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• Parsing The Clue Chronicles

  30 décembre 2018, par Multimedia Mike — Game Hacking

  A long time ago, I procured a 1999 game called Clue Chronicles : Fatal Illusion, based on the classic board game Clue, a.k.a. Cluedo. At the time, I was big into collecting old, unloved PC games so that I could research obscure multimedia formats.

  
  
  

  Surveying the 3 CD-ROMs contained in the box packaging revealed only Smacker (SMK) videos for full motion video which was nothing new to me or the multimedia hacking community at the time. Studying the mix of data formats present on the discs, I found a selection of straightforward formats such as WAV for audio and BMP for still images. I generally find myself more fascinated by how computer games are constructed rather than by playing them, and this mix of files has always triggered a strong “I could implement a new engine for this !” feeling in me, perhaps as part of the ScummVM project which already provides the core infrastructure for reimplementing engines for 2D adventure games.

  Tying all of the assets together is a custom high-level programming language. I have touched on this before in a blog post over a decade ago. The scripts are in a series of files bearing the extension .ini (usually reserved for configuration scripts, but we’ll let that slide). A representative sample of such a script can be found here :

  clue-chronicles-scarlet-1.txt

  What Is This Language ?
  At the time I first analyzed this language, I was still primarily a C/C++-minded programmer, with a decent amount of Perl experience as a high level language, and had just started to explore Python. I assessed this language to be “mildly object oriented with C++-type comments (‘//’) and reliant upon a number of implicit library functions”. Other people saw other properties. When I look at it nowadays, it reminds me a bit more of JavaScript than C++. I think it’s sort of a Rorschach test for programming languages.

  Strangely, I sort of had this fear that I would put a lot of effort into figuring out how to parse out the language only for someone to come along and point out that it’s a well-known yet academic language that already has a great deal of supporting code and libraries available as open source. Google for “spanish dolphins far side comic” for an illustration of the feeling this would leave me with.

  It doesn’t matter in the end. Even if such libraries exist, how easy would they be to integrate into something like ScummVM ? Time to focus on a workable approach to understanding and processing the format.

  Problem Scope
  So I set about to see if I can write a program to parse the language seen in these INI files. Some questions :

  1. How large is the corpus of data that I need to be sure to support ?
  2. What parsing approach should I take ?
  3. What is the exact language format ?
  4. Other hidden challenges ?

  To figure out how large the data corpus is, I counted all of the INI files on all of the discs. There are 138 unique INI files between the 3 discs. However, there are 146 unique INI files after installation. This leads to a hidden challenge described a bit later.

  What parsing approach should I take ? I worried a bit too much that I might not be doing this the “right” way. I’m trying to ignore doubts like this, like how “SQL Shame” blocked me on a task for a little while a few years ago as I concerned myself that I might not be using the purest, most elegant approach to the problem. I know I covered language parsing a lot time ago in university computer science education and there is a lot of academic literature to the matter. But sometimes, you just have to charge in and experiment and prototype and see what falls out. In doing so, I expect to have a better understanding of the problems that need to solved and the right questions to ask, not unlike that time that I wrote a continuous integration system from scratch because I didn’t actually know that “continuous integration” was the keyword I needed.

  Next, what is the exact language format ? I realized that parsing the language isn’t the first and foremost problem here– I need to know exactly what the language is. I need to know what the grammar are keywords are. In essence, I need to reverse engineer the language before I write a proper parser for it. I guess that fits in nicely with the historical aim of this blog (reverse engineering).

  Now, about the hidden challenges– I mentioned that there are 8 more INI files after the game installs itself. Okay, so what’s the big deal ? For some reason, all of the INI files are in plaintext on the CD-ROM but get compressed (apparently, according to file size ratios) when installed to the hard drive. This includes those 8 extra INI files. I thought to look inside the CAB installation archive file on the CD-ROM and the files were there… but all in compressed form. I suspect that one of the files forms the “root” of the program and is the launching point for the game.

  Parsing Approach
  I took a stab at parsing an INI file. My approach was to first perform lexical analysis on the file and create a list of 4 types : symbols, numbers, strings, and language elements ([]{}()=., :). Apparently, this is the kind of thing that Lex/Flex are good at. This prototyping tool is written in Python, but when I port this to ScummVM, it might be useful to call upon the services of Lex/Flex, or another lexical analyzer, for there are many. I have a feeling it will be easier to use better tools when I understand the full structure of the language based on the data available.
  
  The purpose of this tool is to explore all the possibilities of the existing corpus of INI files. To that end, I ran all 138 of the plaintext files through it, collected all of the symbols, and massaged the results, assuming that the symbols that occurred most frequently are probably core language features. These are all the symbols which occur more than 1000 times among all the scripts :

     6248 false
     5734 looping
     4390 scripts
     3877 layer
     3423 sequentialscript
     3408 setactive
     3360 file
     3257 thescreen
     3239 true
     3008 autoplay
     2914 offset
     2599 transparent
     2441 text
     2361 caption
     2276 add
     2205 ge
     2197 smackanimation
     2196 graphicscript
     2196 graphic
     1977 setstate
     1642 state
     1611 skippable
     1576 desc
     1413 delayscript
     1298 script
     1267 seconds
     1019 rect
  

  About That Compression
  I have sorted out at least these few details of the compression :

  bytes 0-3    "COMP" (a pretty strong sign that this is, in fact, compressed data)
  bytes 4-11   unknown
  bytes 12-15  size of uncompressed data
  bytes 16-19  size of compressed data (filesize - 20)
  bytes 20-    compressed payload
  

  The compression ratios are on the same order of gzip. I was hoping that it was stock zlib data. However, I have been unable to prove this. I wrote a Python script that scrubbed through the first 100 bytes of payload data and tried to get Python’s zlib.decompress to initialize– no luck. It’s frustrating to know that I’ll have to reverse engineer a compression algorithm that deals with just 8 total text files if I want to see this effort through to fruition.

  Update, January 15, 2019
  Some folks expressed interest in trying to sort out the details of the compression format. So I have posted a followup in which I post some samples and go into deeper details about things I have tried :

  Reverse Engineering Clue Chronicles Compression

  The post Parsing The Clue Chronicles first appeared on Breaking Eggs And Making Omelettes.

• ffmpeg : Trying to access Ebur128Context->integrated_loudness but unsuccessful

  12 avril 2019, par Sourabh Jain

  [FFMPEG] Trying to access Ebur128Context->integrated_loudness but unsuccessful

  I am trying to run ebur128Filter on audio file . similar to be doing
  [http://ffmpeg.org/doxygen/2.6/f__ebur128_8c_source.html#l00135]

  ffmpeg -i sample.wav -filter_complex ebur128=peak=true -f null -

  result of which is :

  [Parsed_ebur128_0 @ 0x7f9d38403ec0] Summary:
  
  
  
  Integrated loudness:
  
  I: -15.5 LUFS
  
  Threshold: -25.6 LUFS
  
  
  
  Loudness range:
  
  LRA: 1.5 LU
  
  Threshold: -35.5 LUFS
  
  LRA low: -16.3 LUFS
  
  LRA high: -14.8 LUFS
  
  
  
  True peak:
  
  Peak: -0.4 dBFS 

  /*
  
   * Copyright (c) 2010 Nicolas George
  
   * Copyright (c) 2011 Stefano Sabatini
  
   * Copyright (c) 2012 Clément Bœsch
  
   *
  
   * 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.
  
   */
  
  
  
  /**
  
   * @file
  
   * API example for audio decoding and filtering
  
   * @example filtering_audio.c
  
   */
  
  
  
  #include 
  
  
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavfilter></libavfilter>buffersink.h>
  
  #include <libavfilter></libavfilter>buffersrc.h>
  
  #include <libavutil></libavutil>opt.h>
  
  
  
  #define MAX_CHANNELS 63
  
  
  
  
  
  
  
  static const char *filter_descr = "ebur128=peak=true";
  
  
  
  static AVFormatContext *fmt_ctx;
  
  static AVCodecContext *dec_ctx;
  
  AVFilterContext *buffersink_ctx;
  
  AVFilterContext *buffersrc_ctx;
  
  AVFilterGraph *filter_graph;
  
  static int audio_stream_index = -1;
  
  
  
  struct rect { int x, y, w, h; };
  
  
  
  
  
  struct hist_entry {
  
      int count;                      ///&lt; how many times the corresponding value occurred
  
      double energy;                  ///&lt; E = 10^((L + 0.691) / 10)
  
      double loudness;                ///&lt; L = -0.691 + 10 * log10(E)
  
  };
  
  
  
  
  
  struct integrator {
  
      double *cache[MAX_CHANNELS];    ///&lt; window of filtered samples (N ms)
  
      int cache_pos;                  ///&lt; focus on the last added bin in the cache array
  
      double sum[MAX_CHANNELS];       ///&lt; sum of the last N ms filtered samples (cache content)
  
      int filled;                     ///&lt; 1 if the cache is completely filled, 0 otherwise
  
      double rel_threshold;           ///&lt; relative threshold
  
      double sum_kept_powers;         ///&lt; sum of the powers (weighted sums) above absolute threshold
  
      int nb_kept_powers;             ///&lt; number of sum above absolute threshold
  
      struct hist_entry *histogram;   ///&lt; histogram of the powers, used to compute LRA and I
  
  };
  
  
  
  typedef struct EBUR128Context {
  
      const AVClass *class;           ///&lt; AVClass context for log and options purpose
  
  
  
      /* peak metering */
  
      int peak_mode;                  ///&lt; enabled peak modes
  
      double *true_peaks;             ///&lt; true peaks per channel
  
      double *sample_peaks;           ///&lt; sample peaks per channel
  
      double *true_peaks_per_frame;   ///&lt; true peaks in a frame per channel
  
  #if CONFIG_SWRESAMPLE
  
      SwrContext *swr_ctx;            ///&lt; over-sampling context for true peak metering
  
      double *swr_buf;                ///&lt; resampled audio data for true peak metering
  
      int swr_linesize;
  
  #endif
  
  
  
      /* video  */
  
      int do_video;                   ///&lt; 1 if video output enabled, 0 otherwise
  
      int w, h;                       ///&lt; size of the video output
  
      struct rect text;               ///&lt; rectangle for the LU legend on the left
  
      struct rect graph;              ///&lt; rectangle for the main graph in the center
  
      struct rect gauge;              ///&lt; rectangle for the gauge on the right
  
      AVFrame *outpicref;             ///&lt; output picture reference, updated regularly
  
      int meter;                      ///&lt; select a EBU mode between +9 and +18
  
      int scale_range;                ///&lt; the range of LU values according to the meter
  
      int y_zero_lu;                  ///&lt; the y value (pixel position) for 0 LU
  
      int y_opt_max;                  ///&lt; the y value (pixel position) for 1 LU
  
      int y_opt_min;                  ///&lt; the y value (pixel position) for -1 LU
  
      int *y_line_ref;                ///&lt; y reference values for drawing the LU lines in the graph and the gauge
  
  
  
      /* audio */
  
      int nb_channels;                ///&lt; number of channels in the input
  
      double *ch_weighting;           ///&lt; channel weighting mapping
  
      int sample_count;               ///&lt; sample count used for refresh frequency, reset at refresh
  
  
  
      /* Filter caches.
  
       * The mult by 3 in the following is for X[i], X[i-1] and X[i-2] */
  
      double x[MAX_CHANNELS * 3];     ///&lt; 3 input samples cache for each channel
  
      double y[MAX_CHANNELS * 3];     ///&lt; 3 pre-filter samples cache for each channel
  
      double z[MAX_CHANNELS * 3];     ///&lt; 3 RLB-filter samples cache for each channel
  
  
  
  #define I400_BINS  (48000 * 4 / 10)
  
  #define I3000_BINS (48000 * 3)
  
      struct integrator i400;         ///&lt; 400ms integrator, used for Momentary loudness  (M), and Integrated loudness (I)
  
      struct integrator i3000;        ///&lt;    3s integrator, used for Short term loudness (S), and Loudness Range      (LRA)
  
  
  
      /* I and LRA specific */
  
      double integrated_loudness;     ///&lt; integrated loudness in LUFS (I)
  
      double loudness_range;          ///&lt; loudness range in LU (LRA)
  
      double lra_low, lra_high;       ///&lt; low and high LRA values
  
  
  
      /* misc */
  
      int loglevel;                   ///&lt; log level for frame logging
  
      int metadata;                   ///&lt; whether or not to inject loudness results in frames
  
      int dual_mono;                  ///&lt; whether or not to treat single channel input files as dual-mono
  
      double pan_law;                 ///&lt; pan law value used to calculate dual-mono measurements
  
      int target;                     ///&lt; target level in LUFS used to set relative zero LU in visualization
  
      int gauge_type;                 ///&lt; whether gauge shows momentary or short
  
      int scale;                      ///&lt; display scale type of statistics
  
  } EBUR128Context;
  
  
  
  void dump_ebur128_context(void *priv);
  
  
  
  static int open_input_file(const char *filename)
  
  {
  
      int ret;
  
      AVCodec *dec;
  
  
  
      if ((ret = avformat_open_input(&amp;fmt_ctx, filename, NULL, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
  
          return ret;
  
      }
  
  
  
      if ((ret = avformat_find_stream_info(fmt_ctx, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
  
          return ret;
  
      }
  
  
  
      /* select the audio stream */
  
      ret = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_AUDIO, -1, -1, &amp;dec, 0);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot find an audio stream in the input file\n");
  
          return ret;
  
      }
  
      audio_stream_index = ret;
  
  
  
      /* create decoding context */
  
      dec_ctx = avcodec_alloc_context3(dec);
  
      if (!dec_ctx)
  
          return AVERROR(ENOMEM);
  
      avcodec_parameters_to_context(dec_ctx, fmt_ctx->streams[audio_stream_index]->codecpar);
  
  
  
      /* init the audio decoder */
  
      if ((ret = avcodec_open2(dec_ctx, dec, NULL)) &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot open audio decoder\n");
  
          return ret;
  
      }
  
  
  
      return 0;
  
  }
  
  
  
  static int init_filters(const char *filters_descr)
  
  {
  
      char args[512];
  
      int ret = 0;
  
      const AVFilter *abuffersrc  = avfilter_get_by_name("abuffer");
  
      const AVFilter *abuffersink = avfilter_get_by_name("abuffersink");
  
      AVFilterInOut *outputs = avfilter_inout_alloc();
  
      AVFilterInOut *inputs  = avfilter_inout_alloc();
  
      static const enum AVSampleFormat out_sample_fmts[] = { AV_SAMPLE_FMT_S16, -1 };
  
      static const int64_t out_channel_layouts[] = { AV_CH_LAYOUT_MONO, -1 };
  
      static const int out_sample_rates[] = { 8000, -1 };
  
      const AVFilterLink *outlink;
  
      AVRational time_base = fmt_ctx->streams[audio_stream_index]->time_base;
  
  
  
      filter_graph = avfilter_graph_alloc();
  
      if (!outputs || !inputs || !filter_graph) {
  
          ret = AVERROR(ENOMEM);
  
          goto end;
  
      }
  
  
  
      /* buffer audio source: the decoded frames from the decoder will be inserted here. */
  
      if (!dec_ctx->channel_layout)
  
          dec_ctx->channel_layout = av_get_default_channel_layout(dec_ctx->channels);
  
      snprintf(args, sizeof(args),
  
              "time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
  
               time_base.num, time_base.den, dec_ctx->sample_rate,
  
               av_get_sample_fmt_name(dec_ctx->sample_fmt), dec_ctx->channel_layout);
  
      ret = avfilter_graph_create_filter(&amp;buffersrc_ctx, abuffersrc, "in",
  
                                         args, NULL, filter_graph);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
  
          goto end;
  
      }
  
  
  
      /* buffer audio sink: to terminate the filter chain. */
  
      ret = avfilter_graph_create_filter(&amp;buffersink_ctx, abuffersink, "out",
  
                                         NULL, NULL, filter_graph);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
  
          goto end;
  
      }
  
  
  
      ret = av_opt_set_int_list(buffersink_ctx, "sample_fmts", out_sample_fmts, -1,
  
                                AV_OPT_SEARCH_CHILDREN);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
  
          goto end;
  
      }
  
  
  
      ret = av_opt_set_int_list(buffersink_ctx, "channel_layouts", out_channel_layouts, -1,
  
                                AV_OPT_SEARCH_CHILDREN);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
  
          goto end;
  
      }
  
  
  
      ret = av_opt_set_int_list(buffersink_ctx, "sample_rates", out_sample_rates, -1,
  
                                AV_OPT_SEARCH_CHILDREN);
  
      if (ret &lt; 0) {
  
          av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
  
          goto end;
  
      }
  
  
  
      /*
  
       * Set the endpoints for the filter graph. The filter_graph will
  
       * be linked to the graph described by filters_descr.
  
       */
  
  
  
      /*
  
       * The buffer source output must be connected to the input pad of
  
       * the first filter described by filters_descr; since the first
  
       * filter input label is not specified, it is set to "in" by
  
       * default.
  
       */
  
      outputs->name       = av_strdup("in");
  
      outputs->filter_ctx = buffersrc_ctx;
  
      outputs->pad_idx    = 0;
  
      outputs->next       = NULL;
  
  
  
      /*
  
       * The buffer sink input must be connected to the output pad of
  
       * the last filter described by filters_descr; since the last
  
       * filter output label is not specified, it is set to "out" by
  
       * default.
  
       */
  
      inputs->name       = av_strdup("out");
  
      inputs->filter_ctx = buffersink_ctx;
  
      inputs->pad_idx    = 0;
  
      inputs->next       = NULL;
  
  
  
      if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,
  
                                          &amp;inputs, &amp;outputs, NULL)) &lt; 0)
  
          goto end;
  
  
  
      if ((ret = avfilter_graph_config(filter_graph, NULL)) &lt; 0)
  
          goto end;
  
  
  
      /* Print summary of the sink buffer
  
       * Note: args buffer is reused to store channel layout string */
  
      outlink = buffersink_ctx->inputs[0];
  
      av_get_channel_layout_string(args, sizeof(args), -1, outlink->channel_layout);
  
      av_log(NULL, AV_LOG_INFO, "Output: srate:%dHz fmt:%s chlayout:%s\n",
  
             (int)outlink->sample_rate,
  
             (char *)av_x_if_null(av_get_sample_fmt_name(outlink->format), "?"),
  
             args);
  
  
  
  end:
  
      avfilter_inout_free(&amp;inputs);
  
      avfilter_inout_free(&amp;outputs);
  
  
  
      return ret;
  
  }
  
  
  
  static void print_frame(const AVFrame *frame)
  
  {
  
  //    const int n = frame->nb_samples * av_get_channel_layout_nb_channels(frame->channel_layout);
  
  //    const uint16_t *p     = (uint16_t*)frame->data[0];
  
  //    const uint16_t *p_end = p + n;
  
  //
  
  //    while (p &lt; p_end) {
  
  //        fputc(*p    &amp; 0xff, stdout);
  
  //        fputc(*p>>8 &amp; 0xff, stdout);
  
  //        p++;
  
  //    }
  
  //    fflush(stdout);
  
  }
  
  
  
  int main(int argc, char **argv)
  
  {
  
      av_log_set_level(AV_LOG_DEBUG);
  
      int ret;
  
      AVPacket packet;
  
      AVFrame *frame = av_frame_alloc();
  
      AVFrame *filt_frame = av_frame_alloc();
  
  
  
      if (!frame || !filt_frame) {
  
          perror("Could not allocate frame");
  
          exit(1);
  
      }
  
  
  
  
  
      if ((ret = open_input_file(argv[1])) &lt; 0)
  
          goto end;
  
      if ((ret = init_filters(filter_descr)) &lt; 0)
  
          goto end;
  
  
  
      /* read all packets */
  
      while (1) {
  
          if ((ret = av_read_frame(fmt_ctx, &amp;packet)) &lt; 0)
  
              break;
  
  
  
          if (packet.stream_index == audio_stream_index) {
  
              ret = avcodec_send_packet(dec_ctx, &amp;packet);
  
              if (ret &lt; 0) {
  
                  av_log(NULL, AV_LOG_ERROR, "Error while sending a packet to the decoder\n");
  
                  break;
  
              }
  
  
  
              while (ret >= 0) {
  
                  ret = avcodec_receive_frame(dec_ctx, frame);
  
                  if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF) {
  
                      break;
  
                  } else if (ret &lt; 0) {
  
                      av_log(NULL, AV_LOG_ERROR, "Error while receiving a frame from the decoder\n");
  
                      goto end;
  
                  }
  
  
  
                  if (ret >= 0) {
  
                      /* push the audio data from decoded frame into the filtergraph */
  
                      if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) &lt; 0) {
  
                          av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
  
                          break;
  
                      }
  
  
  
                      /* pull filtered audio from the filtergraph */
  
                      while (1) {
  
                          ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
  
                          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
                              break;
  
                          if (ret &lt; 0)
  
                              goto end;
  
                          print_frame(filt_frame);
  
                          av_frame_unref(filt_frame);
  
                      }
  
                      av_frame_unref(frame);
  
                  }
  
              }
  
          }
  
          av_packet_unref(&amp;packet);
  
      }
  
      if(filter_graph->nb_filters){
  
      av_log(filter_graph, AV_LOG_INFO, "hello : %d \n",
  
                  filter_graph->nb_filters);
  
      int i;
  
      for (int i = 0; i &lt; filter_graph->nb_filters; i++){
  
          av_log(filter_graph, AV_LOG_INFO, "name : %s \n",
  
                          filter_graph->filters[i]->name);
  
      }
  
      }
  
  
  
      av_log(filter_graph, AV_LOG_INFO, "name : %s \n",
  
                              filter_graph->filters[2]->name);
  
      void* priv = filter_graph->filters[2]->priv;
  
  
  
      dump_ebur128_context(&amp;priv);
  
  
  
  end:
  
  
  
  
  
      avfilter_graph_free(&amp;filter_graph);
  
      avcodec_free_context(&amp;dec_ctx);
  
      avformat_close_input(&amp;fmt_ctx);
  
      av_frame_free(&amp;frame);
  
      av_frame_free(&amp;filt_frame);
  
  
  
      if (ret &lt; 0 &amp;&amp; ret != AVERROR_EOF) {
  
          fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
  
          exit(1);
  
      }
  
  
  
      exit(0);
  
  }
  
  
  
  void dump_ebur128_context(void *priv){
  
      EBUR128Context *ebur128 = priv;
  
  
  
      av_log(ebur128, AV_LOG_INFO, "integrated_loudness : %5.1f \n",
  
                              ebur128->integrated_loudness);
  
      av_log(ebur128, AV_LOG_INFO, "lra_low : %5.1f \n",
  
                                  ebur128->lra_low);
  
      av_log(ebur128, AV_LOG_INFO, "lra_high : %5.1f \n",
  
                                  ebur128->lra_high);
  
  
  
  
  
  }

  program fails while accessing integrated loudness in dump_ebur128_context.

  can someone guide me about , how I should proceed in here.

• How to analyse 404 pages

  1er juillet 2019, par Matomo Core Team — Development, Plugins

  How to analyse “not found” pages (404) in digital analytics

  Have you ever sent out a newsletter and one link wasn’t active yet ? Would you like to know how many users get affected when this happens ? Would you like to know if your visitors are encountering 404 pages ? 

  In this article we’re describing an easy way to analyse “not found” pages on your website with Matomo to increase your visitors’ user experience, user acquisition, and SEO (search engine optimization).

  How to know the number of 404s on my website ?

  There are different ways to get this information. Depending on how your website is built, you may or may not collect this data.

  The easiest way to answer this question is to fire a 404 page on your website, you do this by accessing a wrong url :

  

  As you can see here, in our case, the page title starts with “Page non trouvée” which stands for “Page not found” when translated in English (as the website we are considering here is in French) :

  

  In this example 19 page views have been fired and it generated a bounce rate of 67%. As a result ⅔ of the visits ended here.

  In some cases, the information related to a “not found” page can be found either within the title or within the URL, as some websites redirect you to a specific web page when a page can’t be found.

  If you can’t identify “not found” pages via a page title or a page URL, we strongly advise you to use this specific tracking code method on your 404 page : “How to track error pages in Matomo ?”. 

  You can easily set it with Matomo Tag Manager with a custom HTML tag :

  

  where the trigger is the following :

  

  You will however, have to define this trigger as an exclusion for all the other tags which may conflict with it (here below is the new trigger defined for the generic Matomo tags we are inserting on all pages) :

  

  Once this specific tracking is set, you will be able to track the source of the 404 and will gather all the “not found” pages in a specific group within your Page Title report :

  

  Here, for example, you can identify that the homepage of this website had a link pointing to a 404, in our case it was https://www.webassoc.org/pro-du-web.

  Note that this is just one technique. You could also create a custom dimension report and decide to send the 404 there also.

  How to get notified when a 404 page is visited ?

  Trust us, you’re not going to check everyday whether a 404 page has been visited. In order to avoid checking it manually, you can define custom alerts.

  There are three possible scenarios when “not found” pages can be fired :

  • internal 404 : one link within your website is pointing to a wrong url on the same website.
  • external 404 : someone from an external website made a link to yours and the link is not correct.
  • direct access 404 : someone access directly to a not found page on your website.

  You can define all those three within Matomo, but in your case, you will only have to focus on the first two only. In fact, you can’t really fix the third scenario. That’s the reason why we’re not focusing on it. It would result in irrelevant alerts.

  Custom alert for internal 404

  An internal 404 is defined from a 404 where the source is an internal web page. As a result, it will look like the following in your report :

  

  In this example, we’re using this specific custom implementation, the title of the page will contain “From = https://www.webassoc.org/”. So set our custom alert accordingly :

  

  Now every time a 404 page will be fired from an internal page, you’ll be notified by email.

  Note that you can also decide to not receive any email and track the evolution of alerts with the History of triggered alerts feature.

  Custom alert for external 404

  External 404 is almost the same setup. The only thing you need to keep in mind is that we want to exclude the 404 where the source is not indicated. As a result, your configuration will look like the following :

  

  Here your regular expression pattern is the following one :

  404/URL = .*From = (?!https://www.webassoc.org)[^\s]+

  as you’ll want to have any referrer coming from a website which is not Matomo and not a direct 404.

   

  You can now be notified every time that a 404 is fired from any link.

  Note that this configuration may slightly differ from website to website. So always double check your tracking code and the way the values are sent to your reports. Also try to trigger those alerts first before validating them.

  How to follow the evolution of your 404 over time ?

  It may be interesting to know how good or how bad you are performing in terms of 404.

  In order to check this information, you can click on the evolution icon near the 404 title :

  

  But you may be interested in accessing this information more regularly without having to create this report each time.

  So, one way to analyse the evolution of your 404 is to create a segment such as :

  

  and to click after that on evolution icon :

  

  As you can see below the number of “not found” pages is quite low in general, but we can also notice that a period received an increase in terms of 404 not found pages on May 27. It may be interesting to investigate it :

  

  You can start from the overview of referrers :

  

  As you can notice here the main source of 404 is coming from direct entries which is the most difficult channel to analyse as we don’t really know where the visitors are coming from.

  How to perform your analysis even faster ?

  As you can see analysing reports in Matomo in order to detect 404 pages is a time-consuming activity. In order to make it faster, you can already create a report about it within the Email reports feature with the following settings :

  • Segment : 404
  • Email schedule : never.
  • Visits summary and Page titles as selected report.

  You will then end up with a saved report listing all the URLs concerned :

  

  You can also have a look at the “Custom reports” premium feature.

  It will provide you with more flexibility. You will then be able to focus on the most important thing : the cause of 404.

  Good luck and happy analytics !