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• Capture CMOS video with FPGA, encode and send over Ethernet

  23 décembre 2015, par ya_urock

  I am planning a open source university project for my students based on Zynq Xilinx FPGA that will capture CMOS video, encode it into transport stream and send it over Ethernet to remote PC. Basically I want to design yet another IP camera. I have strong FPGA experience, but lack knowledge regarding encoding and transfering video data. Here is my plan :

  1. Connect CMOS camera to FPGA, recieve video frames and save them to external DDR memory, verify using HDMI output to monitor. I have no problems with that.

  2. I understand that I have to compress my video stream for example to H.264 format and put into transport stream. Here I have little knowledge and require some hints.

  3. After I form transport stream I can send it over network using UDP packets. I have working hardware solution that reads data from FIFO and sends it to remote PC as UDP papckets.

  4. And finally I plan to receive and play video using ffmpeg library.

     ffplay udp://localhost:5678

  My question is basically regarding 2 step. How do I convert pixel frames to transport stream ? My options are :

  1. Use commercial IP, like
     • http://www.xilinx.com/products/intellectual-property/1-4iso32.html
     • http://www.xilinx.com/products/intellectual-property/1-1lk9j1.html#overview

  Here I doubt that they are free to use and we don’t have much funds.

  2. Use open cores like

     • http://sourceforge.net/projects/hardh264/ - here core generates only h264 output, but how to encapsulate it into transport stream ?
     • I have searched opencores.org but with no success on this topic
     • Maybe somebody knows some good open source relevant FPGA projects ?

  3. Develop harware encoder by myself using Vivado HLS (C Language). But here is the problem that I don’t know the algorithm. Maybe I could gig ffmpeg or Cisco openh264 library and find there a function that converts raw pixel frames to H.264 format and then puts it into transport stream ? Any help would be appriciated here also.

  Also I am worried about format compatibility of stream I might generate inside FPGA and the one expected at host by ffplay utility. Any help, hints, links and books are appriciated !

• Unable to link against FFmpeg libaries

  28 octobre 2015, par Cody

  I tried to build this, but always got link-time error.

  #include <libavutil></libavutil>log.h>    
  
  int main(int argc, char *argv[])
  
  {
  
      ::av_log_set_flags(AV_LOG_SKIP_REPEATED);
  
      return 0;
  
  }

  My distro is Debian GNU/Linux 8 (jessie). The FFmpeg was built by myself, and the configure command was...

  $ ./configure --prefix=/usr/local --disable-static --enable-shared \
  
  > --extra-ldflags='-Wl,-rpath=/usr/local/lib'

  The link-error is as follows.

  $ g++ foo.cpp -D__STDC_CONSTANT_MACROS -Wall \
  
  > -Wl,-rpath=/usr/local/lib \
  
  > $(pkg-config --cflags --libs libavutil)
  
  /tmp/ccKzgEFb.o: In function `main':
  
  foo.cpp:(.text+0x17): undefined reference to `av_log_set_flags(int)'
  
  collect2: error: ld returned 1 exit status

  where the output of pkg-config is...

  $ pkg-config --cflags --libs libavutil
  
  -I/usr/local/include -L/usr/local/lib -lavutil

  The objdump shows that the shared object libavutil.so does have av_log_set_flogs inside.

  $ objdump --dynamic-syms /usr/local/lib/libavutil.so | grep 'av_log_set_flags'
  
  000260f0 g    DF .text  0000000a  LIBAVUTIL_54 av_log_set_flags

  Please note that the g++ command used to build the above application had a linker option -Wl,-rpath=/usr/local/lib, though it still doesn’t work. Also, I’ve tried to monitor with inotifywait if the other version provided by the distro were called. They were not, and the one being opened during execution of g++ was /usr/local/lib/libavutil.so.

  Summary :

  1. /usr/local/lib/libavutil.so does have the symbol.

  2. -rpath was used to force to link against the shared library.

  3. Why link-time error ? T_T

  Any suggestion or information would be highly appreciated ! Thanks !

  REEDIT : ffplay works fine and ldd shows it use /usr/local/lib/libavutil.so. So, the libraries seems not broken, and the problem becomes how to build my own codes to use the libraries.

• Use Windows ffmpeg to record audio output without using the StereoMix

  2 septembre 2016, par DevtelSoftware

  I am looking for a way to record the audio output (speakers) using Windows ffmpeg.
  I need to do this WITHOUT installing any extra dshow filters and without having the StereoMix input enabled (since this is not available on many computers).

  I have read in the ffmpeg documentation that the -map would allow redirecting an audio output so that ffmpeg sees it as an audio input but I can’t find any example of how to do that.

  In Linux I managed to do it like this :

  ffmpeg -f pulse -ac 2 -ar 44100 -i alsa_output.pci-0000_00_1f.4.analog-stereo.monitor -f pulse -ac 2 -ar 44100 -i alsa_input.pci-0000_00_1f.4.analog-stereo -filter_complex amix=inputs=2 test.mp4

  However I can’t find a similar way to do it in Windows and MacOSX.

  So in short, is it possible with the Windows ffmpeg to record audio from the speakers without extra dshow filters (out-of-the-box) ? Same question goes for MacOSX.

  Thanks !