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• Revision 9347e55f12 : Making c++ compiler happier. Change-Id : Ie224e968589bdb0774dc112e6f6df56cc04474

  21 mars 2014, par Dmitry Kovalev

  Changed Paths :
   Modify /vp9/decoder/vp9_decodeframe.c

  
   Modify /vp9/decoder/vp9_decodemv.c

  
  
  Making c++ compiler happier.

  Change-Id : Ie224e968589bdb0774dc112e6f6df56cc0447465

• Pipe video frames from ffmpeg to canvas without loading the entire video into memory

  1er janvier 2024, par Aviato

  I am working on a project that involves frame manipulation and I decided to choose node canvas API for that. I used to work with OpenCV Python and there was a cv2.VideoCapture class that takes a video as input and prepares to read the frames of the video and we can loop through the frames one at a time without having to load all the frames at once in memory.
Now I tried a lot of ways to replicate the same using ffmpeg, i.e. trying to load frames from a video in an ordered, but "on-demand," fashion.

  


  I tried using ffmpeg as a child process to process frames and standout the frames.

  


  const spawnProcess = require('child_process').spawn,
    ffmpeg = spawnProcess('ffmpeg', [
        '-i', 'test.mp4',
        '-vcodec', 'png',
        '-f', 'rawvideo',
        '-s', '1920*1080', // size of one frame
        'pipe:1'
    ]);
ffmpeg.stdout.on('data', (data) => {
    try {
        // console.log(tf.node.decodeImage(data).shape)
        console.log(`${++i} frames read`)
        //context.drawImage(data, 0, 0, width, height)
        
        
    } catch(e) {
        console.log(e)
    } 
})


  


  The value in the console shows something around 4000 + console logs, but the video only had 150 frames, after much investigating and console logging the data, I found that was buffer data, and it's not processing it for each frame. The on-data function returns the buffer data in an unstructured way
I want to read frames from a video and process each one at a time in memory, I don't want to hold all the frames at once in memory or in the filesystem.

  


  

  


  I also want to pipe the frames in a format that could be rendered on top of a canvas using drawImage

  


• Making a ffmpeg screen capture on Mac OS X using YUV 4:2:0 Planar color model

  30 mai 2019, par Bass

  I make screen recordings with ffmpeg, using avfoundation on Mac OS X, x11grab on Linux and gdigrab on Windows.

  The resulting files should be compatible with modern web browsers (<video></video>), so I use H.264 codec and request YUV 4:2:0 Planar pixel format.

  On Mac OS X, however (unlike Linux and Windows), I receive the following logging :

  /usr/local/bin/ffmpeg -y -v error -f avfoundation -threads 0 -hide_banner -i 1:none -f mp4 -vcodec h264 -pix_fmt yuv420p -r 25/1 -qscale:v 1 -vf scale=-1:1080 target.mp4
  
  [avfoundation @ 0x7fdba2003a00] Selected pixel format (yuv420p) is not supported by the input device.
  
  [avfoundation @ 0x7fdba2003a00] Supported pixel formats:
  
  [avfoundation @ 0x7fdba2003a00]   uyvy422
  
  [avfoundation @ 0x7fdba2003a00]   yuyv422
  
  [avfoundation @ 0x7fdba2003a00]   nv12
  
  [avfoundation @ 0x7fdba2003a00]   0rgb
  
  [avfoundation @ 0x7fdba2003a00]   bgr0

  Still, according to mplayer, the resulting MP4 file seems to have YUV 4:2:0 Planar color model :

  [h264 @ 0x1048a8ac0]Format yuv420p chosen by get_format().
  
  [h264 @ 0x1048a8ac0]Reinit context to 1728x1088, pix_fmt: yuv420p
  
  [h264 @ 0x1048a8ac0]Format yuv420p chosen by get_format().
  
  [h264 @ 0x1048a8ac0]Reinit context to 1728x1088, pix_fmt: yuv420p
  
  [swscaler @ 0x1048c3cc0]bicubic scaler, from yuv420p to yuyv422 using MMXEXT
  
  *** [scale] Exporting mp_image_t, 1728x1080x12bpp YUV planar, 2799360 bytes
  
  *** [vo] Allocating mp_image_t, 1728x1080x16bpp YUV packed, 3732480 bytes

  the same confirmed by ffmpeg :

  $ ffmpeg -i target.mp4 -hide_banner
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'target.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf58.20.100
  
    Duration: 00:00:04.72, start: 0.000000, bitrate: 201 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1728x1080, 197 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler

  Questions :

  1. Can someone explain the above ffmpeg logging ?
  2. If I still need to convert the avfoundation video stream to yuv420p, how do I make it on the fly (in a single ffmpeg pass) ?