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• How to add subtitles to the encoded video using ffmpeg ?

  14 novembre 2019, par geo-freak

  I am trying to add my srt file to the video using the options which were answered here before. My input file has captions in it by default. I tried in different ways to get the captions enabled in my encoded video. Below are the commands I used.

  ffmpeg  -i input.ts -i captions.srt -b:a 32000 -ar 48000  -force_key_frames 'expr:gte(t,n_forced*3)' -acodec libfaac -hls_flags single_file -hls_list_size 0 -hls_time 3 -vcodec libx264 -s 320x240 -b:v 512000 -maxrate 512000 -c:s mov_text outfile.ts

  But I couldn’t see the captions after I see the mediainfo of the encoded file. You can see the log file of my command.

  [mpegts @ 0x56412e67b0c0] max_analyze_duration 5000000 reached at 5024000 microseconds st:1
  
  input.ts FPS 29.970030 1
  
  Input #0, mpegts, from 'input.ts':
  
    Duration: 00:03:00.07, start: 1.400000, bitrate: 2172 kb/s
  
    Program 1
  
      Metadata:
  
        service_name    : Service01
  
        service_provider: FFmpeg
  
      Stream #0:0[0x100]: Video: mpeg2video (Main), 1 reference frame ([2][0][0][0] / 0x0002), yuv420p(tv), 704x480 [SAR 10:11 DAR 4:3], Closed Captions, max. 15000 kb/s, 
  
  29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
  
      Stream #0:1[0x101](eng): Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, stereo, fltp, 192 kb/s
  
  Input #1, srt, from 'captions.srt':
  
    Duration: N/A, bitrate: N/A
  
      Stream #1:0: Subtitle: subrip
  
  [graph 0 input from stream 0:0 @ 0x56412e678540] w:704 h:480 pixfmt:yuv420p tb:1/90000 fr:30000/1001 sar:10/11 sws_param:flags=2
  
  [scaler for output stream 0:0 @ 0x56412e9caac0] w:320 h:240 flags:'bicubic' interl:0
  
  [scaler for output stream 0:0 @ 0x56412e9caac0] w:704 h:480 fmt:yuv420p sar:10/11 -> w:320 h:240 fmt:yuv420p sar:1/1 flags:0x4
  
  [graph 1 input from stream 0:1 @ 0x56412e9f74e0] tb:1/48000 samplefmt:fltp samplerate:48000 chlayout:0x3
  
  [audio format for output stream 0:1 @ 0x56412e9f7b40] auto-inserting filter 'auto-inserted resampler 0' between the filter 'Parsed_anull_0' and the filter 'audio format 
  
  for output stream 0:1'                                                                                                                                               
  
  [auto-inserted resampler 0 @ 0x56412e9f9f20] ch:2 chl:stereo fmt:fltp r:48000Hz -> ch:2 chl:stereo fmt:s16 r:48000Hz
  
  [libx264 @ 0x56412e9bb8c0] VBV maxrate specified, but no bufsize, ignored
  
  [libx264 @ 0x56412e9bb8c0] using SAR=1/1
  
  [libx264 @ 0x56412e9bb8c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
  
  [libx264 @ 0x56412e9bb8c0] profile High, level 2.0
  
  [mpegts @ 0x56412e9ba5a0] muxrate VBR, pcr every 2 pkts, sdt every 200, pat/pmt every 40 pkts
  
  Output #0, mpegts, to 'my_encoded_all-3.ts':
  
    Metadata:
  
      encoder         : Lavf57.25.100
  
      Stream #0:0: Video: h264 (libx264), -1 reference frame, yuv420p, 320x240 [SAR 1:1 DAR 4:3], q=-1--1, 512 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
  
      Metadata:
  
        encoder         : Lavc57.24.102 libx264
  
      Side data:
  
        unknown side data type 10 (24 bytes)
  
      Stream #0:1(eng): Audio: aac (libfaac), 48000 Hz, stereo, s16, 32 kb/s
  
      Metadata:
  
        encoder         : Lavc57.24.102 libfaac
  
      Stream #0:2(eng): Subtitle: subrip (srt), 320x240
  
          Metadata:
  
            encoder         : Lavc57.24.102 srt
  
      Stream mapping:
  
        Stream #0:0 -> #0:0 (mpeg2video (native) -> h264 (libx264))
  
        Stream #0:1 -> #0:1 (ac3 (native) -> aac (libfaac))
  
        Stream #1:0 -> #0:2 (subrip (srt) -> subrip (srt))
  
  Press [q] to stop, [?] for help
  
  [scaler for output stream 0:0 @ 0x56412e9caac0] w:704 h:480 fmt:yuv420p sar:40/33 -> w:320 h:240 fmt:yuv420p sar:4/3 flags:0x4
  
  No more output streams to write to, finishing.e=00:02:58.85 bitrate= 658.4kbits/s speed=13.2x
  
  frame= 5377 fps=385 q=-1.0 Lsize=   16672kB time=00:59:16.18 bitrate=  38.4kbits/s speed= 255x
  
  video:11401kB audio:1410kB subtitle:446kB other streams:0kB global headers:0kB muxing overhead: 25.753614%
  
  Input file #0 (input.ts):
  
    Input stream #0:0 (video): 5380 packets read (40279443 bytes); 5377 frames decoded; 
  
    Input stream #0:1 (audio): 5625 packets read (4320000 bytes); 5625 frames decoded (8640000 samples); 
  
    Total: 11005 packets (44599443 bytes) demuxed
  
  Input file #1 (captions.srt):
  
    Input stream #1:0 (subtitle): 10972 packets read (447147 bytes); 10972 frames decoded; 
  
    Total: 10972 packets (447147 bytes) demuxed
  
  Output file #0 (output.ts):
  
    Output stream #0:0 (video): 5377 frames encoded; 5377 packets muxed (11675098 bytes); 
  
    Output stream #0:1 (audio): 8438 frames encoded (8640000 samples); 8439 packets muxed (1444109 bytes); 
  
    Output stream #0:2 (subtitle): 10972 frames encoded; 10972 packets muxed (456619 bytes); 
  
    Total: 24788 packets (13575826 bytes) muxed
  
  [libx264 @ 0x56412e9bb8c0] frame I:81    Avg QP:15.08  size: 16370
  
  [libx264 @ 0x56412e9bb8c0] frame P:2312  Avg QP:17.77  size:  3393
  
  [libx264 @ 0x56412e9bb8c0] frame B:2984  Avg QP:22.38  size:   839
  
  [libx264 @ 0x56412e9bb8c0] consecutive B-frames: 20.6% 13.2%  9.4% 56.8%
  
  [libx264 @ 0x56412e9bb8c0] mb I  I16..4: 11.6% 37.0% 51.4%
  
  [libx264 @ 0x56412e9bb8c0] mb P  I16..4:  1.2%  3.2%  2.4%  P16..4: 33.7% 18.0% 15.7%  0.0%  0.0%    skip:25.6%
  
  [libx264 @ 0x56412e9bb8c0] mb B  I16..4:  0.2%  0.3%  0.2%  B16..8: 30.7%  9.2%  3.2%  direct: 5.1%  skip:51.1%  L0:33.6% L1:44.5% BI:21.9%
  
  [libx264 @ 0x56412e9bb8c0] final ratefactor: 16.76
  
  [libx264 @ 0x56412e9bb8c0] 8x8 transform intra:43.0% inter:49.8%
  
  [libx264 @ 0x56412e9bb8c0] coded y,uvDC,uvAC intra: 77.9% 85.1% 68.8% inter: 22.9% 21.7% 6.0%
  
  [libx264 @ 0x56412e9bb8c0] i16 v,h,dc,p: 30% 38%  5% 26%
  
  [libx264 @ 0x56412e9bb8c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 21% 23% 18%  4%  5%  7%  6%  7%  8%
  
  [libx264 @ 0x56412e9bb8c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 28% 23% 11%  5%  6%  8%  6%  7%  6%
  
  [libx264 @ 0x56412e9bb8c0] i8c dc,h,v,p: 46% 24% 21%  8%
  
  [libx264 @ 0x56412e9bb8c0] Weighted P-Frames: Y:4.2% UV:2.6%
  
  [libx264 @ 0x56412e9bb8c0] ref P L0: 73.3% 10.9% 11.1%  4.5%  0.1%
  
  [libx264 @ 0x56412e9bb8c0] ref B L0: 92.1%  6.3%  1.6%
  
  [libx264 @ 0x56412e9bb8c0] ref B L1: 97.4%  2.6%

  I found no issues in encoding but I couldn’t see the captions enabled in my output encoded video. I played it in my VLC player. No tracks for subtitles.

  Can’t we add the subtitles to a video while encoding ?

  Any help in achieving this would be appreciated.

• 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

• Encode buffer captured by OpenGL in C

  4 janvier 2020, par M. Ying

  I am trying to use OpenGL to capture the back buffer of my computer’s screen, and then H.264 encode the buffer using FFMPEG’s libavcodec library. The issue I’m having is that I would like to encode the video in AV_PIX_FMT_420P, but the back buffer capture function provided by OpenGL, glReadPixels(), only supports formats like GL_RGB. As you can see below, I try to use FFMPEG’s swscale() function to convert from RGB to YUV, but the following code crashes at the swscale() line. Any ideas on how I can encode the OpenGL backbuffer ?

  // CAPTURE BACK BUFFER USING OPENGL
  
      int width = 1280, height = 720;
  
      BYTE* pixels = (BYTE *) malloc(sizeof(BYTE));
  
      glReadPixels(0, 720, width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels);
  
  
  
  //CREATE FFMPEG VARIABLES
  
      avcodec_register_all();
  
  
  
      AVCodec *codec;
  
      AVCodecContext *context;
  
      struct SwsContext *sws;
  
      AVPacket packet;
  
      AVFrame *frame;
  
  
  
      codec = avcodec_find_encoder(AV_CODEC_ID_H264);
  
      context = avcodec_alloc_context3(encoder->codec);
  
      context->dct_algo = FF_DCT_FASTINT;
  
      context->bit_rate = 400000;
  
      context->width = width;
  
      context->height = height;
  
      context->time_base.num = 1;
  
      context->time_base.den = 30;
  
      context->gop_size = 1;
  
      context->max_b_frames = 1;
  
      context->pix_fmt = AV_PIX_FMT_YUV420P;
  
  
  
      avcodec_open2(context, codec, NULL);
  
  
  
  // CONVERT TO YUV AND ENCODE
  
      int frame_size = avpicture_get_size(AV_PIX_FMT_YUV420P, out_width, out_height);
  
      encoder->frame_buffer = malloc(frame_size);
  
      avpicture_fill((AVPicture *) encoder->frame, (uint8_t *) encoder->frame_buffer, AV_PIX_FMT_YUV420P, out_width, out_height);
  
      sws = sws_getContext(in_width, in_height, AV_PIX_FMT_RGB32, out_width, out_height, AV_PIX_FMT_YUV420P, SWS_FAST_BILINEAR, 0, 0, 0);
  
  
  
      uint8_t *in_data[1] = {(uint8_t *) pixels};
  
      int in_linesize[1] = {width * 4};
  
  
  
  
  
  // PROGRAM CRASHES HERE
  
  
  
  
  
      sws_scale(encoder->sws, in_data, in_linesize, 0, encoder->in_height, encoder->frame->data, encoder->frame->linesize);
  
  
  
      av_free_packet(&packet);
  
      av_init_packet(&packet);
  
      int success;
  
  
  
      avcodec_encode_video2(context, &packet, frame, &success);