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• Building ffmpeg on mac results in undefined symbols

  9 juin 2017, par Peter

  Environment : macOS 10.12.5, Xcode 8.3.3, pkg-config installed via brew

  I need to build a minimal version of ffmpeg that supports H.264 decoding. I have downloaded the source for ffmpeg version 3.3.1 and have successfully built it for Windows and Linux. Now, I am trying to build it for mac.

  The specific flags of the configuration that are relevant are :

  --disable-yasm
  
  --disable-everything
  
  --enable-decoder=h264
  
  --enable-decoder=h264_vda
  
  --enable-vda

  After running the configuration, when I run make, all the libraries such as libavcodec.a, libavfilter.a, libavformat.a, are built. However, ffmpeg itself does not get built. The error I get is :

  Undefined symbols for architecture x86_64:
  
    "_ff_vda_create_decoder", referenced from:
  
        _vdadec_init in libavcodec.a(vda_h264_dec.o)
  
    "_ff_vda_destroy_decoder", referenced from:
  
        _vdadec_init in libavcodec.a(vda_h264_dec.o)
  
        _vdadec_close in libavcodec.a(vda_h264_dec.o)
  
  ld: symbol(s) not found for architecture x86_64

  Looks like the functions are defined in ./libavcodec/vda_h264.c. However, it appears vda_h264.c is never compiled. Other vda related files such as vda.c and vda_h264_dec.c do get compiled (and added to libavcodec.a).

  I am thinking perhaps I am missing a configuration flag. Can someone please help ? Regards.

• avcodec/eatgv : Check remaining size after the keyframe header

  28 juillet 2019, par Michael Niedermayer

  avcodec/eatgv : Check remaining size after the keyframe header
  The minimal size which unpack() will not fail on is 5 bytes
  
  Fixes : Timeout (14sec -> 77ms) (testcase 15508)
  
  Fixes : 15508/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EATGV_fuzzer-5700053513011200
  
  Fixes : 15996/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_EATGV_fuzzer-5751353223151616
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/eatgv.c

• Pipe numpy array to virtual video device

  16 mars 2021, par sre

  I want to pipe images to a virtual video device (e.g. /dev/video0), the images are created inside a loop with the desired frame rate.

  


  In this minimal example i only two arrays which alternate in the cv2 window. Now i look for a good solution to pipe the arrays to the virtual device.

  


  I saw that ffmpeg-python can run asynchronous with ffmpeg.run_async(), but so far i could not make anything work with this package.

  


  example code without the ffmpeg stuff :

  


  #!/usr/bin/env python3

import cv2
import numpy as np
import time

window_name = 'virtual-camera'
cv2.namedWindow(window_name, cv2.WINDOW_GUI_EXPANDED)

img1 = np.random.uniform(0, 255, (1080, 1440, 3)).astype('uint8')
img2 = np.random.uniform(0, 255, (1080, 1440, 3)).astype('uint8')

for i in range(125):
    time.sleep(0.04)
    if i % 2:
        img = img1
    else:
        img = img2
    cv2.imshow(window_name, img)
    cv2.waitKey(1)
cv2.destroyAllWindows()