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• 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

• FFMPEG Audio/video out of sync after cutting and concatonating

  31 janvier 2020, par Ham789

  I am attempting to take cuts from a set of videos and concatonate them together with the concat demuxer.

  However, each video’s audio is out of sync in the output. At the beggening of each clip there is a short period of silence before the audio begins.

  For each video, I decode it, trim a clip from it and then encode it to 4k resolution at 25 fps with its audio :

  ffmpeg -ss 0.5 -t 0.5 -i input_video1.mp4 -r 25 -vf scale=3840:2160 output_video1.mp4

  I then take each of these videos and concatonate them together with the concat demuxer :

  ffmpeg -f concat -safe 0 -i cut_videos.txt -c copy -y output.mp4

  I am taking short cuts of each video (approximately 0.5s)

  I am using Python’s subprocess to automate the cutting and concatonating of the videos.

  It seems the audio becomes out of sync after the trimming step (not the concatonation) as when I play back the intermediate cut video files (output_video1.mp4 in the above code), there seems to be the same silence before the audio comes in at the start of the video.

  When I concatonate the videos, I get a lot of these warnings :

  [mp4 @ 0000021a252ce080] Non-monotonous DTS in output stream 0:1; previous: 51792, current: 50009; changing to 51793. This may result in incorrect timestamps in the output file.

  From this post, it seems to be a problem with cutting the videos and their timestamps. The solution proposed in the post is to decode, cut and then encode the video however I am already doing that.

  How can I ensure the audio and video are in sync ?

• ffmpeg - Frames flip upside-down when using -c:v copy

  26 décembre 2019, par Berndi

  I tried to just copy (a period of time of) an AVI-Video into another newly created AVI-file using ffmpeg’s copy option.
  (On Windows 32-bit)

  ffmpeg -i "C:\Temp\zzz\myAvi.avi" -c copy -t 00:00:10 "C:\Temp\zzz\myAviNew.avi"

  Why are the pictures flipped upside-down in the resulting file ?
  (Also the generated new audio is a little distorted.)

  Using the same command again on the newly created file will not flip them back again - the pictures stay upside down.
  Why this ? Is it a bug ?

  Console brings the following output :

   ffmpeg version N-50911-g9efcfbe Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Mar 13 2013 21:26:48 with gcc 4.7.2 (GCC)
  
    configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-av
  
  isynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enab
  
  le-libass --enable-libbluray --enable-libcaca --enable-libfreetype --enable-libg
  
  sm --enable-libilbc --enable-libmp3lame --enable-libopencore-amrnb --enable-libo
  
  pencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-li
  
  bschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-lib
  
  twolame --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enabl
  
  e-libvpx --enable-libx264 --enable-libxavs --enable-libxvid --enable-zlib
  
    libavutil      52. 19.100 / 52. 19.100
  
    libavcodec     55.  0.100 / 55.  0.100
  
    libavformat    55.  0.100 / 55.  0.100
  
    libavdevice    54.  4.100 / 54.  4.100
  
    libavfilter     3. 45.103 /  3. 45.103
  
    libswscale      2.  2.100 /  2.  2.100
  
    libswresample   0. 17.102 /  0. 17.102
  
    libpostproc    52.  2.100 / 52.  2.100
  
  [avi @ 02537ba0] non-interleaved AVI
  
  Guessed Channel Layout for  Input Stream #0.1 : stereo
  
  Input #0, avi, from 'C:\Temp\zzz\Hase.avi':
  
    Duration: 00:00:35.92, start: 0.000000, bitrate: 171375 kb/s
  
      Stream #0:0: Video: rawvideo, bgra, 768x576, 12 tbr, 12 tbn, 12 tbc
  
      Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16
  
  , 1411 kb/s
  
  Output #0, avi, to 'C:\Temp\zzz\HaseNew.avi':
  
    Metadata:
  
      ISFT            : Lavf55.0.100
  
      Stream #0:0: Video: rawvideo, bgra, 768x576, q=2-31, 12 tbn, 12 tbc
  
      Stream #0:1: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, 141
  
  1 kb/s
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  frame=   11 fps=0.0 q=-1.0 size=   19162kB time=00:00:00.91 bitrate=171242.4kbit
  
  frame=   16 fps= 12 q=-1.0 size=   27874kB time=00:00:01.33 bitrate=171255.5kbit
  
  ...
  
  ...
  
  ...
  
  frame=  120 fps=5.4 q=-1.0 size=  209083kB time=00:00:09.99 bitrate=171280.6kbit
  
  frame=  121 fps=5.5 q=-1.0 Lsize=  210834kB time=00:00:10.08 bitrate=171288.2kbi
  
  ts/s
  
  video:209088kB audio:1723kB subtitle:0 global headers:0kB muxing overhead 0.0112
  
  76%
  
  
  
  C:\WINDOWS\system32>