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• c++, FFMPEG, H264, creating zero-delay stream

  5 février 2015, par Mat

  I’m trying to encode video (using h264 codec at the moment, but other codecs would be fine too if better suited for my needs) such that the data needed for decoding is available directly after a frame (including the first frame) was encoded (so, i want only I and P frames, no B frames).

  How do I need to setup the AVCodecContext to get such a stream ? So far my testing arround with the values still always resulted in avcodec_encode_video() returning 0 on the first frame.

  //edit : this is currently my setup code of the AVCodecContext :

  static AVStream* add_video_stream(AVFormatContext *oc, enum CodecID codec_id, int w, int h, int fps)
  
  {
  
      AVCodecContext *c;
  
      AVStream *st;
  
      AVCodec *codec;
  
  
  
      /* find the video encoder */
  
      codec = avcodec_find_encoder(codec_id);
  
      if (!codec) {
  
          fprintf(stderr, "codec not found\n");
  
          exit(1);
  
      }
  
  
  
      st = avformat_new_stream(oc, codec);
  
      if (!st) {
  
          fprintf(stderr, "Could not alloc stream\n");
  
          exit(1);
  
      }
  
  
  
      c = st->codec;
  
  
  
      /* Put sample parameters. */
  
      c->bit_rate = 400000;
  
      /* Resolution must be a multiple of two. */
  
      c->width    = w;
  
      c->height   = h;
  
      /* timebase: This is the fundamental unit of time (in seconds) in terms
  
       * of which frame timestamps are represented. For fixed-fps content,
  
       * timebase should be 1/framerate and timestamp increments should be
  
       * identical to 1. */
  
      c->time_base.den = fps;
  
      c->time_base.num = 1;
  
      c->gop_size      = 12; /* emit one intra frame every twelve frames at most */
  
  
  
      c->codec = codec;
  
      c->codec_type = AVMEDIA_TYPE_VIDEO;
  
      c->coder_type = FF_CODER_TYPE_VLC;
  
      c->me_method = 7; //motion estimation algorithm
  
      c->me_subpel_quality = 4;
  
      c->delay = 0; 
  
      c->max_b_frames = 0; 
  
      c->thread_count = 1; // more than one threads seem to increase delay
  
      c->refs = 3;
  
  
  
      c->pix_fmt       = PIX_FMT_YUV420P;
  
  
  
      /* Some formats want stream headers to be separate. */
  
      if (oc->oformat->flags & AVFMT_GLOBALHEADER)
  
          c->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      return st;
  
  }

  but with this avcodec_encode_video() will buffer 13 frames before returning any bytes (after that, it will return bytes on every frame). if I set gop_size to 0, then avcodec_encode_video() will return bytes only after the second frame was passed to it. I need a zero delay though.

  This guy apparently was successful (even with larger gop) : http://mailman.videolan.org/pipermail/x264-devel/2009-May/005880.html but I don’t see what he is doing differently

• Trying to compile x264 and ffmpeg for iPhone - "missing required architecture arm in file"

  11 février 2013, par jtrim

  I'm trying to compile x264 for use in an iPhone application. I see there are instructions on how to compile ffmpeg for use on the platform here : http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2009-October/076618.html , but I can't seem to find anything this complete for compiling x264 on the iPhone. I've found this source tree : http://gitorious.org/x264-arm that seems to have support for the ARM platform.

  Here is my config line :

  ./configure —cross-prefix=/usr/bin/ —host=arm-apple-darwin10 —extra-cflags="-B /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk/usr/lib/ -I /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk/usr/lib/"
  

  ...and inside configure I'm using the gas-preprocessor script (first link above) as my assembler :

  gas-preprocessor.pl gcc
  

  When I start compiling, it chunks away for a little while, then it spits out these warnings and a huge list of undefined symbols :

  ld : warning : option -s is obsolete and being ignored
  ld : warning : -force_cpusubtype_ALL will become unsupported for ARM architectures
  ld : warning : in /usr/lib/crt1.o, missing required architecture arm in file
  ld : warning : in /usr/X11R6/lib/libX11.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libm.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libpthread.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libgcc_s.1.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libSystem.dylib, missing required architecture arm in file
  Undefined symbols :
  

  My guess would be that the problem has to do with the "missing required architecture arm in file" warning...any ideas ?

• Trying to compile x264 and ffmpeg for iPhone - "missing required architecture arm in file"

  4 août 2012, par jtrim

  I'm trying to compile x264 for use in an iPhone application. I see there are instructions on how to compile ffmpeg for use on the platform here : http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2009-October/076618.html , but I can't seem to find anything this complete for compiling x264 on the iPhone. I've found this source tree : http://gitorious.org/x264-arm that seems to have support for the ARM platform.

  Here is my config line :

  ./configure —cross-prefix=/usr/bin/ —host=arm-apple-darwin10 —extra-cflags="-B /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk/usr/lib/ -I /Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.2.sdk/usr/lib/"
  

  ...and inside configure I'm using the gas-preprocessor script (first link above) as my assembler :

  gas-preprocessor.pl gcc
  

  When I start compiling, it chunks away for a little while, then it spits out these warnings and a huge list of undefined symbols :

  ld : warning : option -s is obsolete and being ignored
  ld : warning : -force_cpusubtype_ALL will become unsupported for ARM architectures
  ld : warning : in /usr/lib/crt1.o, missing required architecture arm in file
  ld : warning : in /usr/X11R6/lib/libX11.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libm.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libpthread.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libgcc_s.1.dylib, missing required architecture arm in file
  ld : warning : in /usr/lib/libSystem.dylib, missing required architecture arm in file
  Undefined symbols :
  

  My guess would be that the problem has to do with the "missing required architecture arm in file" warning...any ideas ?