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• FFMPEG : sws_scale returns error : Slice parameters 0, 2160 are invalid

  21 janvier 2020, par Matthew Czarnek

  I’m trying to follow a tutorial to display ffmpeg AVFrame output in SDL. The tutorial(and all examples I’m seeing online) are still using ’sws_getContext’, which has been deprecated and removed from the newest version of ffmpeg. Trying to change current pixel format from whatever it currently is to PIX_FMT_YUV420P, so I can display it. I believe I need the sws_scale function to accomplish this.

  However, sws_scale is the function that causes a command line error of :
  Slice parameters 0, 2160 are invalid

  Here is all my code associate with swsContext :

  struct SwsContext* av_sws_ctx = NULL;
  
  av_sws_ctx = sws_alloc_context();
  
  
  
  sws_init_context(av_sws_ctx, NULL, NULL);
  
  
  
  sws_scale(av_sws_ctx, (uint8_t const* const*)av_frame->data,
  
                          av_frame->linesize, 0, av_codec_context->height,
  
                          av_frame->data, av_frame->linesize);

  Further complicating the matter, SwsContext is only defined internal to ffmpeg, externally I can’t set/get any variables or even view them in the debugger.

  int sws_scale(struct SwsContext *c, const uint8_t *const srcSlice[], const int srcStride[], int srcSliceY, int srcSliceH, uint8_t *const dst[], const int dstStride[] )

  The vales of other parameters, other than av_sws_ctx :

  srcSlice: av_frame->data = 
  
       8 arrays, first is filled with "\x10\x10\x10\x10\x10..."
  
       second and third are "€€€€€€€€€€€€€€€€€..."
  
       rest are NULL
  
  linesize(av_frame->linesize) is an array:
  
      3840,1920,1920,0,0,0,0,0
  
  srcSliceY:0
  
  srcSliceH:2160
  
  dest: same as second parameter (av_frame->data)
  
  dstStride: av_frame->linesize again

  If I drill into sws_scale source code, I find that this error is thrown by this chunk of code :

  if ((srcSliceY & (macro_height-1)) ||
  
          ((srcSliceH& (macro_height-1)) && srcSliceY + srcSliceH != c->srcH) ||
  
          srcSliceY + srcSliceH > c->srcH) {
  
          av_log(c, AV_LOG_ERROR, "Slice parameters %d, %d are invalid\n", srcSliceY, srcSliceH);
  
          return AVERROR(EINVAL);
  
      }

  I assume that the issue therefore is that the height of my video is bigger than sws_context(4k video). But can’t figure out how to tell sws_context what it’s height should be using sws_alloc_context or sws_init_context or any other function.

  See something I’m missing ? Thank you.

• Error -138 returns "Error number -138 occurred"

  29 avril 2016, par bot1131357

  I am trying to create a program that listens for a period of time, and then times out so that it can return to work on other tasks and retry again later. Here is the code I am testing with :

  AVFormatContext *pFormatCtx = NULL;
  
  AVCodecContext *codecCtx = NULL;
  
  AVCodec *codec;
  
  int ret = 0;
  
  
  
  // Register all formats and codecs
  
  av_register_all();
  
  avformat_network_init(); // for network streaming
  
  
  
  AVDictionary *d = NULL;           // "create" an empty dictionary
  
  av_dict_set(&d, "timeout", "5", 0); // add an entry
  
  av_dict_set(&d, "rtsp_flags", "listen", 0); // add an entry
  
  
  
  char filename[100];
  
  sprintf_s(filename, sizeof(filename), "%s", "rtsp://127.0.0.1:8554/demo");
  
  
  
  
  
  //:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
  
  printf_s("Open video file.\n");
  
  // Open video file
  
  ret = avformat_open_input(&pFormatCtx, filename, NULL, &d);   // Returns -138 here 
  
  if (ret <0)
  
  {
  
      printf_s("Failed: cannot open input.\n");
  
      av_strerror(ret, errbuf, ERRBUFFLEN);
  
      fprintf(stderr, "avformat_open_input() fail: %s\n", errbuf);
  
      continue;
  
      //return -1; // Couldn't find stream information
  
  }

  In the listening mode, avformat_open_input() returns -138. Using av_strerror() gives the following explanation : "Error number -138 occurred"

  Is this an Easter egg ? What does -138 stand for ?

• Problem in setting video thumbnail with ffmpeg

  8 avril 2022, par Simran Marok

  I'm trying to add thumbnail to a mkv video with the following command : ffmpeg -y -i video.mkv -i image.jpg -map 1 -map 0 -c copy -disposition:0 attached_pic out.mkv. However this command replaces all frames in the video with that image and no sound. Am I doing something wrong. I'm using latest version of ffmpeg.