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• FFMPEG and libavfilter

  21 mars 2012, par Sergio

  With the currently installed ffmpeg I can't post watermark on converted videos. Can the reason for that be that I have not installed libavfilter library ?

  Currently # ffmpeg -v looks like :

  FFmpeg version SVN-r20374, Copyright (c) 2000-2009 Fabrice Bellard, et al.
  
  built on Oct 26 2009 22:47:01 with gcc 4.1.2 20080704 (Red Hat 4.1.2-46)
  
  configuration: --enable-libmp3lame --enable-libopencore-amrnb --enable-version3 -   enable-libopencore-amrwb --enable-version3 --enable-nonfree --enable-libfaad --enable-gpl - -disable-mmx --enable-shared --enable-libfaac --enable-libvorbis
  
  libavutil     50. 3. 0 / 50. 3. 0
  
  libavcodec    52.37. 1 / 52.37. 1
  
  libavformat   52.39. 2 / 52.39. 2
  
  libavdevice   52. 2. 0 / 52. 2. 0

  As you can see I'm missing libavfilter ? How can I add that library to FFMPEG and successfully add watermark on videos ?

  Thanks for any help.

• 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

• Why is ffmpeg executable so much faster than using libfdk_aac directly ?

  3 février 2016, par lancejabr

  When I encode a wav file to AAC using the ffmpeg executable (using libfdk_aac and setting -threads 1), the process completes several times faster than when I use the AAC encoding example provided by the libfdk_aac library itself. I looked at the code and the central loop in libfdk_aac is almost identical to the aac_encode_frame method in the ffmpeg source.

  Anyone know why the executable would be so much faster ? I’m looking into compilation options but we’re talking like 8x speedup so I don’t think it’s just putting -O3 on there... Does ffmpeg encode multiple buffers at once even when there is only one thread ?