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• FFMPEG MemoryAccessException on cleanup

  16 décembre 2015, par Casey Price

  I’ve written an application that records from various USB webcams using ffmpeg, however if I unplug a camera while ffmpeg is in the middle of recording I get memory access exceptions when running the following cleanup code.

  if (packet.data != 0)
  
      av_packet_unref(&packet);
  
  
  
  if (frame != 0)
  
      av_frame_free(&frame);
  
  
  
  
  
  if (ifmt_ctx != NULL)
  
  {
  
      for (i = 0; i < ifmt_ctx->nb_streams; i++) {
  
          avcodec_close(ifmt_ctx->streams[i]->codec);
  
          if (ofmt_ctx && ofmt_ctx->nb_streams > i && ofmt_ctx->streams[i] && ofmt_ctx->streams[i]->codec)
  
              avcodec_close(ofmt_ctx->streams[i]->codec);
  
          if (filter_ctx && filter_ctx[i].filter_graph)
  
              avfilter_graph_free(&filter_ctx[i].filter_graph);
  
      }
  
  }
  
  
  
  if (filter_ctx != NULL && filter_ctx->buffersink_ctx != NULL && filter_ctx->buffersrc_ctx != NULL && filter_ctx->filter_graph != NULL)
  
      av_freep(&filter_ctx);
  
  
  
  if (ifmt_ctx != 0)
  
      avformat_close_input(&ifmt_ctx);
  
  
  
  if (ofmt_ctx && ofmt_ctx->oformat != NULL && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE))
  
      avio_closep(&ofmt_ctx->pb);
  
  
  
  if (ofmt_ctx != 0 && ofmt_ctx->oformat != 0)
  
      avformat_free_context(ofmt_ctx);

  Specifically it crashes on

  if (filter_ctx != NULL && filter_ctx->buffersink_ctx != NULL && filter_ctx->buffersrc_ctx != NULL && filter_ctx->filter_graph != NULL)
  
          av_freep(&filter_ctx);

  With a Null Reference exception on the if check sometimes. Other times the code runs fine and doesn’t crash. I’ve also tried

  if (filter_ctx)
  
      av_free(filter_ctx);

  But this gives me a MemoryAccessException instead of a null reference, I’m guessing something on another thread is changing my data while cleaning up, however all of my variables are are not shared with any other thread.

  Does anyone know whats going on ?

• ffmpeg record screen file formats

  3 avril 2020, par New_Dev

  Good day,
I'm currently writing a bash script which records the screen under certain conditions. The problem is that only avi works as a file extension for recording the screen. This script is going to be used on an Raspberry Pi and currently I get on a decent virtual machine only 10-20 fps (goal would be around 30 fps). I think .avi is not suited for my project. But .mpeg and .mp4 are not working for recording. I tried recording with .avi and then converting it in .mp4, but I have limited memory and .avi ist just too big in size. I use currently the following command :

  



  ffmpeg -f x11grab -y -r 30 -s 960x750 -i :0.0+0,100 -vcodec huffyuv ./Videos/out_$now.avi
//$now is the current date and time


  



  So I wanted to know if I need some special packages from ffmpeg to record with for example .mp4 or if there are other file formats available for ffmpeg screen recording.

  



  Edit :
I found that the codec libx264 for mp4 works, but the fps drop until they hit5 fps, which is definetly too low. The recorded video appeared like being a fast forward version of the recorded screen.

  



  With mpeg4 for mpeg I reached over 30 fps, but the video qualitywas very bad.

  



  It appears that even my big avi-files look like being played fast forward. Is there something I do wrong ?

  



  Is there a good middle way, where I get a decend video quality, good fps (20+) and a file which isn't too big ?

  



  Edit 2 :
I tried recording it with .avi and converting it afterwards. Just converting with ffmpeg -i test.avi -c:a aac -b:a 128k -c:v libx264 -crf 23 output.mp4 
resulted in the same framedrops as if I was recording with .mp4. But when I cut a littlebit of the beginning of the video and named the outputfile .mp4, the size became much smaller. But when I started the cutting at 0:00:00 (so tried just converting), it just changed the file format without converting it (so the size stayed the same). Any ideas ?

  


• x264 Building error - Android

  21 avril 2016, par Jay Parikh

  I am using this repository to build ffmpeg static library which includes x264,libpng and others, please
  visit this link https://github.com/writingminds/ffmpeg-android

  i am using windows 7 as host and ubuntu 15.10 (_64) as guest os using VMware Workstation 12
  and
  Android-ndk-r11b-linux-x86_64

  i do have Prebuilt libraries , but now i want it without PIE support

  i am getting this error in config.log in x264 folder while building
  through

  ./android_build.sh

  here is the log :

  x264 configure script
  
  Command line options: "--cross-prefix=/mnt/hgfs/uShare/ffmpeg-android/toolchain-android/bin/arm-linux 
  
  /mnt/hgfs/uShare/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi-gcc 
  
  
  
  checking whether /mnt/hgfs/uShare/ffmpeg-android/toolchain-android/bin/arm-linux-androideabi-gcc 
  
  
  
  --sysroot=/mnt/hgfs/uShare/ffmpeg-android/toolchain-android/sysroot works... no
  
  
  
   Failed commandline was:
  
  
  
  --sysroot=/mnt/hgfs/uShare/ffmpeg-android/toolchain-android/sysroot conftest.c  -Wall -I. -I$(SRCPATH) --sysroot=/mnt/hgfs/uShare/ffmpeg-android/toolchain-android/sysroot    --sysroot=/mnt/hgfs/uShare/ffmpeg-android/toolchain-android/sysroot -lm -o conftest
  
  
  
  /mnt/hgfs/uShare/ffmpeg-android/toolchain-android/bin/../lib/gcc/arm-linux-androideabi/4.9/../../../../arm-linux-androideabi/bin/ld: fatal error:
  
  
  
  conftest: Input/output error
  
  
  
  Failed program was: 
  
  
  
  int main (void) {  return 0; }
  
  
  
  DIED: No working C compiler found.

  ushare is my shared folder between windows and ubuntu

  I have spend almost a week ,trying to solve every error i get.
  these errors are like never ending , 1 solution give 10 more errors
  i have researched a LOT for this library

  thanks a lot in advance.

  Also i thought that x264 library might have poroblem ,so i tried to disable it
  but next library "libpng" also had Same log Error

  i think problem is in Input/output error (obviously)
  this line in log kind of confuses me (those /../../)

  /mnt/hgfs/uShare/ffmpeg-android/toolchain-android/bin/../lib/gcc/arm-linux-androideabi/4.9/../../../../arm-linux-androideabi/bin/ld : fatal error :

  its like two folder overlaping address...

  thanks a lot in advance.
  please don’t go harsh on me ,its my first time,all thanks to this thing...