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• Understanding FFMPEG Video Encoding

  20 juin 2014, par SetSlapShot

  Got this from the encoding example in ffmpeg. I can somewhat follow the authors example for audio encoding, but I find myself befuddled looking at the C code (I commented in block numbers to help me reference what I’m talking about)...

  static void video_encode_example(const char *filename)
  
  {
  
  AVCodec *codec;
  
  AVCodecContext *c= NULL;
  
  int i, out_size, size, x, y, outbuf_size;
  
  FILE *f;
  
  AVFrame *picture;
  
  uint8_t *outbuf, *picture_buf;              //BLOCK ONE
  
  printf("Video encoding\n");
  
  
  
  /* find the mpeg1 video encoder */
  
  codec = avcodec_find_encoder(CODEC_ID_MPEG1VIDEO);
  
  if (!codec) {
  
      fprintf(stderr, "codec not found\n");
  
      exit(1);                                //BLOCK TWO
  
  }
  
  
  
  c= avcodec_alloc_context();
  
  picture= avcodec_alloc_frame();
  
  /* 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->gop_size = 10; /* emit one intra frame every ten frames */
  
  c->max_b_frames=1;
  
  c->pix_fmt = PIX_FMT_YUV420P;                   //BLOCK THREE
  
  
  
  /* open it */
  
  if (avcodec_open(c, codec) < 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);
  
  }                                               //BLOCK FOUR
  
  
  
  /* alloc image and output buffer */
  
  outbuf_size = 100000;
  
  outbuf = malloc(outbuf_size);
  
  size = c->width * c->height;
  
  picture_buf = malloc((size * 3) / 2); /* size for YUV 420 */
  
  picture->data[0] = picture_buf;
  
  picture->data[1] = picture->data[0] + size;
  
  picture->data[2] = picture->data[1] + size / 4;
  
  picture->linesize[0] = c->width;
  
  picture->linesize[1] = c->width / 2;
  
  picture->linesize[2] = c->width / 2;              //BLOCK FIVE
  
  
  
  /* encode 1 second of video */
  
  for(i=0;i<25;i++) {
  
      fflush(stdout);
  
      /* prepare a dummy image */
  
      /* Y */
  
      for(y=0;yheight;y++) {
  
          for(x=0;xwidth;x++) {
  
              picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
  
          }
  
      }                                            //BLOCK SIX
  
  
  
      /* Cb and Cr */
  
      for(y=0;yheight/2;y++) {
  
          for(x=0;xwidth/2;x++) {
  
              picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
  
              picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
  
          }
  
      }                                           //BLOCK SEVEN
  
  
  
      /* encode the image */
  
      out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
  
      printf("encoding frame %3d (size=%5d)\n", i, out_size);
  
      fwrite(outbuf, 1, out_size, f);
  
  }                                              //BLOCK EIGHT
  
  
  
  /* get the delayed frames */
  
  for(; out_size; i++) {
  
      fflush(stdout);
  
      out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
  
      printf("write frame %3d (size=%5d)\n", i, out_size);
  
      fwrite(outbuf, 1, out_size, f);
  
  }                                             //BLOCK NINE
  
  
  
  /* add sequence end code to have a real mpeg file */
  
  outbuf[0] = 0x00;
  
  outbuf[1] = 0x00;
  
  outbuf[2] = 0x01;
  
  outbuf[3] = 0xb7;
  
  fwrite(outbuf, 1, 4, f);
  
  fclose(f);
  
  free(picture_buf);
  
  free(outbuf);
  
  avcodec_close(c);
  
  av_free(c);
  
  av_free(picture);
  
  }                                            //BLOCK TEN

  Here’s what I can get from the authors code block by block...

  BLOCK ONE : Initializing Variables and pointers. I couldn’t find the AVFrame struct yet in the ffmpeg source code so I don’t know what its referencing

  BLOCK TWO : Uses a codec from the file, if not found close.

  BLOCK THREE : Sets sample video parameters. Only thing I don’t really get is gop size. I read about intra frames and I still don’t get what they are.

  BLOCK FOUR : Open the file for writing...

  BLOCK FIVE : Here’s where they really start losing me. Part is probably because I don’t know exactly what AVFrame is, but why do they only use 3/2 of the image size ?

  BLOCK SIX & SEVEN : I don’t understand what they are trying to accomplish with this math.

  BLOCK EIGHT : It looks like the avcodec function does all the work here, not concerned with that for the time being..

  BLOCK NINE : Since it’s outside the 25 frame for loop I assume it gets the leftover frames ?

  BLOCK TEN : Close, free mem, etc...

  I know this is a large block of code to be confused with, any input would be helpful. I got put in over my head at work. Thanks in advance SO.

• FFMPEG error with avformat_open_input returning -135

  28 avril 2015, par LawfulEvil

  I have a DLL one of my applications uses to receive video from RTSP cameras. Under the hood, the DLL uses FFMPEG libs from this release zip :

  ffmpeg-20141022-git-6dc99fd-win64-shared.7z

  We have a wide variety of cameras in house and most of them work just fine. However, on one particular Pelco Model Number : IXE20DN-OCP, I am unable to connect. I tested the camera and rtsp connection string on VLC and it connects to the camera just fine.

  I found the connection string here : http://www.ispyconnect.com/man.aspx?n=Pelco

  rtsp://IPADDRESS:554/1/stream1

  Oddly, even if I leave the port off of VLC, it connects, so I’m guessing its the default RTSP port or that VLC tries a variety of things based on your input.

  In any case, when I attempt to connect, I get an error from av_format_open_input. It returns a code of -135. When I looked in the error code list I didn’t see that listed. For good measure, I printed out all the errors in error.h just to see what their values were.

  DumpErrorCodes - Error Code : AVERROR_BSF_NOT_FOUND = -1179861752
  
  DumpErrorCodes - Error Code : AVERROR_BUG = -558323010
  
  DumpErrorCodes - Error Code : AVERROR_BUFFER_TOO_SMALL = -1397118274
  
  DumpErrorCodes - Error Code : AVERROR_DECODER_NOT_FOUND = -1128613112
  
  DumpErrorCodes - Error Code : AVERROR_DEMUXER_NOT_FOUND = -1296385272
  
  DumpErrorCodes - Error Code : AVERROR_ENCODER_NOT_FOUND = -1129203192
  
  DumpErrorCodes - Error Code : AVERROR_EOF = -541478725
  
  DumpErrorCodes - Error Code : AVERROR_EXIT = -1414092869
  
  DumpErrorCodes - Error Code : AVERROR_EXTERNAL = -542398533
  
  DumpErrorCodes - Error Code : AVERROR_FILTER_NOT_FOUND = -1279870712
  
  DumpErrorCodes - Error Code : AVERROR_INVALIDDATA = -1094995529
  
  DumpErrorCodes - Error Code : AVERROR_MUXER_NOT_FOUND = -1481985528
  
  DumpErrorCodes - Error Code : AVERROR_OPTION_NOT_FOUND = -1414549496
  
  DumpErrorCodes - Error Code : AVERROR_PATCHWELCOME = -1163346256
  
  DumpErrorCodes - Error Code : AVERROR_PROTOCOL_NOT_FOUND = -1330794744
  
  DumpErrorCodes - Error Code : AVERROR_STREAM_NOT_FOUND = -1381258232
  
  DumpErrorCodes - Error Code : AVERROR_BUG2 = -541545794
  
  DumpErrorCodes - Error Code : AVERROR_UNKNOWN = -1313558101
  
  DumpErrorCodes - Error Code : AVERROR_EXPERIMENTAL = -733130664
  
  DumpErrorCodes - Error Code : AVERROR_INPUT_CHANGED = -1668179713
  
  DumpErrorCodes - Error Code : AVERROR_OUTPUT_CHANGED = -1668179714
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_BAD_REQUEST = -808465656
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_UNAUTHORIZED = -825242872
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_FORBIDDEN = -858797304
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_NOT_FOUND = -875574520
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_OTHER_4XX = -1482175736
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_SERVER_ERROR = -1482175992

  Nothing even close to -135. I did find this error, sort of on stack overflow, here runtime error when linking ffmpeg libraries in qt creator where the author claims it is a DLL loading problem error. I’m not sure what led him to think that, but I followed the advice and used the dependency walker (http://www.dependencywalker.com/) to checkout what dependencies it thought my DLL needed. It listed a few, but they were already provided in my install package.

  To make sure it was picking them up, I manually removed them from the install and observed a radical change in program behavior(that being my DLL didn’t load and start to run at all).

  So, I’ve got a bit of init code :

  void FfmpegInitialize()
  
  {
  
   av_lockmgr_register(&LockManagerCb);
  
   av_register_all();
  
   LOG_DEBUG0("av_register_all returned\n");
  
  }

  Then I’ve got my main open connection routine ...

  int RTSPConnect(const char *URL, int width, int height, frameReceived callbackFunction)
  
  {
  
  
  
      int errCode =0;
  
      if ((errCode = avformat_network_init()) != 0)
  
      {
  
          LOG_ERROR1("avformat_network_init returned error code %d\n", errCode);  
  
      }
  
      LOG_DEBUG0("avformat_network_init returned\n");
  
      //Allocate space and setup the the object to be used for storing all info needed for this connection
  
      fContextReadFrame = avformat_alloc_context(); // free'd in the Close method
  
  
  
      if (fContextReadFrame == 0)
  
      {
  
          LOG_ERROR1("Unable to set rtsp_transport options.   Error code = %d\n", errCode);
  
          return FFMPEG_OPTION_SET_FAILURE;
  
      }
  
  
  
      LOG_DEBUG1("avformat_alloc_context returned %p\n", fContextReadFrame);
  
  
  
      AVDictionary *opts = 0;
  
      if ((errCode = av_dict_set(&opts, "rtsp_transport", "tcp", 0)) < 0)
  
      {
  
          LOG_ERROR1("Unable to set rtsp_transport options.   Error code = %d\n", errCode);
  
          return FFMPEG_OPTION_SET_FAILURE;
  
      }
  
      LOG_DEBUG1("av_dict_set returned %d\n", errCode);
  
  
  
      //open rtsp
  
      DumpErrorCodes();
  
      if ((errCode = avformat_open_input(&fContextReadFrame, URL, NULL, &opts)) < 0)
  
      {
  
          LOG_ERROR2("Unable to open avFormat RF inputs.   URL = %s, and Error code = %d\n", URL, errCode);       
  
          LOG_ERROR2("Error Code %d = %s\n", errCode, errMsg(errCode));       
  
          // NOTE context is free'd on failure.
  
          return FFMPEG_FORMAT_OPEN_FAILURE;
  
      }
  
  ...

  To be sure I didn’t misunderstand the error code I printed the error message from ffmpeg but the error isn’t found and my canned error message is returned instead.

  My next step was going to be hooking up wireshark on my connection attempt and on the VLC connection attempt and trying to figure out what differences(if any) are causing the problem and what I can do to ffmpeg to make it work. As I said, I’ve got a dozen other cameras in house that use RTSP and they work with my DLL. Some utilize usernames/passwords/etc as well(so I know that isn’t the problem).

  Also, my run logs :

  FfmpegInitialize - av_register_all returned
  
  Open - Open called.  Pointers valid, passing control.
  
  Rtsp::RtspInterface::Open - Rtsp::RtspInterface::Open called
  
  Rtsp::RtspInterface::Open - VideoSourceString(35) = rtsp://192.168.14.60:554/1/stream1
  
  Rtsp::RtspInterface::Open - Base URL = (192.168.14.60:554/1/stream1)
  
  Rtsp::RtspInterface::Open - Attempting to open (rtsp://192.168.14.60:554/1/stream1) for WxH(320x240) video
  
  RTSPSetFormatH264 - RTSPSetFormatH264
  
  RTSPConnect - Called
  
  LockManagerCb - LockManagerCb invoked for op 1
  
  LockManagerCb - LockManagerCb invoked for op 2
  
  RTSPConnect - avformat_network_init returned
  
  RTSPConnect - avformat_alloc_context returned 019E6000
  
  RTSPConnect - av_dict_set returned 0
  
  DumpErrorCodes - Error Code : AVERROR_BSF_NOT_FOUND = -1179861752
  
  ...
  
  DumpErrorCodes - Error Code : AVERROR_HTTP_SERVER_ERROR = -1482175992
  
  RTSPConnect - Unable to open avFormat RF inputs.   URL = rtsp://192.168.14.60:554/1/stream1, and Error code = -135
  
  RTSPConnect - Error Code -135 = No Error Message Available

  I’m going to move forward with wireshark but would like to know the origin of the -135 error code from ffmpeg. When I look at the code if ’ret’ is getting set to -135, it must be happening as a result of the return code from a helper method and not directly in the avformat_open_input method.

  https://www.ffmpeg.org/doxygen/2.5/libavformat_2utils_8c_source.html#l00398

  After upgrading to the latest daily ffmpeg build, I get data on wireshark. Real Time Streaming Protocol :

  Request: SETUP rtsp://192.168.14.60/stream1/track1 RTSP/1.0\r\n
  
  Method: SETUP
  
  URL: rtsp://192.168.14.60/stream1/track1
  
  Transport: RTP/AVP/TCP;unicast;interleaved=0-1
  
  CSeq: 3\r\n
  
  User-Agent: Lavf56.31.100\r\n
  
  \r\n

  The response to that is the first ’error’ that I can detect in the initiation.

  Response: RTSP/1.0 461 Unsupported Transport\r\n
  
  Status: 461
  
  CSeq: 3\r\n
  
  Date: Sun, Jan 04 1970 16:03:05 GMT\r\n
  
  \r\n

  I’m going to guess that... it means the transport we selected was unsupported. I quick check of the code reveals I picked ’tcp’. Looking through the reply to the DESCRIBE command, it appears :

  Media Protocol: RTP/AVP

  Further, when SETUP is issued by ffmpeg, it specifies :

  Transport: RTP/AVP/TCP;unicast;interleaved=0-1

  I’m going to try, on failure here to pick another transport type and see how that works. Still don’t know where the -135 comes from.

• FFMPEG concat demuxer - how to make file formats compatible ?

  10 avril 2015, par user206481

  I need to automate mp4 concatenation server-side and I’m using FFMPEG. I will get uploads of mp4 files and I want to attach a Title.mp4 and End.mp4 to each one. I am also overlaying a soundtrack (the input videos do not have sound) There is a potential high server load so I’d like to do it as efficiently as possible using ffmpeg’s concat demuxer to avoid re-encoding the video.

  After receiving samples of each file, I am not successful and I believe it is due to mismatched file formats. My result has good Title.mp4 and audio, then when the sample uploaded mp4 is supposed to play there is garbled green/pink/red pixels on the top half of the video, then the End.mp4 plays fine. Here is my ffmpeg command and output :

  $ ffmpeg -f concat -i <(printf "file '%s'\n" Title.mp4 Sample.mp4 End.mp4) -i SoundTrack.wav -c:v copy -strict -2 -y Out.mp4
  
  
  
  ffmpeg version 2.6.1 Copyright (c) 2000-2015 the FFmpeg developers
  
  built with gcc 4.1.2 (GCC) 20080704 (Red Hat 4.1.2-55)
  
  configuration: --prefix=/home/dpmsmobi/ffmpeg_build --extra-cflags=-I/home/dpmsmobi/ffmpeg_build/include --extra-ldflags=-L/home/dpmsmobi/ffmpeg_build/lib --bindir=/home/dpmsmobi/bin --enable-gpl --enable-nonfree --enable-libmp3lame --enable-libvorbis --enable-libvpx --enable-libx264
  
    libavutil      54. 20.100 / 54. 20.100
  
    libavcodec     56. 26.100 / 56. 26.100
  
    libavformat    56. 25.101 / 56. 25.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 11.102 /  5. 11.102
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, concat, from '/dev/fd/63':
  
    Duration: N/A, start: 0.000000, bitrate: 1810 kb/s
  
      Stream #0:0: Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv), 768x512 [SAR 1:1 DAR 3:2], 1810 kb/s, 30 fps, 30 tbr, 30k tbn, 60 tbc
  
  Guessed Channel Layout for  Input Stream #1.0 : stereo
  
  Input #1, wav, from 'SoundTrack.wav':
  
    Metadata:
  
      encoded_by      : Adobe Premiere Pro CC 2014 (Maci
  
      encoder         : Adobe Premiere Pro CC 2014 (Macintosh)
  
      date            : 2015-04-07
  
      creation_time   : 11:12:10
  
      time_reference  : 0
  
    Duration: 00:00:15.06, bitrate: 1551 kb/s
  
      Stream #1:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 48000 Hz, 2 channels, s16, 1536 kb/s
  
  Output #0, mp4, to 'Out.mp4':
  
    Metadata:
  
      encoder         : Lavf56.25.101
  
      Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 768x512 [SAR 1:1 DAR 3:2], q=2-31, 1810 kb/s, 30 fps, 30 tbr, 30k tbn, 30k tbc
  
      Stream #0:1: Audio: aac ([64][0][0][0] / 0x0040), 48000 Hz, stereo, fltp, 128 kb/s
  
      Metadata:
  
        encoder         : Lavc56.26.100 aac
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (native))
  
  Press [q] to stop, [?] for help
  
  [concat @ 0x1dedc20] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
  
  [concat @ 0x1dedc20] DTS 69750 < 91000 out of order
  
  [mp4 @ 0x1f75060] Non-monotonous DTS in output stream 0:0; previous: 91000, current: 69750; changing to 91001. This may result in incorrect timestamps in the output file.
  
  
  
  <----- many more Non-monotonous DTS messages omitted here ---->
  
  
  
  frame=  427 fps=0.0 q=-1.0 Lsize=    4123kB time=00:00:15.06 bitrate=2242.5kbits/s    
  
  video:3873kB audio:236kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.344173%

  I can successfully concatenate the Title.mp4 to the End.mp4, and I can successfully concatenate two Sample.mp4 files, so I know I’ve got the ffmpeg command right. I can also successfully concat the files using the following ffmpeg command with filter_complex instead of concat demuxer (this takes considerably longer due to re-encoding) :

  ffmpeg -i Title.mp4 -i Sample.mp4 -i End.mp4 -i SoundTrack.wav -filter_complex '[0:0] [1:0] [2:0] concat=n=3:v=1 [v]' -map '[v]' -map 3:0 -crf 20 -strict -2 -y Out2.mp4 

  Here is the MediaInfo output for each type of mp4 file :

  $ mediainfo Title.mp4
  
  General
  
  Complete name                            : Title.mp4
  
  Format                                   : MPEG-4
  
  Format profile                           : Base Media / Version 2
  
  Codec ID                                 : mp42
  
  File size                                : 693 KiB
  
  Duration                                 : 3s 100ms
  
  Overall bit rate mode                    : Variable
  
  Overall bit rate                         : 1 831 Kbps
  
  Encoded date                             : UTC 2015-04-07 19:15:03
  
  Tagged date                              : UTC 2015-04-07 19:15:03
  
  ©TIM                                     : 00:00:00:00
  
  ©TSC                                     : 30
  
  ©TSZ                                     : 1
  
  
  
  Video
  
  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : Main@L3.1
  
  Format settings, CABAC                   : Yes
  
  Format settings, ReFrames                : 3 frames
  
  Codec ID                                 : avc1
  
  Codec ID/Info                            : Advanced Video Coding
  
  Duration                                 : 3s 100ms
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 1 811 Kbps
  
  Maximum bit rate                         : 3 000 Kbps
  
  Width                                    : 768 pixels
  
  Height                                   : 512 pixels
  
  Display aspect ratio                     : 3:2
  
  Frame rate mode                          : Constant
  
  Frame rate                               : 30.000 fps
  
  Standard                                 : NTSC
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.154
  
  Stream size                              : 685 KiB (99%)
  
  Language                                 : English
  
  Encoded date                             : UTC 2015-04-07 19:15:03
  
  Tagged date                              : UTC 2015-04-07 19:15:03
  
  Color range                              : Limited
  
  
  
  $ mediainfo Sample.mp4
  
  General
  
  Complete name                            : Sample.mp4
  
  Format                                   : MPEG-4
  
  Format profile                           : Base Media
  
  Codec ID                                 : isom
  
  File size                                : 2.93 MiB
  
  Duration                                 : 7s 9ms
  
  Overall bit rate                         : 3 505 Kbps
  
  Encoded date                             : UTC 1970-01-01 00:00:00
  
  Tagged date                              : UTC 1970-01-01 00:00:00
  
  Writing application                      : Lavf52.64.2
  
  
  
  Video
  
  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : Baseline@L3.1
  
  Format settings, CABAC                   : No
  
  Format settings, ReFrames                : 1 frame
  
  Format settings, GOP                     : M=1, N=30
  
  Codec ID                                 : avc1
  
  Codec ID/Info                            : Advanced Video Coding
  
  Duration                                 : 7s 9ms
  
  Bit rate                                 : 3 500 Kbps
  
  Width                                    : 768 pixels
  
  Height                                   : 512 pixels
  
  Display aspect ratio                     : 3:2
  
  Frame rate mode                          : Variable
  
  Frame rate                               : 30.250 fps
  
  Minimum frame rate                       : 23.462 fps
  
  Maximum frame rate                       : 296.053 fps
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.294
  
  Stream size                              : 2.92 MiB (100%)
  
  Language                                 : English
  
  Encoded date                             : UTC 1970-01-01 00:00:00
  
  Tagged date                              : UTC 1970-01-01 00:00:00

  I’m pretty sure it’s the mp42 vs isom Codec ID’s, and potentially the constant vs variable frame rates. I can’t change the input mp4’s but I know their format will stay the same. How can I reformat the Title and End mp4’s to match the input mp4 files so I can use ffmpeg concat demux ?