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• Filename in android rejected by ffmpeg command

  28 avril 2020, par ark1974

  Planning to use ffmpeg in Android for A/V conversion. Installed Android Studio 3.5.3. I am fairly new to Android development and the folder names, unlike in windows system, is fairly confusing to me. I am able to build the gradle without any error but the fetched pathname is rejected by ffmpeg commandline.

  



  Questions :

  



  1) Resulting path_name shows both pathname and filename which is cool. Is the resulting path_name correct or expected ? However, ffmpeg raised error flag citing that directory/file do not exist corresponding to the resulting path_name.

  



  2) Inside android properties, the path starts with "Device storage/..." but Android Studio command starts with "/document/". Why I see this variation ?

  



  3) onActivityResult() do not work with @override private prefix but works with @override public, is it expected ? Many examples on internet, however use private though.

  



  4) MediaStore.Audio.Media.DATA code do not work at all, is it deprecated in Android 3.5.5 ?

  



  Java code :

  



  @Override public void onActivityResult(int requestCode, int resultCode, Intent data) {
        if(requestCode == 7 &&  resultCode == RESULT_OK){    
                    path_name = data.getData().getPath();    
        }
    }


  



  Result :

  



  path_name = "/document/primary:WhatsApp/Media/WhatsApp Audio/AUD-20200402-WA0006.mp3" **strong text**


  


• Use FFMPEG to blend streaming overlay onto second stream

  31 août 2017, par Louwrens Benade

  I’m trying to build a form of monitoring that can be superimposed onto a live stream.

  Monitor Overlay

  ffmpeg -i rtmp://localhost/pool/livestream -filter_complex \
  
    "nullsrc=1024x576[1:v]; \
  
    [0:a]showvolume=v=0:o=1:t=0:f=0.1,drawbox=x=ih-40:y=0:w=40:h=ih[volume]; \
  
    [1:v]drawtext=x=(main_w/2)-(text_w/2):y=text_h:fontsize=30:fontcolor=white:borderw=1:text='Stream Label',scale=-1:-1[label]; \
  
    [label][volume]overlay=x=main_w-40:y=0[output]" \
  
    -map "[output]" -f flv rtmp://localhost/pool/livestream_overlay

  What I would like to accomplish is that this stream be superimposed onto the original stream and pushed to a third RTMP endpoint, like this :

  ffmpeg -i rtmp://localhost/pool/livestream -i rtmp://localhost/pool/livestream_overlay \
  
    -filter_complex "[0:v][1:v]overlay=shortest=1[output]" \
  
    -f flv rtmp://localhost/pool/livestream_monitor

  While the workflow seems to be working, the overlay is not blending (subtracted ?) onto the original video :

  Actual output

  

  Expected output

  

  Note : codec options have been removed for brevity’s sake.

• How would I assign multiple MMAP's from single file descriptor ?

  9 juin 2011, par Alex Stevens

  So, for my final year project, I'm using Video4Linux2 to pull YUV420 images from a camera, parse them through to x264 (which uses these images natively), and then send the encoded stream via Live555 to an RTP/RTCP compliant video player on a client over a wireless network. All of this I'm trying to do in real-time, so there'll be a control algorithm, but that's not the scope of this question. All of this - except Live555 - is being written in C. Currently, I'm near the end of encoding the video, but want to improve performance.

  To say the least, I've hit a snag... I'm trying to avoid User Space Pointers for V4L2 and use mmap(). I'm encoding video, but since it's YUV420, I've been malloc'ing new memory to hold the Y', U and V planes in three different variables for x264 to read upon. I would like to keep these variables as pointers to an mmap'ed piece of memory.

  However, the V4L2 device has one single file descriptor for the buffered stream, and I need to split the stream into three mmap'ed variables adhering to the YUV420 standard, like so...

  buffers[n_buffers].y_plane = mmap(NULL, (2 * width * height) / 3,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset);
  
  buffers[n_buffers].u_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 1) /
  
                                      sysconf(_SC_PAGE_SIZE));
  
  buffers[n_buffers].v_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 
  
                                      width * height / 6 + 1) / 
  
                                      sysconf(_SC_PAGE_SIZE));

  Where "width" and "height" is the resolution of the video (eg. 640x480).

  From what I understand... MMAP seeks through a file, kind of like this (pseudoish-code) :

  fd = v4l2_open(...);
  
  lseek(fd, buf.m.offset + (2 * width * height) / 3);
  
  read(fd, buffers[n_buffers].u_plane, width * height / 6);

  My code is located in a Launchpad Repo here (for more background) :
  http://bazaar.launchpad.net/ alex-stevens/+junk/spyPanda/files (Revision 11)

  And the YUV420 format can be seen clearly from this Wiki illustration : http://en.wikipedia.org/wiki/File:Yuv420.svg (I essentially want to split up the Y, U, and V bytes into each mmap'ed memory)

  Anyone care to explain a way to mmap three variables to memory from the one file descriptor, or why I went wrong ? Or even hint at a better idea to parse the YUV420 buffer to x264 ? :P

  Cheers ! ^^