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• Piping output of youtube-dl to a script using ffmpeg looks ok using echo but returns an error when executing

  22 février 2016, par user556068

  I am trying to use youtube-dl to get the urls of some videos and then pipe the resulting urls into the input of my script. So in my terminal I do

  youtube-dl --ignore-config -iga ~/Desktop/youtube/videolist.txt | myscript.sh

  In my script I define things as

  command='ffmpeg'        
  
  inputArgs='-i'              
  
  outputArgs='-c:v libx264 -preset ultrafast -qp 0'       
  
  directory="${HOME}/Desktop/Videos/"
  
  output="video${count}"      
  
  extension='mp4'         

  I test it with echo to make sure everything appears in the correct order.

  echo "${command}" "${inputArgs}" "${input}" "${outputArgs}" \
  
  "${directory}""${output}${count}"."${extension}"

  And the output from that looks correct. But when I try to run the same thing without the preceding echo command, i.e.,

  "${command}" "${inputArgs}" "${input}" "${outputArgs}" \
  
  "${directory}""${output}${count}"."${extension}"

  I get an error message that says

  At least one output file must be specified.

  So it seems pretty obvious to me that I’m doing something wrong when attempting to execute it.

  I have tried :

  • quoting the entire line as a whole
  • quoting different sections together
  • using the exec command in front of everything

  No matter what I do, an error occurs at some point in the process. I know it’s something simple I’m doing wrong. Would someone please enlighten me as to what that might be ?

  I feel very strongly that the . shouldn’t just be in the middle of everything like that, but I really don’t know.

  Again, everything looks as it should when I run echo before the string of shell parameters.

  If more of the script I’m using is needed to understand what I’m talking about, that is not a problem.

• avcodec_find_encoder_by_name() returns NULL

  27 décembre 2019, par GiuTor

  I’m trying to compile the following example I found on ffmpeg documentation :

   /*
  
   * Copyright (c) 2001 Fabrice Bellard
  
   *
  
   * Permission is hereby granted, free of charge, to any person obtaining a copy
  
   * of this software and associated documentation files (the "Software"), to deal
  
   * in the Software without restriction, including without limitation the rights
  
   * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  
   * copies of the Software, and to permit persons to whom the Software is
  
   * furnished to do so, subject to the following conditions:
  
   *
  
   * The above copyright notice and this permission notice shall be included in
  
   * all copies or substantial portions of the Software.
  
   *
  
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  
   * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  
   * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  
   * THE SOFTWARE.
  
   */
  
  
  
   // compile with gcc -o encode_video encode_video.c -lavutil -lavcodec -lz -lm
  
  
  
  /**
  
   * @file
  
   * video encoding with libavcodec API example
  
   *
  
   * @example encode_video.c
  
   */
  
  
  
  #include 
  
  #include 
  
  #include 
  
  
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libavutil></libavutil>imgutils.h>
  
  
  
  static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt,
  
                     FILE *outfile)
  
  {
  
      int ret;
  
  
  
      /* send the frame to the encoder */
  
      if (frame)
  
          printf("Send frame %3"PRId64"\n", frame->pts);
  
  
  
      ret = avcodec_send_frame(enc_ctx, frame);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Error sending a frame for encoding\n");
  
          exit(1);
  
      }
  
  
  
      while (ret >= 0) {
  
          ret = avcodec_receive_packet(enc_ctx, pkt);
  
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
              return;
  
          else if (ret &lt; 0) {
  
              fprintf(stderr, "Error during encoding\n");
  
              exit(1);
  
          }
  
  
  
          printf("Write packet %3"PRId64" (size=%5d)\n", pkt->pts, pkt->size);
  
          fwrite(pkt->data, 1, pkt->size, outfile);
  
          av_packet_unref(pkt);
  
      }
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      const char *filename, *codec_name;
  
      const AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int i, ret, x, y;
  
      FILE *f;
  
      AVFrame *frame;
  
      AVPacket *pkt;
  
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
      if (argc &lt;= 2) {
  
          fprintf(stderr, "Usage: %s <output file="file"> <codec>\n", argv[0]);
  
          exit(0);
  
      }
  
      filename = argv[1];
  
      codec_name = argv[2];
  
  
  
      /* find the mpeg1video encoder */
  
      codec = avcodec_find_encoder_by_name(codec_name);
  
      if (!codec) {
  
          fprintf(stderr, "Codec '%s' not found\n", codec_name);
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          exit(1);
  
      }
  
  
  
      pkt = av_packet_alloc();
  
      if (!pkt)
  
          exit(1);
  
  
  
      /* put sample parameters */
  
      c->bit_rate = 400000;
  
      /* resolution must be a multiple of two */
  
      c->width = 352;
  
      c->height = 288;
  
      /* frames per second */
  
      c->time_base = (AVRational){1, 25};
  
      c->framerate = (AVRational){25, 1};
  
  
  
      /* emit one intra frame every ten frames
  
       * check frame pict_type before passing frame
  
       * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
  
       * then gop_size is ignored and the output of encoder
  
       * will always be I frame irrespective to gop_size
  
       */
  
      c->gop_size = 10;
  
      c->max_b_frames = 1;
  
      c->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      if (codec->id == AV_CODEC_ID_H264)
  
          av_opt_set(c->priv_data, "preset", "slow", 0);
  
  
  
      /* open it */
  
      ret = avcodec_open2(c, codec, NULL);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Could not open codec: %s\n", av_err2str(ret));
  
          exit(1);
  
      }
  
  
  
      f = fopen(filename, "wb");
  
      if (!f) {
  
          fprintf(stderr, "Could not open %s\n", filename);
  
          exit(1);
  
      }
  
  
  
      frame = av_frame_alloc();
  
      if (!frame) {
  
          fprintf(stderr, "Could not allocate video frame\n");
  
          exit(1);
  
      }
  
      frame->format = c->pix_fmt;
  
      frame->width  = c->width;
  
      frame->height = c->height;
  
  
  
      ret = av_frame_get_buffer(frame, 32);
  
      if (ret &lt; 0) {
  
          fprintf(stderr, "Could not allocate the video frame data\n");
  
          exit(1);
  
      }
  
  
  
      /* encode 1 second of video */
  
      for (i = 0; i &lt; 25; i++) {
  
          fflush(stdout);
  
  
  
          /* make sure the frame data is writable */
  
          ret = av_frame_make_writable(frame);
  
          if (ret &lt; 0)
  
              exit(1);
  
  
  
          /* prepare a dummy image */
  
          /* Y */
  
          for (y = 0; y &lt; c->height; y++) {
  
              for (x = 0; x &lt; c->width; x++) {
  
                  frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for (y = 0; y &lt; c->height/2; y++) {
  
              for (x = 0; x &lt; c->width/2; x++) {
  
                  frame->data[1][y * frame->linesize[1] + x] = 128 + y + i * 2;
  
                  frame->data[2][y * frame->linesize[2] + x] = 64 + x + i * 5;
  
              }
  
          }
  
  
  
          frame->pts = i;
  
  
  
          /* encode the image */
  
          encode(c, frame, pkt, f);
  
      }
  
  
  
      /* flush the encoder */
  
      encode(c, NULL, pkt, f);
  
  
  
      /* add sequence end code to have a real MPEG file */
  
      if (codec->id == AV_CODEC_ID_MPEG1VIDEO || codec->id == AV_CODEC_ID_MPEG2VIDEO)
  
          fwrite(endcode, 1, sizeof(endcode), f);
  
      fclose(f);
  
  
  
      avcodec_free_context(&amp;c);
  
      av_frame_free(&amp;frame);
  
      av_packet_free(&amp;pkt);
  
  
  
      return 0;
  
  }
  
  </codec></output>

  ffmpeg -codecs return a bunch of codecs among which libx264 and libx265. When I run the above code I get NULL from avcodec_find_encoder_by_name() :

  gt@gt-Aspire-E1-570 : /libav$ ./encode_video pippo libx264
  Codec ’libx264’ not found
  gt@gt-Aspire-E1-570 : /libav$ ./encode_video pippo x264
  Codec ’x264’ not found
  gt@gt-Aspire-E1-570 : /libav$ ./encode_video pippo H264
  Codec ’H264’ not found
  gt@gt-Aspire-E1-570 : /libav$

  Can someone help please ?

  Thanks

• Python & OpenCV - VideoCapture.read() always returns false

  21 août 2017, par Julen

  I need to extract frames from a video at a given time, and I’m using OpenCV for it. I’m using Linux Mint 18.1, but it must also run on Ubuntu.

  This code example is not working for me :

  import cv2
  
  
  
  print('making screenshot from {0}'.format('/tmp/big_buck_bunny_720p_5mb.mp4'))
  
  
  
  cap = cv2.VideoCapture(video_path)
  
  cap.set(cv2.CAP_PROP_POS_MSEC,1000)
  
  ret,frame = cap.read()
  
  print(ret)                      # This is false
  
  cv2.imwrite("image.jpg", frame) # Creates an empty file

  (I’ve checked that the path of the video is correct and that the file is not corrupted).

  I have installed the Python OpenCV 3.3.0 version :

  >>> import cv2
  
  >>> cv2.__version__
  
  '3.3.0'

  I’ve compiled and installed the source for OpenCV (with the WITH_FFMPEG=ON option) :

  git clone https://github.com/Itseez/opencv.git /tmp/opencv-3                                                                                                                                                                                
  
  /tmp/opencv-3                                                                                                                                                                                                                            
  
  mkdir -p release                                                                                                                                                                                                                            
  
  cd release                                                                                                                                                                                                                                  
  
  cmake -D WITH_FFMPEG=ON -D CMAKE_BUILD_TYPE=RELEASE -D CMAKE_INSTALL_PREFIX=/usr/local ..                                                                                                                                                   
  
  make                                                                                                                                                                                                                                        
  
  sudo make install     

  The output of ffmpeg -version is the following :

  ffmpeg version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2000-2017 the FFmpeg developers
  
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  
  libavutil      54. 31.100 / 54. 31.100
  
  libavcodec     56. 60.100 / 56. 60.100
  
  libavformat    56. 40.101 / 56. 40.101
  
  libavdevice    56.  4.100 / 56.  4.100
  
  libavfilter     5. 40.101 /  5. 40.101
  
  libavresample   2.  1.  0 /  2.  1.  0
  
  libswscale      3.  1.101 /  3.  1.101
  
  libswresample   1.  2.101 /  1.  2.101
  
  libpostproc    53.  3.100 / 53.  3.100

  What am I missing ?