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• Although ffmpeg installed, unable to save mp4 file on disk

  2 janvier 2020, par yannis

  Although I have installed ffmpeg, matplotlib reports that MovieWriter ffmpeg is unavailable and the MP4 file created is empty.

  import numpy as np
  
  from matplotlib import pyplot as plt
  
  from matplotlib import animation
  
  
  
  # First set up the figure, the axis, and the plot element we want to animate
  
  fig = plt.figure()
  
  ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
  
  line, = ax.plot([], [], lw=2)
  
  
  
  # initialization function: plot the background of each frame
  
  def init():
  
      line.set_data([], [])
  
      return line,
  
  
  
  # animation function.  This is called sequentially
  
  def animate(i):
  
      x = np.linspace(0, 2, 1000)
  
      y = np.sin(2 * np.pi * (x - 0.01 * i))
  
      line.set_data(x, y)
  
      return line,
  
  
  
  # call the animator.  blit=True means only re-draw the parts that have changed.
  
  anim = animation.FuncAnimation(fig, animate, init_func=init,
  
                                 frames=200, interval=20, blit=True)
  
  
  
  # save the animation as an mp4.  This requires ffmpeg or mencoder to be
  
  # installed.  The extra_args ensure that the x264 codec is used, so that
  
  # the video can be embedded in html5.  You may need to adjust this for
  
  # your system: for more information, see
  
  # http://matplotlib.sourceforge.net/api/animation_api.html
  
  anim.save('basic_animation.mp4', fps=30, extra_args=['-vcodec', 'libx264'])
  
  
  
  plt.show()

  I have even added the line plt.switch_backend('TkAgg') proposed in another post, nothing changed. Here is my matplotlib :

  Name: matplotlib
  
  Version: 2.1.0
  
  Summary: Python plotting package
  
  Home-page: http://matplotlib.org

  my ffmpeg :

  Name: ffmpeg
  
  Version: 1.4
  
  Summary: ffmpeg python package url [https://github.com/jiashaokun/ffmpeg]
  
  Home-page: https://github.com/jiashaokun/ffmpeg

  and my Python version :

  Python 3.6.5

  The error I get is :

  /usr/local/lib/python3.6/site-packages/matplotlib/animation.py:1218: UserWarning: MovieWriter ffmpeg unavailable
  
    warnings.warn("MovieWriter %s unavailable" % writer)

  This error has been reported many times on stackoverflow, each time the solution is either to install ffmpeg (mine is installed) or to add that extra line about the backend, which hasn’t changed anything for me.

  Curiously enough the plt.show()command works and I do preview an animation, but the only file format to save it is (nonanimated) PNG.

• convert pcm stream data to encoded aac data

  24 décembre 2019, par Kumar

  I tried to convert pulse-audio pcm stream data to aac encoded data using ffmpeg.
  But after encoding I get noise-full data, not the correct one. Here I post my code, anyone help me with some ideas.

  Initial configuration :

      av_register_all();
  
  
  
      int error;
  
      if ((error = avio_open(&output_io_context,"out.aac",AVIO_FLAG_WRITE))<0) {
  
              printf("could not open output file\n");
  
      }
  
  
  
      if (!(output_format_context = avformat_alloc_context())) {
  
              printf("output_format_context error\n");
  
      }
  
  
  
      output_format_context->pb = output_io_context;
  
  
  
      if(!(output_format_context->oformat = av_guess_format(NULL, "out.aac", NULL))) {
  
              printf("guess format error\n");
  
      }
  
  
  
      codec = avcodec_find_encoder(AV_CODEC_ID_AAC);
  
      if (codec == NULL) {
  
              printf("avcodec_find_encoder: ERROR\n");
  
      }
  
  
  
      if (!(stream = avformat_new_stream(output_format_context, NULL))) {
  
              printf("stream create error\n");
  
      }
  
      output_codec_context = avcodec_alloc_context3(codec);
  
      if(!output_codec_context) {
  
              printf("output_codec_context is null\n");
  
      }
  
  
  
      output_codec_context->channels       = CHANNELS;
  
      output_codec_context->channel_layout = av_get_default_channel_layout(CHANNELS);
  
      output_codec_context->sample_rate    = SAMPLE_RATE; //input_codec_context->sample_rate;
  
      output_codec_context->sample_fmt     = codec->sample_fmts[0];
  
      output_codec_context->bit_rate       = 48000; //OUTPUT_BIT_RATE;
  
  
  
      stream->time_base.den = SAMPLE_RATE;//input_codec_context->sample_rate;
  
      stream->time_base.num = 1;
  
  
  
      if(output_format_context->oformat->flags & AVFMT_GLOBALHEADER)
  
              output_codec_context->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
  
  
  
      if ((error = avcodec_open2(output_codec_context, codec, NULL)) < 0) {
  
          printf("error");
  
      }
  
  
  
      error = avcodec_parameters_from_context(stream->codecpar, output_codec_context);
  
  
  
      if (write_output_file_header(output_format_context)) {
  
              printf("write header failure...\n");
  
      }

  Data encoding :

  AVFrame *output_frame;
  
  int frame_pos = 0, ctx_frame_size = output_codec_context->frame_size;
  
  int size = av_samples_get_buffer_size(NULL, CHANNELS,
  
                output_codec_context->frame_size,output_codec_context->sample_fmt, 1);
  
  if((x =  avcodec_fill_audio_frame(output_frame, CHANNELS,
  
                 output_codec_context->sample_fmt, data, length, 1)) < 0) {
  
        printf("avcodec_fill_audio_frame error : %s\n", av_err2str(x));
  
  }
  
  
  
   int data_written;
  
   if (encode_audio_frame(output_frame, output_format_context,
  
              output_codec_context, &data_written)) {
  
          printf("encode_audio_frame error\n");
  
    }
  
  
  
    av_frame_free(&output_frame);

  helper_function :

   int encode_audio_frame(AVFrame *frame,AVFormatContext *output_format_context,
  
                AVCodecContext *output_codec_context, int *data_present)
  
   {
  
     AVPacket output_packet;
  
     int error;
  
     init_packet(&output_packet);
  
  
  
     if (frame) {
  
        frame->pts = pts;
  
        pts += frame->nb_samples;
  
     }
  
  
  
     error = avcodec_send_frame(output_codec_context, frame);
  
     if (error == AVERROR_EOF) {
  
       error = 0;
  
       goto cleanup;
  
     } else if (error < 0) {
  
        fprintf(stderr, "Could not send packet for encoding (error '%s')\n",
  
              av_err2str(error));
  
        return error;
  
     }
  
  
  
     error = avcodec_receive_packet(output_codec_context, &output_packet);
  
     if (error == AVERROR(EAGAIN)) {
  
       error = 0;
  
       goto cleanup;
  
     } else if (error == AVERROR_EOF) {
  
        error = 0;
  
        goto cleanup;
  
     } else if (error < 0) {
  
        fprintf(stderr, "Could not encode frame (error '%s')\n",
  
              av_err2str(error));
  
        goto cleanup;
  
     } else {
  
        *data_present = 1;
  
    }
  
  
  
    if (*data_present &&
  
        (error = av_write_frame(output_format_context, &output_packet)) < 0) {
  
        fprintf(stderr, "Could not write frame (error '%s')\n",
  
               av_err2str(error));
  
        goto cleanup;
  
    }
  
  
  
    cleanup:
  
        av_packet_unref(&output_packet);
  
        return error;
  
   }

  • Do we need to fill AVFrame with sizeof(av_samples_get_buffer_size) or context->frame_size ?
    

  TYIA :) !!

• vp9lpf/x86 : save one register in loopfilter surface coverage.

  20 décembre 2014, par Ronald S. Bultje

  vp9lpf/x86 : save one register in loopfilter surface coverage.
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DBH] libavcodec/x86/vp9lpf.asm