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• FFMPEG avformat_write_header changing my stream time_base

  24 avril 2015, par cesarpachon

  I am muxing video using ffmpeg 2.1.3 with libavcodec 55.39.101 (forced to that version because is the one available in google-chrome PNACL port project). all my frames seems to have bad the time. they try to be rendered all at once at the beggining of the video when playing it.

  I am setting the stream time base to 1/25, but just after calling avformat_write_header, it has the value of -18082736/1.
  in each frame, when I print the stream time_base it says 1/12800, while the time_base of codec is always ok (1/25).

  console log before and after av_format_write_header :

  before avformat_write_header stream time_base: 1/25
  
  after avformat_write_header ret 0 stream time_base: -18082736/1

  the code (abreviated to keep the post short, all calls in the original version had error checking) :

  AVCodecContext *codecContext;
  
  AVCodec * codec = avcodec_find_encoder(codec_id);  
  
  myOutputStream->stream = avformat_new_stream(outputFormatContext, *codec);
  
  myOutputStream->stream->id = outputFormatContext->nb_streams-1;
  
  codecContext = myOutputStream->stream->codec;
  
  codecContext->codec_id = codec_id;
  
  codecContext->bit_rate = 400000;
  
  codecContext->width    = width;
  
  codecContext->height   = height;
  
  myOutputStream->stream->time_base = (AVRational){ 1, 25 };
  
  codecContext->time_base       = myOutputStream->stream->time_base;
  
  codecContext->gop_size      = 12; 
  
  codecContext->pix_fmt       = AV_PIX_FMT_YUV420P;
  
  AVDictionary *opt = NULL;
  
  av_dict_copy(&opt, opt_arg, 0);
  
  ret = avcodec_open2(codecContext, codec, &opt);
  
  av_dict_free(&opt);
  
  myOutputStream->frame = alloc_picture(codecContext->pix_fmt, codecContext->width, codecContext->height);
  
    myOutputStream->tmp_frame = alloc_picture(AV_PIX_FMT_YUV420P, codecContext->width, codecContext->height);
  
  
  
  //before: printing g_outputContext->stream time_base here
  
  ret = avformat_write_header(g_outputContext, &opt);
  
  //after: printing g_outputContext->stream time_base here

  If I run ffmpeg -i on the final video, I got this (why duration is zero ?) :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test4.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2mp41
  
      encoder         : Lavf55.19.104
  
    Duration: 00:00:00.05, start: 0.000000, bitrate: 99549 kb/s
  
      Stream #0:0(und): Video: mpeg4 (Simple Profile) (mp4v / 0x7634706D), yuv420p, 800x600 [SAR 1:1 DAR 4:3], 463106 kb/s, 12800 fps, 12800 tbr, 12800 tbn, 25 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler

• Decoding then re-encoding frames in reverse order with ffmpeg

  21 août 2014, par user3875919

  I am pretty new to ffmpeg, and now I want to decode the frames and encode it back in reverse order. I have used this tutorial for decoding the video and this example to encode it back. I can decode the frames properly, but when I re-encode it, I get a dummy image rather than clear video. How can I get the actual reversed video ?

  static void video_encode_example(const char *filename, int codec_id)
  
  {
  
      AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
      int i, ret, x, y, got_output;
  
      FILE *f;
  
      struct SwsContext *sws_ctx = NULL;
  
      AVFrame *frame;
  
      AVFrame *frameRGB = NULL;
  
      AVPacket pkt;
  
      uint8_t endcode[] = { 0, 0, 1, 0xb7 };
  
  
  
      printf("Encode video file %s\n", filename);
  
  
  
      /* find the mpeg1 video encoder */
  
      codec = avcodec_find_encoder(codec_id);
  
      if (!codec) {
  
          fprintf(stderr, "Codec not found\n");
  
          exit(1);
  
      }
  
  
  
      c = avcodec_alloc_context3(codec);
  
      if (!c) {
  
          fprintf(stderr, "Could not allocate video codec context\n");
  
          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};
  
      /* 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 */
  
      if (avcodec_open2(c, codec, NULL) < 0) {
  
          fprintf(stderr, "Could not open codec\n");
  
          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;
  
  
  
      /* the image can be allocated by any means and av_image_alloc() is
  
       * just the most convenient way if av_malloc() is to be used */
  
      ret = av_image_alloc(frame->data, frame->linesize, c->width, c->height,
  
                           c->pix_fmt, 32);
  
      if (ret < 0) {
  
          fprintf(stderr, "Could not allocate raw picture buffer\n");
  
          exit(1);
  
      }
  
  
  
      /* encode 1 second of video */
  
      for (i = 0; i < 25; i++) {
  
          av_init_packet(&pkt);
  
          pkt.data = NULL;    // packet data will be allocated by the encoder
  
          pkt.size = 0;
  
  
  
          fflush(stdout);
  
          /* prepare a dummy image */
  
          /* Y */
  
          for (y = 0; y < c->height; y++) {
  
              for (x = 0; x < c->width; x++) {
  
                  frame->data[0][y * frame->linesize[0] + x] = x + y + i * 3;
  
              }
  
          }
  
  
  
          /* Cb and Cr */
  
          for (y = 0; y < c->height/2; y++) {
  
              for (x = 0; x < 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 */
  
          ret = avcodec_encode_video2(c, &pkt, frame, &got_output);
  
          if (ret < 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              // Convert the image from its native format to RGB
  
              sws_scale
  
              (
  
                  sws_ctx,
  
                  (uint8_t const * const *)frame->data,
  
                  frame->linesize,
  
                  0,
  
                  c->height,
  
                  frameRGB->data,
  
                  frameRGB->linesize
  
              );
  
              printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&pkt);
  
          }
  
      }
  
  
  
      /* get the delayed frames */
  
      for (got_output = 1; got_output; i++) {
  
          fflush(stdout);
  
  
  
          ret = avcodec_encode_video2(c, &pkt, NULL, &got_output);
  
          if (ret < 0) {
  
              fprintf(stderr, "Error encoding frame\n");
  
              exit(1);
  
          }
  
  
  
          if (got_output) {
  
              printf("Write frame %3d (size=%5d)\n", i, pkt.size);
  
              fwrite(pkt.data, 1, pkt.size, f);
  
              av_free_packet(&pkt);
  
          }
  
      }
  
  
  
      /* add sequence end code to have a real mpeg file */
  
      fwrite(endcode, 1, sizeof(endcode), f);
  
      fclose(f);
  
  
  
      avcodec_close(c);
  
      av_free(c);
  
      av_freep(&frame->data[0]);
  
      av_frame_free(&frame);
  
      printf("\n");
  
  }

• capture my webcam and encode to mp4 with ffmpeg, but the x264 works bad

  17 septembre 2015, par zhangxm1991

  here is my version :
  ffmpeg version : 2.3.3
  libx264 version:142.x

  I wat to capture my video and use ffmpeg and x264 to a mp4 file. the solution is 320x240.
  But i found that the video file is so big. Then i found that the P frame and B frame is very big, even nearly equal to the I frame.I do not know why.

  here is my code :

      c->codec_id = codec_id;
  
      c->bit_rate = 400000;
  
      c->width    = 320;
  
      c->height   = 240;
  
      c->time_base.den = 10;
  
      c->time_base.num = 1;
  
      c->pix_fmt       = AV_PIX_FMT_YUV420P;

  Here is my program output :

  [libx264 @ 0xb6200fc0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX 
  
  
  
  [libx264 @ 0xb6200fc0] profile High, level 1.3
  
  
  
  [libx264 @ 0xb6200fc0] 264 - core 142 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=10 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=400 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  
  
  Output #0, mp4, to '/home/2014_09_12/0002b6429579/5/2014_09_12_18_39_12_600.mp4':
  
  
  
      Stream #0:0: Video: h264 (libx264), yuv420p, 320x240, q=-1--1, 400 kb/s, 10 tbc
  
  
  
      Stream #0:1: Audio: aac, 8000 Hz, mono, fltp, 32 kb/s
  
  
  
  [mp4 @ 0xb62005e0] Using AVStream.codec.time_base as a timebase hint to the muxer is deprecated. Set AVStream.time_base instead.
  
  
  
  [mp4 @ 0xb62005e0] Using AVStream.codec.time_base as a timebase hint to the muxer is deprecated. Set AVStream.time_base instead.
  
  
  
  [mp4 @ 0xb62005e0] Encoder did not produce proper pts, making some up.
  
  
  
  [libx264 @ 0xb6200fc0] frame I:3     Avg QP: 2.79  size: 72996
  
  
  
  [libx264 @ 0xb6200fc0] frame P:383   Avg QP: 0.14  size: 54075
  
  
  
  [libx264 @ 0xb6200fc0] frame B:216   Avg QP: 1.95  size: 64784
  
  
  
  [libx264 @ 0xb6200fc0] consecutive B-frames: 30.1% 63.2%  6.0%  0.7%
  
  
  
  [libx264 @ 0xb6200fc0] mb I  I16..4: 16.1% 12.7% 71.2%
  
  
  
  [libx264 @ 0xb6200fc0] mb P  I16..4:  3.5%  5.1% 15.9%  P16..4: 20.3% 22.8% 14.0%  0.0%  0.0%    skip:18.3%
  
  
  
  [libx264 @ 0xb6200fc0] mb B  I16..4:  0.4%  2.5%  8.2%  B16..8: 32.6% 19.8% 13.5%  
  
  direct:22.2%  skip: 0.8%  L0:25.5% L1:12.8% BI:61.6%
  
  
  
  [libx264 @ 0xb6200fc0] final ratefactor: -32.89
  
  
  
  [libx264 @ 0xb6200fc0] 8x8 transform intra:21.0% inter:29.6%
  
  
  
  [libx264 @ 0xb6200fc0] coded y,uvDC,uvAC intra: 100.0% 100.0% 100.0% inter: 83.3% 80.9% 80.9%
  
  
  
  [libx264 @ 0xb6200fc0] i16 v,h,dc,p:  5%  7% 42% 46%
  
  
  
  [libx264 @ 0xb6200fc0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 14% 12% 23%  8%  6%  6%  8%  9% 14%
  
  
  
  [libx264 @ 0xb6200fc0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 12% 11% 19% 10%  8%  8% 10% 10% 12%
  
  
  
  [libx264 @ 0xb6200fc0] i8c dc,h,v,p: 78%  3%  4% 15%
  
  
  
  [libx264 @ 0xb6200fc0] Weighted P-Frames: Y:0.5% UV:0.3%
  
  
  
  [libx264 @ 0xb6200fc0] ref P L0: 43.4% 14.6% 19.0% 22.9%  0.1%
  
  
  
  [libx264 @ 0xb6200fc0] ref B L0: 63.3% 35.7%  1.1%
  
  
  
  [libx264 @ 0xb6200fc0] ref B L1: 97.0%  3.0%
  
  
  
  [libx264 @ 0xb6200fc0] kb/s:4.53
  
  
  
  [aac @ 0xb6201ba0] 2 frames left in the queue on closing