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• FFmpeg cross compile for Android fails with on C compiler test for x86_64

  5 novembre 2018, par nLL

  I am trying to cross compile FFmpeg for Android with NDK r16b
  I have manged to compile without any issues for all platforms but x86_64.

  Here is my compile script

          #!/bin/bash
  
  
  
  
  
  
  
      function build_one
  
      {
  
      ./configure \
  
      --prefix=$PREFIX \
  
      --enable-shared \
  
      --disable-static \
  
      --enable-pic \
  
      --enable-small \
  
      --disable-programs \
  
      --disable-symver \
  
      --target-os=android \
  
      --enable-cross-compile \
  
      --cross-prefix=$CROSS_PREFIX \
  
      --extra-cflags="-Os -fpic $ADDI_CFLAGS" \
  
      --extra-ldflags="$ADDI_LDFLAGS" \
  
      --sysroot=$TOOLCHAIN/sysroot $ADDITIONAL_CONFIG_FLAG \
  
      --disable-all --disable-autodetect --disable-network --enable-pthreads \
  
      --enable-protocol=file --enable-protocol=pipe --enable-protocol=concat \
  
      --disable-all --disable-autodetect --disable-network --enable-pthreads \
  
      --enable-avcodec --enable-avformat --enable-swresample --enable-avfilter --enable-filter=aresample \
  
      --enable-parser=aac --enable-parser=aac_latm --enable-parser=flac --enable-parser=mpegaudio --enable-parser=vorbis \
  
      --enable-muxer=mp3,wav --enable-encoder=pcm*,libmp3lame --enable-nonfree --enable-gpl \
  
      --enable-jni --enable-mediacodec --enable-libmp3lame
  
  
  
  
  
      make -j4
  
      make install
  
      make distclean
  
      }
  
  
  
      HOME_PATH=/home/nll/Desktop
  
      CPU=x86_64
  
      TOOLCHAIN=$HOME_PATH/my_toolchains/x86_64
  
      CROSS_PREFIX=$TOOLCHAIN/bin/x86_64-linux-android-
  
      mkdir -p $(pwd)/android/$CPU
  
      PREFIX=$(pwd)/android/$CPU
  
      ADDI_CFLAGS="-march=x86-64 -I$INCLUDE_PATH"
  
      ADDI_LDFLAGS="-shared -L$LIBS_PATH"
  
      ADDITIONAL_CONFIG_FLAG="--arch=x86_64 --enable-x86asm"
  
      build_one

  Above script fails with

          WARNING: /home/nll/Desktop/my_toolchains/x86_64/bin/x86_64-linux-android-pkg-config not found, library detection may fail.
  
      mktemp -u XXXXXX
  
      5ZpQya
  
      test_ld cc
  
      test_cc
  
      BEGIN /tmp/ffconf.KWqViHoN/test.c
  
          1   int main(void){ return 0; }
  
      END /tmp/ffconf.KWqViHoN/test.c
  
      /home/nll/Desktop/my_toolchains/x86_64/bin/x86_64-linux-android-gcc --sysroot=/home/nll/Desktop/my_toolchains/x86_64/sysroot -Os -fpic -march=x86-64 -I -c -o /tmp/ffconf.KWqViHoN/test.o /tmp/ffconf.KWqViHoN/test.c
  
      /home/nll/Desktop/my_toolchains/x86_64/bin/x86_64-linux-android-gcc -shared -L --sysroot=/home/nll/Desktop/my_toolchains/x86_64/sysroot -o /tmp/ffconf.KWqViHoN/test /tmp/ffconf.KWqViHoN/test.o
  
      /home/nll/Desktop/my_toolchains/x86_64/bin/../lib/gcc/x86_64-linux-android/4.9.x/../../../../x86_64-linux-android/bin/ld: error: /tmp/ffconf.KWqViHoN/test.o: unsupported ELF file type 2
  
      collect2: error: ld returned 1 exit status
  
      C compiler test failed.

  So, error is "unsupported ELF file type 2" which means 64 bit. But, I am trying to build 64 bit library anyway.

  I do not understand what is the issue here. Can anyone give me some direction ?

• How to use ffmpeg in JavaScript to decode H.264 frames into RGB frames

  17 juin 2020, par noel

  I'm trying to compile ffmpeg into javascript so that I can decode H.264 video streams using node. The streams are H.264 frames packed into RTP NALUs so any solution has to be able to accept H.264 frames rather than a whole file name. These frames can't be in a container like MP4 or AVI because then the demuxer needs to needs the timestamp of every frame before demuxing can occur, but I'm dealing with a real time stream, no containers.

  



  Streaming H.264 over RTP

  



  Below is the basic code I'm using to listen on a udp socket. Inside the 'message' callback the data packet is an RTP datagram. The data portion of the data gram is an H.264 frame (P-frames and I-frames).

  



  var PORT = 33333;
var HOST = '127.0.0.1';

var dgram = require('dgram');
var server = dgram.createSocket('udp4');

server.on('listening', function () {
    var address = server.address();
    console.log('UDP Server listening on ' + address.address + ":" + address.port);
});

server.on('message', function (message, remote) {
    console.log(remote.address + ':' + remote.port +' - ' + message);
    frame = parse_rtp(message);

    rgb_frame = some_library.decode_h264(frame); // This is what I need.

});

server.bind(PORT, HOST);  


  



  I found the Broadway.js library, but I couldn't get it working and it doesn't handle P-frames which I need. I also found ffmpeg.js, but could get that to work and it needs a whole file not a stream. Likewise, fluent-ffmpeg doesn't appear to support file streams ; all of the examples show a filename being passed to the constructor. So I decided to write my own API.

  



  My current solution attempt

  



  I have been able to compile ffmpeg into one big js file, but I can't use it like that. I want to write an API around ffmpeg and then expose those functions to JS. So it seems to me like I need to do the following :

  



  

  1. Compile ffmpeg components (avcodec, avutil, etc.) into llvm bitcode.

  


  2. Write a C wrapper that exposes the decoding functionality and uses EMSCRIPTEN_KEEPALIVE.

  


  3. Use emcc to compile the wrapper and link it to the bitcode created in step 1.

  


  



  I found WASM+ffmpeg, but it's in Chinese and some of the steps aren't clear. In particular there is this step :

  



  emcc web.c process.c ../lib/libavformat.bc ../lib/libavcodec.bc ../lib/libswscale.bc ../lib/libswresample.bc ../lib/libavutil.bc \


  



   :( Where I think I'm stuck

  



  I don't understand how all the ffmpeg components get compiled into separate *.bc files. I followed the emmake commands in that article and I end up with one big .bc file.

  



  2 questions

  



  1. Does anyone know the steps to compile ffmpeg using emscripten so that I can expose some API to javascript ?
  
 2. Is there a better way (with decent documentation/examples) to decode h264 video streams using node ?

  


• use OpenCV to capture a good frame of faces from IP camera [on hold]

  17 octobre 2018, par wiwengweng

  everyone. I am working on some research about getting frames from IP camera, and then detect and recognize faces. There is some implements on the last two steps. And my first problem is to judge if a frame with faces is good enough for detection. Video stream is read by OpenCV and/or ffmpeg, and there are many ways to capture frames one by one.

  As we know, people are always walking through, so frames captured from IP camera is not always good. But the good news is the if we extract the frames from the IP camera video file, we find some frames good enough for detection.

  is it possible to analyse by using the opencv CascadeClassifier to detect if the face is clear or not ? Right now I just use minSize and maxSize to capture the face, however I cannot judge if it is clear.

  I also try de-blurring pictures of frames using GAN, but that will need more time, so I think that is not an ideal way. So any advice is welcome.