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• How to discover framebuffer format on android ?

  18 mars 2013, par Guilherme Torres Castro

  i'm capturing framebuffer on my android device, but each device has a different frame buffer pixel format. How can i get the this format for each device ?

  I found i can get the bbp and screen resoution using :

  ioctl -rl 28 /dev/graphics/fb0 17920

  This command return :

  return buf : f0 00 00 00 40 01 00 00 f0 00 00 00 80 02 00 00 00 00 00 00 00 00 00 00 20 00 00 00

  In little-endian format i have :

  • The last four bytes (20) is the number of bbp 32.
  • The first four bytes is the screen width 0xF0 = 240
  • Bytes 5 to 8 is the screen height 0x0140 = 320

  I tried to decode the fb (Galaxy 5) using the folowing command :

  ./ffmpeg -vframes 1 -vcodec rawvideo -f rawvideo -pix_fmt rgb32 -s 240x320 -i fb0 -f image2 -vcodec png image%d.png

  And i got this warning :

  Invalid buffer size, packet size 40960 < expected length 307200 Error
  while decoding stream #0:0 : Invalid argument

  and this two images :

  
  

  I think what's is wrong is the pix_fmt param.

• avformat/matroskadec : Fix heap-buffer overflow upon gigantic timestamps

  25 août 2021, par Andreas Rheinhardt

  avformat/matroskadec : Fix heap-buffer overflow upon gigantic timestamps
  The WebM DASH Manifest demuxer creates a comma-delimited list of
  
  all the timestamps of index entries. It allocates 20 bytes per
  
  timestamp ; yet the largest 64bit numbers have 20 decimal digits
  
  (for int64_t it can be '-'+ 19 digits), so that one needs 21B
  
  per entry because of the comma (resp. the final NUL).
  The code uses snprintf, but snprintf returns the strlen of the string
  
  that would have been written had the supplied buffer been big enough.
  
  And if this is 21, then the next entry is written at an offset of 21
  
  from the current position. So if enough such entries exist, the buffer
  
  won't suffice.
  This commit fixes this by replacing the allocation of buffer for
  
  the supposedly worst-case with dynamic allocations by using an AVBPrint.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavformat/matroskadec.c

• FFmpeg library in WPF

  20 avril 2022, par MikeTMG

  I am building a softwere that can decode and encode using Wpf and c#, and I want to do that using, FFmpeg libary. I saw the ffmpeg autogen warpper but I couldn't find any documantion for its function.&#xA;Can someone please find me one ? Or better, give me better warrper.

  &#xA;&#xA;

  I already tried FFMpegCore, its working but very slow. For Exaple it takes 20 seconds to decode a specific frame.(And i have monstruos computer)&#xA;If will be happy if ou could give me better warpper, or a guide for ffmpeg.autogen.&#xA;Thanks in advance.

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