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• How can I download a video with url beginning with blob:https://…

  11 août 2017, par iMax

  I would like to know if it is possible to download a video from a URL beginning with blob :

  blob:https://www.xyz123…

  i would prefer a terminal solution (ffmpeg ?, youtube-dl ?). but i have not found anything on the world wide web.

  Again : I have the url of the video stream, which looks like the above. How can I download the complete video ?

  Update

  Ok. I now found a webpage which allowed me to download the video file I wanted :
  https://video-download.online/

  But I am still wondering if there is a Terminal solution for downloading video with blob-URL (like in arte mediathek [ example arte ] or in zdf mediathek [ example zdf ]).

  Does nobody know how to do it ?

• how to use the H264 video encoder with ffmpeg / opencv2 ?

  30 août 2023, par Vince

  I am on ubuntu 22.04.

  


  I installed ffmpeg with apt.

  


  I am creating a video from some image files using python/opencv2 (installed via pip)

  


  When I use :

  


  cv2.VideoWriter_fourcc(*"mp4v")


  


  the video is successfully created, but is not supported by firefox.

  


  I read online that the H264 encoder would be a better fit for web-browsers supports.

  


  ffmpeg -codecs | grep h264 


  


  shows :

  


  


  DEV.LS h264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders : h264 h264_v4l2m2m h264_qsv h264_cuvid ) (encoders : libx264 libx264rgb h264_nvenc h264_omx h264_qsv h264_v4l2m2m h264_vaapi nvenc nvenc_h264 )

  


  


  but

  


  cv2.VideoWriter_fourcc(*"h264")


  


  results in :

  


  


  OpenCV : FFMPEG : tag 0x34363268/'h264' is not supported with codec id 27 and format 'mp4 / MP4 (MPEG-4 Part 14)'

  


  


  I could not find online what was wrong (h264 is not installed, how to install it ? the 'fourcc' of h264 is not 'h264' ? I should not create a *.mp4 file ?)

  


• avutil/aes : Don't use misaligned pointers

  21 octobre 2022, par Andreas Rheinhardt

  avutil/aes : Don't use misaligned pointers
  The AES code uses av_aes_block, a union consisting of
  
  uint64_t[2], uint32_t[4], uint8_t[4][4] and uint8_t[16].
  
  subshift() performs byte-wise manipulations of two av_aes_blocks,
  
  but when encrypting, it does so with a shift of two bytes ;
  
  more precisely, it uses
  
  "av_aes_block *s1 = (av_aes_block *) (s0[0].u8 - s)"
  
  and lateron uses the uint8_t[16] member to access s0.
  
  Yet av_aes_block requires to be suitably aligned for
  
  the uint64_t[2] member, which s0[0].u8 - 2 is certainly
  
  not. This is in violation of 6.3.2.3 (7) of C11. UBSan
  
  reports this in the aes_ctr, mov-3elist-encrypted,
  
  mov-frag-encrypted, mov-tenc-only-encrypted and srtp
  
  tests.
  
  Furthermore, there is another issue here : The pointer points
  
  outside of s0 ; this works, because all the accesses lateron
  
  use an index >= 3. (Clang-)UBSan reports this as
  
  "runtime error : index -2 out of bounds for type 'uint8_t[16]'".
  This commit fixes both of these issues : The latter issue
  
  is fixed by applying an offset of "+ 3" during the cast
  
  and subtracting this from the indices used lateron.
  
  The former issue is solved by not casting to av_aes_block*
  
  at all ; instead simply cast to unsigned char*.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavutil/aes.c