first frame of video when Android screen keeps static and adb commmand runs ?

  I’m not talking about "latency", if Android graph keeps changing, the graphic latency is within 2 second. It’s fast enough.

  when Android graph is static, run command without ffplay :
  adb shell screenrecord --output-format=h264 -

  screenrecord will output H264 stream data immidiately then pause.(See picture below).
  stream data comes first

  Does the data contain all information of first frame graph ?
  If so, how to make ffplay to display it immidiately ?

  ---

  Question 2 : how to make ffplay to immidiately display the latest frame of video when Android screen suddenly become static ?

  When Android screen start casting and Android graph suddenly become static, H264 data stream transfer will pause, while PC graph is different with Android graph.

  For example, I make a popup menu on Android disappear, there has been a fadeoff animation, PC graph pauses and display a translucent popup menu.(See picture below)

  latest graph on pc

  The first and latest frames of stream doesn’t display in ffplay immidiately, they are "missing".
  when Android screen go on changing, the "missing" frames displays.
  So it seems like the latest frames are always in buffer.

  I’ve tried adding these params to ffplay :
  

  -noinfbuf
-fflags nobuffer
-max_delay 0
-sync ext
-preset ultrafast
-tune zerolatency

  
  They cannot solve the problems

  Modifing Android ROM or screenrecord source, making a pixel color changes every frame, may solve the problems(I guess), but it would enlarge data stream, it’s the last choise.
  Is there any solution by adding params of ffplay, or by modifing screenrecord or ffplay source code ?

  PS : mplayer also has the same problem :
  mplayer -demuxer h264es -

• how to use ffmpeg in python to record a specific window with system audio without command line and cleanly stop it

  17 juillet 2023, par Jaime

  I'm working in an application that is capturing specific window from my desktop and grabbing the system audio, it application is packaged with pyinstaller with —windowed parameter, when I start to capture video it work perfectly and in a debbug execution it stop cleanly, but when I run it from the packaged file, the ffmpeg process never stop. I'm using subprocess.popen to launch ffmpeg by this way :

  


  command = ['ffmpeg','-f', 'dshow', '-i', f'audio={device}', '-f', 'gdigrab', '-framerate', '30', '-i', f'title={device_model}', '-c:v', 'libx264', '-preset', 'slower', '-crf', '22', f'{file_path}']
subprocess.Popen(comando,stdin=subprocess.PIPE,stdout=subprocess.PIPE,stderr=subprocess.PIPE,shell=False)


  


• create associative data from ffmpeg string result into python

  9 septembre 2018, par Question

  To perform video operations I’m using python with the support of ffmpeg. After I’ve uploaded videos, I need to resize them, so I’ll follow these instructions to calculate the video dimensions :

  link_v = "C:/video/video.mp4"
  
  ffmpeg = "ffprobe -v error -show_entries stream=width,height -of default=noprint_wrappers=1 %s"% link_v
  
  info = check_output(ffmpeg, shell=True)
  
  print(info)

  The console result is something like this :

  width=350
  
  height=350

  But I do not care about this, when it is printed as if it were a string, because the real data would be : b’width=350\r\nheight=350\r\n’ or [’width=350\r\nheight=350\r\n’].

  What I really want to see is an associative data : "width : 350, height : 350", once I get then I would call for example width in the info mode [’width’], how can I get this result ?