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• ffmpeg libx264 neon optimization breaks execution

  27 janvier 2014, par nmxprime

  Hi use libx264 source obtained from x264-snapshot-20140122-2245 and compiling using below script

  NDK=~/Android/android-ndk-r7c
  
  PLATFORM=$NDK/platforms/android-9/arch-arm/
  
  PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
  
  function build_one
  
  {
  
  ./configure --prefix=$PREFIX \
  
  --sysroot=$PLATFORM \
  
  --disable-avs \
  
  --disable-lavf \
  
  --disable-ffms \
  
  --disable-gpac \
  
  --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
  
  --host=arm-linux \
  
  --enable-static \
  
  --libdir=$PLATFORM/usr/lib \
  
  --includedir=$PLATFORM/usr/include \
  
  --extra-cflags="-march=armv7-a -mfloat-abi=softfp -mfpu=neon -mvectorize-with-neon-quad" \
  
  --extra-ldflags="-Wl,--fix-cortex-a8" \
  
  --enable-debug

  The config log is :

  platform:      ARM
  
  system:        LINUX
  
  cli:           yes
  
  libx264:       internal
  
  shared:        no
  
  static:        yes
  
  asm:           yes
  
  interlaced:    yes
  
  avs:           no
  
  lavf:          no
  
  ffms:          no
  
  mp4:           no
  
  gpl:           yes
  
  thread:        no
  
  opencl:        yes
  
  filters:       crop select_every
  
  debug:         yes
  
  gprof:         no
  
  strip:         no
  
  PIC:           no
  
  bit depth:     8
  
  chroma format: all
  
  
  
  You can run 'make' or 'make fprofiled' now.

  I hope the above code compiles and optimizes for NEON execution

  Doubts :

  Why Threads is no, because i didn't specified --disable-thread

  What is cli and it's significance here, also significance of opencl, such that libx264 uses opencl features ?

  ---

  Then i built ffmpeg 1.2.5with following script

  ./configure --target-os=linux \
  
  --prefix=$PREFIX \
  
  --enable-cross-compile \
  
  --extra-libs="-lgcc" \
  
  --arch=arm \
  
  --cc=$PREBUILT/bin/arm-linux-androideabi-gcc \
  
  --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
  
  --nm=$PREBUILT/bin/arm-linux-androideabi-nm \
  
  --sysroot=$PLATFORM \
  
  --extra-cflags=" -O3 -fpic -DANDROID -DHAVE_SYS_UIO_H=1 -Dipv6mr_interface=ipv6mr_ifindex -fasm -Wno-psabi -fno-short-enums -fno-strict-aliasing -finline-limit=300 $OPTIMIZE_CFLAGS " \
  
  --disable-shared \
  
  --enable-static \
  
  --extra-ldflags="-Wl,-rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -nostdlib -lc -lm -ldl -llog -lx264 $EXTRA_LD_FLAG" \
  
  --disable-ffplay \
  
  --disable-everything \
  
  --enable-avformat \
  
  --enable-avcodec \
  
  --enable-libx264 \
  
  --enable-gpl \
  
  --enable-encoder=libx264 \
  
  --enable-encoder=libx264rgb \
  
  --enable-decoder=h264 \
  
  --disable-network \
  
  --disable-avfilter \
  
  --disable-avdevice \
  
  --enable-debug=3 \
  
  $ADDITIONAL_CONFIGURE_FLAG

  where

  ADDITIONAL_CONFIGURE_FLAG = --enable-debug=3
  
  OPTIMIZE_CFLAGS="-mfloat-abi=softfp -mfpu=neon -marm -march=$CPU -mvectorize-with-neon-quad"

  The log shows NEON supported.

  When i run the code (called in a while loop),

  ret = avcodec_encode_video2(c, &pkt, picture, &got_output);//avcodec_encode_video(c, finalout, outbuf_size, picture);
  
  
  
  fprintf(stderr,"ret = %d, got-out = %d \n",ret,got_output);
  
  if (ret < 0) 
  
          fprintf(stderr, "error encoding frame\n");
  
  
  
      if (got_output) 
  
          fprintf(stderr,"encoding frame %3d (size=%5d): (ret=%d)\n", 1, pkt.size,ret);

  it runs for 2 or 3 time(during which if(got_output) is not true), then i get SIGSEGV. Tried addr2line and ndk-stack but no use[Though i enabled debug info, ndk-stack cannot find routine info].

  I edited libx264's encoder.c code with some fprintf statements.
  Posting snippet of code

     if( h->frames.i_input <= h->frames.i_delay + 1 - h->i_thread_frames )
  
      {
  
          /* Nothing yet to encode, waiting for filling of buffers */
  
          pic_out->i_type = X264_TYPE_AUTO;
  
  fprintf(stderr,"EditLog:: Returns as waiting for filling \n"); //edit
  
          return 0;
  
      }
  
  }
  
  
  
  else
  
  {
  
      /* signal kills for lookahead thread */
  
      x264_pthread_mutex_lock( &h->lookahead->ifbuf.mutex );
  
      h->lookahead->b_exit_thread = 1;
  
      x264_pthread_cond_broadcast( &h->lookahead->ifbuf.cv_fill );
  
      x264_pthread_mutex_unlock( &h->lookahead->ifbuf.mutex );
  
  }
  
  fprintf(stderr,"After wait for fill \n");
  
  fprintf(stderr,"h: %p \n",h); //edit
  
  fprintf(stderr,"h->i_frame = %p \n",&h->i_frame); //edit
  
  h->i_frame++;
  
  fprintf(stderr,"after i_frame++");

  in log, i don't see after i_frame++, here occurs (may be) the SIGSEGV.

  Please help in solving it. The same works without neon optimization !!

• FFmpeg export specific pixels

  30 avril 2018, par Neros

  I’m looking for a way to extract a set of specific pixels from a video (and possibly store them in JSON)

  So far i have found FFmpeg which looks like it should do the heavy lifting if i can find the correct commands.

  Alternatively I could try using the source and building my own project that just leverages FFmpeg to extract frame data, but i think/hope that’s unnecessary.

  So if its possible, What commands could accomplish this ?

  Or perhapse there is a whole different approach i could take, any help would be great !

• playing multiple intervals of a video [on hold]

  6 juin 2018, par gagan singh

  I have a video. I know how to play one interval say 10s-20s.

  How do I play multiple intervals, say 10s-20s then immediately 30s-50s and so on ?

  I am also fine with running ffmpeg -c once to extract the combined stream of my time ranges.

  In one of the ffmpeg query, some one mentioned edit list support in some video players. What is that ?

  I am fine with playing the video with any linux video player, vlc, mplayer etc.
  anything which can play something like the following.

  player —intervals=10-20,30-50 video.mp4

  basically for a movie, I want to play selected intervals of the movie, instead of the whole movie.

  I hope this makes my question clearer.