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• OpenCV VideoWriter will not open

  21 février 2015, par ChrisC

  I’m having trouble instantiating and opening an OpenCV VideoWriter for recording video on a Raspberry Pi (Raspbian Weezy).

  My project is written in C++, but I’ve written a minimal Python program that demonstrates the problem.

  https://gist.github.com/chriscollins/11ff2f43852e1c93dae8

  Both my C++ code and the Python code above run without problem on my Windows machine. Sometimes the writer does not open, but that’s to be expected - I don’t have all of the listed codecs installed (the list of codecs comes from the Open CV source), but a good number of them work correctly. However, on a Raspberry Pi, both the C++ code and the Python code fail with the VideoWriter never being opened. In the above Python code, writer.isOpened() returns false for every single codec, when run on a Raspberry Pi.

  I’ve chowned the destination directory to the user I’m running the Python script as, and chmodded it to 777 so I don’t believe that it is a permissions problem. I think it may be connected with how I’ve installed OpenCV or some of its dependencies, but I’m not sure how to rectify it.

  The install process I’ve used is as follows :

  1. Update firmware/packages via rpi-update, apt-get update and apt-get upgrade.

  2. Install the following dependencies via apt-get :

     libjpeg8
libjpeg8-dev
libjpeg8-dbg
libjpeg-progs
ffmpeg
libavcodec-dev
libavcodec53
libavformat53
libavformat-dev
libgstreamer0.10-0-dbg
libgstreamer0.10-0
libgstreamer0.10-dev
libxine1-ffmpeg
libxine-dev
libxine1-bin
libunicap2
libunicap2-dev
swig
libv4l-0
libv4l-dev
python-numpy
libpython2.6
python-dev
python2.6-dev
libgtk2.0-dev

  3. Download and unzip http://sourceforge.net/projects/opencvlibrary/files/opencv-unix/2.4.9/opencv-2.4.9.zip to /root/opencv-2.4.9.

  4. cd /root/opencv-2.4.9 and run cmake -DCMAKE_BUILD_TYPE=RELEASE -DCMAKE_INSTALL_PREFIX=/usr/local -DBUILD_PERF_TESTS=OFF -DBUILD_opencv_gpu=OFF -DBUILD_opencv_ocl=OFF. Output of cmake is available at https://gist.github.com/chriscollins/d8060e03a6acd6d4336c

  5. make and make install from the same directory.

  Various other OpenCV functionality works correctly on the Raspberry Pi (in C++ or in Python) - e.g. viewing a webcam via VideoCapture, but I can’t get the VideoWriter to work. I’m tempted to try installing FFMPEG from source instead of via apt-get, but as make takes 5+ hours to run on a Raspberry Pi, I was hoping I’d find the answer here, rather than proceeding with a trial and error approach !

  Any advice on how to solve (or debug) this is appreciated.

  EDIT : Added output of cmake command (https://gist.github.com/chriscollins/d8060e03a6acd6d4336c)

• How to embed an MP4 inside a PDF ?

  19 août 2020, par malat

  I am a happy user of img2pdf. This tool does the minimal amount of work to put a series of JPEG 2000/JPEG/PNG images into a PDF "enveloppe". However I am now faced with a new challenge : embed a MP4 file into a PDF "enveloppe".

  


  I see that commercial tool can do it, as seen at :

  


  

  • Add audio, video, and interactive objects to PDFs

  


  


  Here is one such sample PDF file (no Flash required on windows in this sample) :

  


  

  • https://gitlab.com/agrahn/media9/-/issues/9#note_345903962
** https://gitlab.com/agrahn/media9/uploads/90fddd777e0ec514c39c924cd8d3b688/video_test.pdf

  


  


  It seems to have been introduced in ISO 32000-1 (PDF 1.7 Extension Level 5)

  


  I am looking for a solution which will use the Rich Media annotation inside the PDF stream.

  


  There are dozen of duplicated questions on superuser/stackoverflow, which all pretty much refer to imagemagick/convert command line tool. But in my case, convert expand the images into a multi-page PDF (which is not my desired behavior) :

  


  $ convert input.mp4 output.pdf
$ pdfinfo output.pdf 
Title:          out
Producer:       https://imagemagick.org
CreationDate:   Wed Aug 19 15:38:01 2020 CEST
ModDate:        Wed Aug 19 15:38:01 2020 CEST
Tagged:         no
UserProperties: no
Suspects:       no
Form:           none
JavaScript:     no
Pages:          1601
Encrypted:      no
Page size:      352 x 288 pts
Page rot:       0
File size:      534407296 bytes
Optimized:      no
PDF version:    1.3


  


  with :

  


  $ convert --version
Version: ImageMagick 6.9.10-23 Q16 x86_64 20190101 https://imagemagick.org
Copyright: © 1999-2019 ImageMagick Studio LLC
License: https://imagemagick.org/script/license.php
Features: Cipher DPC Modules OpenMP 
Delegates (built-in): bzlib djvu fftw fontconfig freetype jbig jng jpeg lcms lqr ltdl lzma openexr pangocairo png tiff webp wmf x xml zlib


  


  and

  


  $ file input.mp4 
input.mp4: ISO Media, MP4 Base Media v1 [IS0 14496-12:2003]
$ ffprobe -v quiet -print_format json  -show_streams input.mp4 | grep codec_long_name
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",


  


• Cracking Aztec Game Audio

  7 juin 2011, par Multimedia Mike — Game Hacking

  Here’s a mild multimedia-related reverse engineering challenge for you. It’s pretty straightforward for those skilled in the art.

  The Setup
  One side effect of running this ridiculously niche interest blog at the intersection of multimedia, reverse engineering, and game hacking is that people occasionally contact me for assistance on those very matters. So it was when one of my MobyGames peers asked if I can help to extract some music from a game called Aztec Wars. The game consists of 2 discs, each with a music.xbe file that contains multiple tunes and is hundreds of megabytes large.

  
  
  

  That’s all the data I received from the first email. At first I’m wondering what makes people think I have some magical insight into cracking these formats with such little information. Ordinarily, I would need to have the entire data file to work with and possibly the game binaries. But I didn’t want to ask him to upload hundreds of megabytes of data and I didn’t feel like downloading it ; commitment issues and all.

  But then I gathered a little confidence and remembered that the .xbe files are probably just Game Resource Archive Formats (GRAF) which are, traditionally, absurdly simple. I asked my colleague to send me a hexdump of the first kilobyte of one of the .xbe GRAFs ('hexdump -C -n 1024 music.xbe > file') as well as the total file size of the GRAF.

  The Hexdump
  The first music.xbe file is 192817376 bytes large. These are the first 1024 144 bytes (more than enough) :

  00000000  01 00 00 00 60 04 00 00  14 00 00 00 01 00 00 00  |....`...........|
  00000010  0d 00 00 00 48 00 00 00  94 39 63 01 1c a4 21 03  |....H....9c..¤ !.|
  00000020  7a d2 54 04 04 28 ad 05  d8 88 fd 06 d8 88 fd 06  |zÒT..(­.Ø.ý.Ø.ý.|
  00000030  2a 6e 46 08 2a 6e 46 08  2a 6e 46 08 2a 6e 46 08  |*nF.*nF.*nF.*nF.|
  00000040  50 13 2f 0a e0 28 7e 0b  52 49 46 46 44 39 63 01  |P./.à( .RIFFD9c.|
  00000050  57 41 56 45 66 6d 74 20  10 00 00 00 01 00 02 00  |WAVEfmt ........|
  00000060  44 ac 00 00 10 b1 02 00  04 00 10 00 64 61 74 61  |D¬...±......data|
  00000070  fc 13 63 01 00 00 00 00  00 00 00 00 00 00 00 00  |ü.c.............|
  00000080  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
  

  The Challenge
  Armed with only the information in the foregoing section, figure out a method for extracting all the audio files in that file and advise on their playback/conversion. Ideally, this method should require minimal effort from both you and the person on the other end of the conversation.

  The Resolution
  The reason I ask is because I came up with a solution but knew, deep down, that there must be a slightly easier way. How would you solve this ?

  The music files in question are now preserved on YouTube (until they see fit to remove them for one reason or another).