Recherche avancée

Sur d’autres sites (11944)

• 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 detects a videofile path when it does not exist

  17 novembre 2020, par Nejc Kejzar

  this is boggling my mind. I am using ffmpeg to compress videos within the following python script :

  


  import re
import os

kage = 'MH5'
year = '2020'
month = '11'
day = '10'

# Set output dir; create it if it doesn't exist yet
downsampled_video_dir = home_data_dir + f'piCamera/downsampled_videos/{kage}/{year}/{month}/{day}/'
Path(downsampled_video_dir).mkdir(parents=True, exist_ok=True)
    
for i, video in enumerate(videos):
        # Set ffmpeg video compression terminal command and output directory for downsampled videos
        video_name = re.findall('\d+_\d+.mp4', video)[0]
        ds_output = downsampled_video_dir + video_name
        compress_command = f"ffmpeg -i {video} -vf scale={video_res[0]}:-2 {ds_output}"
        
        # Run ffmpeg video compression
        os.system(compress_command)


  


  videos is a list of full video paths of the videos that I wish to compress, and ds_output is a full path of where to write the compressed video. video_res[0] contains the desired height of the video with the following -2 automatically calculating the width so that the aspect ratio is preserved.

  


  For some reason when running this, ffmpeg detects some of the videos in the output directory as already existing and asks if I wish to overwrite them. The videos of course aren't there yet, so when I pass y, ffmpeg complains that no such file exists. Here is an example output for one of the problematic videos :

  


  ffmpeg -y -i '/home/piCamera/MH4/2020/11/10/20201110_085451.mp4' -vf scale=400:300  '/home/piCamera/downsampled_videos/MH4/2020/11/10/20201110_085451.mp4'
ffmpeg version 4.2.4-1ubuntu0.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
  configuration: --prefix=/usr --extra-version=1ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/home/piCamera/MH4/2020/11/10/20201110_085451.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf58.20.100
  Duration: 00:03:58.84, start: 0.000000, bitrate: 1190 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 960x720, 1190 kb/s, 5 fps, 5 tbr, 10240 tbn, 20480 tbc (default)
    Metadata:
      handler_name    : VideoHandler
/home/piCamera/downsampled_videos/MH4/2020/11/10/20201110_085451.mp4: No such file or directory


  


  This happens with about 3 videos out of 53, the rest run normally. I've tried restarting the terminal, deleted the whole created downsampled_video_dir and run again, but no matter how many times I restart, the same videos are the problem. The only thing that appears to help is if I change the output directory name. Any ideas of why this strange error is happening ?

  


  This is being run on Ubuntu20 with python3.7.9 in a Jupyter Notebook.

  


  Many, many thanks for all the insights !

  


• How to concat videos with FFMPEG without a black frame in the middle

  21 juillet 2020, par david k

  I need to join two videos together programmatically, and FFMPEG seems to be working perfectly except it leaves a single black frame between the two joined videos.

  


  Based on this post, I'm guessing it's because the video and audio streams aren't exactly the same length (not sure why). Since I'm seeing a black flash, I'm guessing that the audio is slightly longer than the video, but I can't figure out how to remedy that. I'm fine losing a tiny piece of the audio at the end of the file.

  


  Can anyone help me "trim" the end of my audio stream so that it matches my video stream ? I need to be able to do this for many files, so I can't just hard-code a value into my command.

  


  I've attempted both of the methods that FFMPEG provides to concat, and both of them have this issue. I'd be fine with either approach, if I can get rid of the black frame.

  


  Transcode :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex \
  "[0:v][0:a][1:v][1:a] concat=n=2:v=1:a=1 [outv] [outa]" \
  -map "[outv]" -map "[outa]" output.mp4


  


  Re-wrap :

  


  ffmpeg -f concat -i files.txt -c copy output.mp4


  


  Here is the output of ffmpeg -i video1.mp4 -i video2.mp4 :

  


  ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple clang version 11.0.0 (clang-1100.0.33.16)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_1 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.0.1.jdk/Contents/Home/include/darwin -fno-stack-check' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video1.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2020-07-20T20:43:05.000000Z
  Duration: 00:00:09.88, start: 0.000000, bitrate: 1330 kb/s
    Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono, fltp, 53 kb/s (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:05.000000Z
      handler_name    : AAC audio
    Stream #0:1(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 1280x720, 1274 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:05.000000Z
      handler_name    : H.264/AVC video
      encoder         : AVC Coding
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'video2.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2020-07-20T20:43:06.000000Z
  Duration: 00:00:11.68, start: 0.000000, bitrate: 1346 kb/s
    Stream #1:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono, fltp, 53 kb/s (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:06.000000Z
      handler_name    : AAC audio
    Stream #1:1(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 1280x720, 1289 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:06.000000Z
      handler_name    : H.264/AVC video
      encoder         : AVC Coding
At least one output file must be specified