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• How to concatenate two AAC files smoothly ?

  15 août 2013, par James Deng

  To save time, I want to segment and transcode a large video file on multiple computers.

  I use ffmpeg to transcode the segments of the large video file with :

  ffmpeg -i large_movie.mp4 -ss 00:00:00 -t 00:01:00 -acodec libfaac seg0.flv
  
  ffmpeg -i large_movie.mp4 -ss 00:01:00 -t 00:01:00 -acodec libfaac seg1.flv
  
  ...

  And concatenate the segments with :

   ffmpeg -i concat.conf -vcodec copy -acodec copy result.flv

  The content of the concat.conf :

  ffsconcat version 1.0
  
  file seg0.flv
  
  file seg1.flv
  
  ...

  Now we get a result FLV file result.flv content all the segments. But when I play this file, I found the segment boundary audio may be momentarily interrupted ! I'm sure those segments is closely associated, and the timestamp is right.

  When I decode the AAC sample in segment file to a wave format, and open the wave with CoolEdit, I found at the front and the end of the file, the value of audio sample is very small (mute ?) ! At the front of the file, there is about 21ms 'mute' sample. And at the end of the file, there is about 3ms 'mute' sample.

  Is the mute samples result the momentarily interrupt ? How to concatenate media file containing AAC smoothly ?

  ---

  After further testing, I found if you split a wave file to small wave files, then encode this small wave files to small aac file use faac :

  faac -P -R 48000 -B 16 -C 2 -X -o 1.aac 1.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 2.aac 2.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 3.aac 3.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 4.aac 4.wav
  
  faac -P -R 48000 -B 16 -C 2 -X -o 5.aac 5.wav

  The console output like this :

  [hugeice@fedora19 trans]$ faac -P -R 48000 -B 16 -C 2 -X -o 5.aac 5.wav
  
  Freeware Advanced Audio Coder
  
  FAAC 1.28
  
  
  
  Quantization quality: 100
  
  Bandwidth: 16000 Hz
  
  Object type: Low Complexity(MPEG-2) + M/S
  
  Container format: Transport Stream (ADTS)
  
  Encoding 5.wav to 5.aac
  
     frame          | bitrate | elapsed/estim | play/CPU | ETA

  And concatenate this small aac files to a big aac files use :

  cat 1.aac 2.aac 3.aac 4.aac 5.aac > big.aac

  Now, if you play the big.aac, there is a momeniary interrupt at the segment boundary !

  The question becomes how segment coding and concatenate aac files smoothly ?

• Reverse Engineering Italian Literature

  1er juillet 2014, par Multimedia Mike — Reverse Engineering

  Some time ago, Diego “Flameeyes” Pettenò tried his hand at reverse engineering a set of really old CD-ROMs containing even older Italian literature. The goal of this RE endeavor would be to extract the useful literature along with any structural metadata (chapters, etc.) and convert it to a more open format suitable for publication at, e.g., Project Gutenberg or Archive.org.

  Unfortunately, the structure of the data thwarted the more simplistic analysis attempts (like inspecting for blocks of textual data). This will require deeper RE techniques. Further frustrating the effort, however, is the fact that the binaries that implement the reading program are written for the now-archaic Windows 3.1 operating system.

  In pursuit of this RE goal, I recently thought of a way to glean more intelligence using DOSBox.

  Prior Work
  There are 6 discs in the full set (distributed along with 6 sequential issues of a print magazine named L’Espresso). Analysis of the contents of the various discs reveals that many of the files are the same on each disc. It was straightforward to identify the set of files which are unique on each disc. This set of files all end with the extension “LZn”, where n = 1..6 depending on the disc number. Further, the root directory of each disc has a file indicating the sequence number (1..6) of the CD. Obviously, these are the interesting targets.

  The LZ file extensions stand out to an individual skilled in the art of compression– could it be a variation of the venerable LZ compression ? That’s actually unlikely because LZ — also seen as LIZ — stands for Letteratura Italiana Zanichelli (Zanichelli’s Italian Literature).

  The Unix ‘file’ command was of limited utility, unable to plausibly identify any of the files.

  Progress was stalled.

  Saying Hello To An Old Frenemy
  I have been showing this screenshot to younger coworkers to see if any of them recognize it :

  
  
  

  Not a single one has seen it before. Senior computer citizen status : Confirmed.

  I recently watched an Ancient DOS Games video about Windows 3.1 games. This episode showed Windows 3.1 running under DOSBox. I had heard this was possible but that it took a little work to get running. I had a hunch that someone else had probably already done the hard stuff so I took to the BitTorrent networks and quickly found a download that had the goods ready to go– a directory of Windows 3.1 files that just had to be dropped into a DOSBox directory and they would be ready to run.

  Aside : Running OS software procured from a BitTorrent network ? Isn’t that an insane security nightmare ? I’m not too worried since it effectively runs under a sandboxed virtual machine, courtesy of DOSBox. I suppose there’s the risk of trojan’d OS software infecting binaries that eventually leave the sandbox.

  Using DOSBox Like ‘strace’
  strace is a tool available on some Unix systems, including Linux, which is able to monitor the system calls that a program makes. In reverse engineering contexts, it can be useful to monitor an opaque, binary program to see the names of the files it opens and how many bytes it reads, and from which locations. I have written examples of this before (wow, almost 10 years ago to the day ; now I feel old for the second time in this post).

  Here’s the pitch : Make DOSBox perform as strace in order to serve as a platform for reverse engineering Windows 3.1 applications. I formed a mental model about how DOSBox operates — abstracted file system classes with methods for opening and reading files — and then jumped into the source code. Sure enough, the code was exactly as I suspected and a few strategic print statements gave me the data I was looking for.

  Eventually, I even took to running DOSBox under the GNU Debugger (GDB). This hasn’t proven especially useful yet, but it has led to an absurd level of nesting :

  
  
  

  The target application runs under Windows 3.1, which is running under DOSBox, which is running under GDB. This led to a crazy situation in which DOSBox had the mouse focus when a GDB breakpoint was triggered. At this point, DOSBox had all desktop input focus and couldn’t surrender it because it wasn’t running. I had no way to interact with the Linux desktop and had to reboot the computer. The next time, I took care to only use the keyboard to navigate the application and trigger the breakpoint and not allow DOSBox to consume the mouse focus.

  New Intelligence
  
  By instrumenting the local file class (virtual HD files) and the ISO file class (CD-ROM files), I was able to watch which programs and dynamic libraries are loaded and which data files the code cares about. I was able to narrow down the fact that the most interesting programs are called LEGGENDO.EXE (‘reading’) and LEGGENDA.EXE (‘legend’ ; this has been a great Italian lesson as well as RE puzzle). The first calls the latter, which displays this view of the data we are trying to get at :

  
  
  

  When first run, the program takes an interest in a file called DBBIBLIO (‘database library’, I suspect) :

  === Read(’LIZ98\DBBIBLIO.LZ1’) : req 337 bytes ; read 337 bytes from pos 0x0
  === Read(’LIZ98\DBBIBLIO.LZ1’) : req 337 bytes ; read 337 bytes from pos 0x151
  === Read(’LIZ98\DBBIBLIO.LZ1’) : req 337 bytes ; read 337 bytes from pos 0x2A2
  [...]
  

  While we were unable to sort out all of the data files in our cursory investigation, a few things were obvious. The structure of this file looked to contain 336-byte records. Turns out I was off by 1– the records are actually 337 bytes each. The count of records read from disc is equal to the number of items shown in the UI.

  Next, the program is interested in a few more files :

  *** isoFile() : ’DEPOSITO\BLOKCTC.LZ1’, offset 0x27D6000, 2911488 bytes large
  === Read(’DEPOSITO\BLOKCTC.LZ1’) : req 96 bytes ; read 96 bytes from pos 0x0
  *** isoFile() : ’DEPOSITO\BLOKCTX0.LZ1’, offset 0x2A9D000, 17152 bytes large
  === Read(’DEPOSITO\BLOKCTX0.LZ1’) : req 128 bytes ; read 128 bytes from pos 0x0
  === Seek(’DEPOSITO\BLOKCTX0.LZ1’) : seek 384 (0x180) bytes, type 0
  === Read(’DEPOSITO\BLOKCTX0.LZ1’) : req 256 bytes ; read 256 bytes from pos 0x180
  === Seek(’DEPOSITO\BLOKCTC.LZ1’) : seek 1152 (0x480) bytes, type 0
  === Read(’DEPOSITO\BLOKCTC.LZ1’) : req 32 bytes ; read 32 bytes from pos 0x480
  === Read(’DEPOSITO\BLOKCTC.LZ1’) : req 1504 bytes ; read 1504 bytes from pos 0x4A0
  [...]

  Eventually, it becomes obvious that BLOKCTC has the juicy meat. There are 32-byte records followed by variable-length encoded text sections. Since there is no text to be found in these files, the text is either compressed, encrypted, or both. Some rough counting (the program seems to disable copy/paste, which thwarts more precise counting), indicates that the text size is larger than the data chunks being read from disc, so compression seems likely. Encryption isn’t out of the question (especially since the program deems it necessary to disable copy and pasting of this public domain literary data), and if it’s in use, that means the key is being read from one of these files.

  Blocked On Disassembly
  So I’m a bit blocked right now. I know exactly where the data lives, but it’s clear that I need to reverse engineer some binary code. The big problem is that I have no idea how to disassemble Windows 3.1 binaries. These are NE-type executable files. Disassemblers abound for MZ files (MS-DOS executables) and PE files (executables for Windows 95 and beyond). NE files get no respect. It’s difficult (but not impossible) to even find data about the format anymore, and details are incomplete. It should be noted, however, the DOSBox-as-strace method described here lends insight into how Windows 3.1 processes NE-type EXEs. You can’t get any more authoritative than that.

  So far, I have tried the freeware version of IDA Pro. Unfortunately, I haven’t been able to get the program to work on my Windows machine for a long time. Even if I could, I can’t find any evidence that it actually supports NE files (the free version specifically mentions MZ and PE, but does not mention NE or LE).

  I found an old copy of Borland’s beloved Turbo Assembler and Debugger package. It has Turbo Debugger for Windows, both regular and 32-bit versions. Unfortunately, the normal version just hangs Windows 3.1 in DOSBox. The 32-bit Turbo Debugger loads just fine but can’t load the NE file.

  I’ve also wondered if DOSBox contains any advanced features for trapping program execution and disassembling. I haven’t looked too deeply into this yet.

  Future Work
  NE files seem to be the executable format that time forgot. I have a crazy brainstorm about repacking NE files as MZ executables so that they could be taken apart with an MZ disassembler. But this will take some experimenting.

  If anyone else has any ideas about ripping open these binaries, I would appreciate hearing them.

  And I guess I shouldn’t be too surprised to learn that all the literature in this corpus is already freely available and easily downloadable anyway. But you shouldn’t be too surprised if that doesn’t discourage me from trying to crack the format that’s keeping this particular copy of the data locked up.

• OpenCV and Network Cameras -or- How to spy on the neighbors ?

  16 mai 2014, par Alexander

  ---

  A bit of context ; this program was built originally to work with USB cameras - but because of the setup between where the cameras needs to be and where the computer is it makes more sense to switch to cameras run over a network. Now I’m trying to convert the program to accomplish this, but my efforts thus far have met with poor results. I’ve also asked this same question over on the OpenCV forums. Help me spy on my neighbors ! (This is with their permission, of course !) :D

  ---

  I’m using :

  • OpenCV v2.4.6.0
  • C++
  • D-Link Cloud Camera 7100 (Installer is DCS-7010L, according to the instructions.)

  ---

  I am trying to access the DLink camera’s video feed through OpenCV.

  I can access the camera through it’s IP address with a browser without any issues. Unfourtunately ; my program is less cooperative. When attempting to access the camera the program gives the OpenCV-generated error :

  warning : Error opening file (../../modules/highgui/src/cap_ffmpeg_impl.hpp:529)

  This error occurs with just about everything I try that doesn’t somehow generate more problems.

  For reference - the code in OpenCV’s cap_ffmpeg_impl.hpp around line 529 is as follows :

  522    bool CvCapture_FFMPEG::open( const char* _filename )
  
  523    {
  
  524        unsigned i;
  
  525        bool valid = false;
  
  526
  
  527        close();
  
  528
  
  529    #if LIBAVFORMAT_BUILD >= CALC_FFMPEG_VERSION(52, 111, 0)
  
  530        int err = avformat_open_input(&ic, _filename, NULL, NULL);
  
  531    #else
  
  532        int err = av_open_input_file(&ic, _filename, NULL, 0, NULL);
  
  533    #endif
  
  ...
  
  616    }

  ...for which I have no idea what I’m looking at. It seems to be looking for the ffmpeg version - but I’ve already installed the latest ffmpeg on that computer, so that shouldn’t be the issue.

  This is the edited down version I tried to use as per Sebastian Schmitz’s recommendation :

   1    #include <fstream>                            // File input/output
  
   2    #include <iostream>                           // cout / cin / etc
  
   3    #include                       // Windows API stuff
  
   4    #include                             // More input/output stuff
  
   5    #include <string>                         // "Strings" of characters strung together to form words and stuff
  
   6    #include <cstring>                            // "Strings" of characters strung together to form words and stuff
  
   7    #include <streambuf>                      // For buffering load files
  
   8    #include <array>                          // Functions for working with arrays
  
   9    #include <opencv2></opencv2>imgproc/imgproc.hpp>        // Image Processor
  
  10    #include <opencv2></opencv2>core/core.hpp>          // Basic OpenCV structures (cv::Mat, Scalar)
  
  11    #include <opencv2></opencv2>highgui/highgui.hpp>        // OpenCV window I/O
  
  12    #include "opencv2/calib3d/calib3d.hpp"
  
  13    #include "opencv2/features2d/features2d.hpp"
  
  14    #include "opencv2/opencv.hpp"
  
  15    #include "resource.h"                     // Included for linking the .rc file
  
  16    #include                             // For sleep()
  
  17    #include <chrono>                         // To get start-time of program.
  
  18    #include <algorithm>                      // For looking at whole sets.
  
  19
  
  20    #ifdef __BORLANDC__
  
  21      #pragma argsused
  
  22    #endif
  
  23
  
  24    using namespace std;                      // Standard operations. Needed for most basic functions.
  
  25    using namespace std::chrono;              // Chrono operations. Needed getting starting time of program.
  
  26    using namespace cv;                           // OpenCV operations. Needed for most OpenCV functions.
  
  27
  
  28    string videoFeedAddress = "";
  
  29    VideoCapture videoFeedIP = NULL;
  
  30    Mat clickPointStorage; //Artifact from original program.
  
  31
  
  32    void displayCameraViewTest()
  
  33    {
  
  34      VideoCapture cv_cap_IP;
  
  35      Mat color_img_IP;
  
  36      int capture;
  
  37      IplImage* color_img;
  
  38      cv_cap_IP.open(videoFeedAddress);
  
  39      Sleep(100);
  
  40      if(!cv_cap_IP.isOpened())
  
  41      {
  
  42          cout &lt;&lt; "Video Error: Video input will not work.\n";
  
  43          cvDestroyWindow("Camera View");
  
  44          return;
  
  45      }
  
  46      clickPointStorage.create(color_img_IP.rows, color_img_IP.cols, CV_8UC3);
  
  47      clickPointStorage.setTo(Scalar(0, 0, 0));
  
  48      cvNamedWindow("Camera View", 0); // create window
  
  49      IplImage* IplClickPointStorage = new IplImage(clickPointStorage);
  
  50      IplImage* Ipl_IP_Img;
  
  51      
  
  52      for(;;)
  
  53      {
  
  54          cv_cap_IP.read(color_img_IP);
  
  55          IplClickPointStorage = new IplImage(clickPointStorage);
  
  56          Ipl_IP_Img = new IplImage(color_img_IP);
  
  57          cvAdd(Ipl_IP_Img, IplClickPointStorage, color_img);
  
  58          cvShowImage("Camera View", color_img); // show frame
  
  59          capture = cvWaitKey(10); // wait 10 ms or for key stroke
  
  60          if(capture == 27 || capture == 13 || capture == 32){break;} // if ESC, Return, or space; close window.
  
  61      }
  
  62      cv_cap_IP.release();
  
  63      delete Ipl_IP_Img;
  
  64      delete IplClickPointStorage;
  
  65      cvDestroyWindow("Camera View");
  
  66      return;
  
  67    }
  
  68    
  
  69    int main()
  
  70    {
  
  71      while(1)
  
  72      {
  
  73          cout &lt;&lt; "Please Enter Video-Feed Address: ";
  
  74          cin >> videoFeedAddress;
  
  75          if(videoFeedAddress == "exit"){return 0;}
  
  76          cout &lt;&lt; "\nvideoFeedAddress: " &lt;&lt; videoFeedAddress &lt;&lt; endl;
  
  77          displayCameraViewTest();
  
  78          if(cvWaitKey(10) == 27){return 0;}
  
  79      }
  
  80      return 0;
  
  81    }
  
  </algorithm></chrono></array></streambuf></cstring></string></iostream></fstream>

  Using added ’cout’s I was able to narrow it down to line 38 : "cv_cap_IP.open(videoFeedAddress) ;"

  No value I enter for the videoFeedAddress variable seems to get a different result. I found THIS site that lists a number of possible addresses to connect to it. Since there exists no 7100 anywhere in the list & considering that the install is labeled "DCS-7010L" I used the addresses found next to the DCS-7010L listings. When trying to access the camera most of them can be reached through the browser, confirming that they reach the camera - but they don’t seem to affect the outcome when I use them in the videoFeedAddress variable.

  I’ve tried many of them both with and without username:password, the port number (554), and variations on ?.mjpg (the format) at the end.

  I searched around and came across a number of different "possible" answers - but none of them seem to work for me. Some of them did give me the idea for including the above username:password, etc stuff, but it doesn’t seem to be making a difference. Of course, the number of possible combinations is certainly rather large- so I certainly have not tried all of them (more direction here would be appreciated). Here are some of the links I found :

  1. This is one of the first configurations my code was in. No dice.
  2. This one is talking about files - not cameras. It also mentions codecs - but I wouldn’t be able to watch it in a web browser if that were the problem, right ? (Correct me if I’m wrong here...)
  3. This one has the wrong error code/points to the wrong line of code !
  4. This one mentions compiling OpenCV with ffmpeg support - but I believe 2.4.6.0 already comes with that all set and ready ! Otherwise it’s not that different from what I’ve already tried.
  5. Now THIS one appears to be very similar to what I have, but the only proposed solution doesn’t really help as I had already located a list of connections. I do not believe this is a duplicate, because as per THIS meta discussion I had a lot more information and so didn’t feel comfortable taking over someone else’s question - especially if I end up needing to add even more information later.

  Thank you for reading this far. I realize that I am asking a somewhat specific question - although I would appreciate any advice you can think of regarding OpenCV & network cameras or even related topics.

  ---

  TLDR : Network Camera and OpenCV are not cooperating. I’m unsure if
  it’s the address I’m using to direct the program to the camera or the
  command I’m using - but no adjustment I make seems to improve the
  result beyond what I’ve already done ! Now my neighbors will go unwatched !