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• Subtitling Sierra RBT Files

  2 juin 2016, par Multimedia Mike — Game Hacking

  This is part 2 of the adventure started in my Subtitling Sierra VMD Files post. After I completed the VMD subtitling, The Translator discovered a wealth of animation files in a format called RBT (this apparently stands for “Robot” but I think “Ribbit” format could be more fun). What are we going to do ? We had come so far by solving the VMD subtitling problem for Phantasmagoria. It would be a shame if the effort ground to a halt due to this.

  Fortunately, the folks behind the ScummVM project already figured out enough of the format to be able to decode the RBT files in Phantasmagoria.

  In the end, I was successful in creating a completely standalone tool that can take a Robot file and a subtitle file and create a new Robot file with subtitles. The source code is here (subtitle-rbt.c). Here’s what the final result looks like :

  
  
  “What’s in the refrigerator ?” I should note at this juncture that I am not sure if this particular Robot file even has sound or dialogue since I was conducting these experiments on a computer with non-working audio.
  

  The RBT Format
  I have created a new MultimediaWiki page describing the Robot Animation format based on the ScummVM source code. I have not worked with a format quite like this before. These are paletted animations which consist of a sequence of independent frames that are designed to be overlaid on top of static background. Because of these characteristics, each frame encodes its own unique dimensions and origin coordinate within the frame. While the Phantasmagoria VMD files are usually 288×144 (which are usually double-sized for the benefit of a 640×400 Super VGA canvas), these frames are meant to be plotted on a game field that was roughly 576×288 (288×144 doublesized).
  

  For example, 2 minimalist animation frames from a desk investigation Robot file :

  
  
  100×147

  
  101×149
  

  As for compression, my first impression was that the algorithm was the same as VMD. This is wrong. It evidently uses an unmodified version of a standard algorithm called Lempel-Ziv-Stac (LZS). It shows up in several RFCs and was apparently used in MS-DOS’s transparent disk compression scheme.

  Approach
  Thankfully, many of the lessons I learned from the previous project are applicable to this project, including : subtitle library interfacing, subtitling in the paletted colorspace, and replacing encoded frames from the original file instead of trying to create a new file.

  Here is the pitch for this project :

  • Create a C program that can traverse through an input file, piece by piece, and generate an output file. The result of this should be a bitwise identical file.
  • Adapt the LZS compression decoding algorithm from ScummVM into the new tool. Make the tool dump raw Portable NetMap (PNM) files of varying dimensions and ensure that they look correct.
  • Compress using LZS.
  • Stretch the frames and draw subtitles.
  • More compression. Find the minimum window for each frame.

  Compression
  Normally, my first goal is to decompress the video and store the data in a raw form. However, this turned out to be mathematically intractable. While the format does support both compressed and uncompressed frames (even though ScummVM indicates that the uncompressed path is yet unexercised), the goal of this project requires making the frames so large that they overflow certain parameters of the file.

  A Robot file has a sequence of frames and 2 tables describing the size of each frame. One table describes the entire frame size (audio + video) while the second table describes just the video frame size. Since these tables only use 16 bits to specify a size, the maximum frame size is 65536 bytes. Leaving space for the audio portion of the frame, this only leaves a per-frame byte budget of about 63000 bytes for the video. Expanding the frame to 576×288 (165,888 pixels) would overflow this limit.

  Anyway, the upshot is that I needed to compress the data up front.

  Fortunately, the LZS compressor is pretty straightforward, at least if you have experience writing VLC-oriented codecs. While the algorithm revolves around back references, my approach was to essentially write an RLE encoder. My compressor would search for runs of data (plentiful when I started to stretch the frame for subtitling purposes). When a run length of n=3 or more of the same pixel is found, encode the pixel by itself, and then store a back reference of offset -1 and length (n-1). It took a little while to iron out a few problems, but I eventually got it to work perfectly.

  I have to say, however, that the format is a little bit weird in how it codes very large numbers. The length encoding is somewhat Golomb-like, i.e., smaller values are encoded with fewer bits. However, when it gets to large numbers, it starts encoding counts of 15 as blocks of 1111. For example, 24 is bigger than 7. Thus, emit 1111 into the bitstream and subtract 8 from 23 -> 16. Still bigger than 15, so stuff another 1111 into the bitstream and subtract 15. Now we’re at 1, so stuff 0001. So 24 is 11111111 0001. 12 bits is not too horrible. But the total number of bytes (value / 30). So a value of 300 takes around 10 bytes (80 bits) to encode.

  Palette Slices
  As in the VMD subtitling project, I took the subtitle color offered in the subtitle spec file as a suggestion and used Euclidean distance to match to the closest available color in the palette. One problem, however, is that the palette is a lot smaller in these animations. According to my notes, for the set of animations I scanned, only about 80 colors were specified, starting at palette index 55. I hypothesize that different slices of the palette are reserved for different uses. E.g., animation, background, and user interface. Thus, there is a smaller number of colors to draw upon for subtitling purposes.

  Scaling
  One bit of residual weirdness in this format is the presence of a per-frame scale factor. While most frames set this to 100 (100% scale), I have observed 70%, 80%, and 90%. ScummVM is a bit unsure about how to handle these, so I am as well. However, I eventually realized I didn’t really need to care, at least not when decoding and re-encoding the frame. Just preserve the scale factor. I intend to modify the tool further to take scale factor into account when creating the subtitle.

  The Final Resolution
  Right around the time that I was composing this post, The Translator emailed me and notified me that he had found a better way to subtitle the Robot files by modifying the scripts, rendering my entire approach moot. The result is much cleaner :

  
  
  Turns out that the engine supported subtitles all along
  

  It’s a good thing that I enjoyed the challenge or I might be annoyed at this point.

  See Also

  • Subtitling Sierra VMD Files : My effort to subtitle the main FMV files found in Sierra games.

• Unknown input format : 'rawvideo' when trying to save animation

  8 juin 2022, par John Klint

  So, I get a strange error trying to save animations created with matplotlib.FuncAnimation using FFMpegWriter.

  


  /home/j/PycharmProjects/venvtest/venv/bin/python /home/j/PycharmProjects/venvtest/main.py&#xA;MovieWriter stderr:&#xA;Unknown input format: &#x27;rawvideo&#x27;&#xA;&#xA;Traceback (most recent call last):&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 234, in saving&#xA;    yield self&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 1093, in save&#xA;    writer.grab_frame(**savefig_kwargs)&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 351, in grab_frame&#xA;    self.fig.savefig(self._proc.stdin, format=self.frame_format,&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/figure.py", line 3046, in savefig&#xA;    self.canvas.print_figure(fname, **kwargs)&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/backend_bases.py", line 2319, in print_figure&#xA;    result = print_method(&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/backend_bases.py", line 1648, in wrapper&#xA;    return func(*args, **kwargs)&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/_api/deprecation.py", line 415, in wrapper&#xA;    return func(*inner_args, **inner_kwargs)&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/backends/backend_agg.py", line 486, in print_raw&#xA;    fh.write(renderer.buffer_rgba())&#xA;BrokenPipeError: [Errno 32] Broken pipe&#xA;&#xA;During handling of the above exception, another exception occurred:&#xA;&#xA;Traceback (most recent call last):&#xA;  File "/home/j/PycharmProjects/venvtest/main.py", line 24, in <module>&#xA;    anim.save(&#x27;basic_animation.mp4&#x27;, writer=FFwriter)&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 1093, in save&#xA;    writer.grab_frame(**savefig_kwargs)&#xA;  File "/usr/lib/python3.9/contextlib.py", line 137, in __exit__&#xA;    self.gen.throw(typ, value, traceback)&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 236, in saving&#xA;    self.finish()&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 342, in finish&#xA;    self._cleanup()  # Inline _cleanup() once cleanup() is removed.&#xA;  File "/home/j/PycharmProjects/venvtest/venv/lib/python3.9/site-packages/matplotlib/animation.py", line 373, in _cleanup&#xA;    raise subprocess.CalledProcessError(&#xA;subprocess.CalledProcessError: Command &#x27;[&#x27;/usr/bin/ffmpeg&#x27;, &#x27;-f&#x27;, &#x27;rawvideo&#x27;, &#x27;-vcodec&#x27;, &#x27;rawvideo&#x27;, &#x27;-s&#x27;, &#x27;640x480&#x27;, &#x27;-pix_fmt&#x27;, &#x27;rgba&#x27;, &#x27;-r&#x27;, &#x27;5&#x27;, &#x27;-loglevel&#x27;, &#x27;error&#x27;, &#x27;-i&#x27;, &#x27;pipe:&#x27;, &#x27;-vcodec&#x27;, &#x27;h264&#x27;, &#x27;-pix_fmt&#x27;, &#x27;yuv420p&#x27;, &#x27;-y&#x27;, &#x27;basic_animation.mp4&#x27;]&#x27; returned non-zero exit status 1.&#xA;&#xA;Process finished with exit code 1&#xA;</module>

  


  I am confident it has nothing to do with the animation data, the error occurs even when I create a simple test animation :

  


  import numpy as np
from matplotlib import pyplot as plt
from matplotlib import animation
# plt.rcParams['animation.ffmpeg_path'] = '/usr/bin/ffmpeg'

fig = plt.figure()
ax = plt.axes(xlim=(0, 2), ylim=(-2, 2))
line, = ax.plot([], [], lw=2)


def init():
    line.set_data([], [])
    return line,


def animate(i):
    x = np.linspace(0, 2, 1000)
    y = np.sin(2 * np.pi * (x - 0.01 * i))
    line.set_data(x, y)
    return line,


anim = animation.FuncAnimation(fig, animate, init_func=init,
                           frames=200, interval=20, blit=True)

FFwriter = animation.FFMpegWriter()
anim.save('basic_animation.mp4', writer=FFwriter)


  


  I am currently using PyCharm in LinuxMint and I have a fairly new version of FFMpeg (4.2.4) installed. Given that FFMpeg complains about 'rawvideo' which as far as I understand it is just a bunch of images in series, it seems unlikely this has anything to do with codecs. If I run ffmpeg -formats, sure enough rawvideo is in the list.

  


  I have tried manually setting plt.rcParams, like in the commented line in the code above, with no success. I have also tried setting up both anaconda and venv environments, but I get the same error.
Annoyingly, I did not have this problem a few months ago when I was using Ubuntu. I have also verified that it works on my friends Ubuntu desktop, using the same simple venv as I set up for myself.

  


  Any ideas ?

  


  EDIT : I use the fish shell, if that is relevant...

  


  Well this is peculiar. If I start a terminal from within PyCharm and check supported formats, I get the following :

  


  (venv) ffmpeg -formats
ffmpeg version 4.3.4 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 11.3.0 (GCC)
  configuration: --prefix=/usr --libdir=/usr/lib/x86_64-linux-gnu --disable-debug --disable-doc --disable-static --enable-optimizations --enable-shared --disable-everything --enable-ffplay --enable-ffprobe --enable-gnutls --enable-libaom --enable-libdav1d --enable-libfdk-aac --enable-libmp3lame --enable-libfontconfig --enable-libfreetype --enable-libopus --enable-libpulse --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libwebp --enable-openal --enable-opengl --enable-sdl2 --enable-vulkan --enable-zlib --enable-libv4l2 --enable-libxcb --enable-vdpau --enable-vaapi --enable-encoder='ac3,alac,flac,libfdk_aac,g723_1,mp2,libmp3lame,libopus,libspeex,pcm_alaw,pcm_mulaw,pcm_f32le,pcm_s16be,pcm_s24be,pcm_s16le,pcm_s24le,pcm_s32le,pcm_u8,tta,libvorbis,wavpack,' --enable-encoder='ass,ffv1,libaom_av1,libvpx_vp8,libvpx_vp9,mjpeg_vaapi,rawvideo,theora,vp8_vaapi,libopenh264' --enable-decoder='adpcm_g722,alac,flac,g723_1,g729,libfdk_aac,libopus,libspeex,mp2,mp3,m4a,pcm_alaw,pcm_mulaw,pcm_f16le,pcm_f24le,pcm_f32be,pcm_f32le,pcm_f64be,pcm_f64le,pcm_s16be,pcm_s16be_planar,pcm_s24be,pcm_s16le,pcm_s16le_planar,pcm_s24le,pcm_s24le_planar,pcm_s32le,pcm_s32le_planar,pcm_s64be,pcm_s64le,pcm_s8,pcm_s8_planar,pcm_u8,pcm_u24be,pcm_u24le,pcm_u32be,pcm_u32le,tta,vorbis,wavpack,' --enable-decoder='ass,ffv1,mjpeg,mjpegb,libaom_av1,libdav1d,libvpx_vp8,libvpx_vp9,rawvideo,theora,vp8,vp9,libopenh264' --enable-encoder='bmp,gif,jpegls,png,tiff,webp,' --enable-decoder='bmp,gif,jpegls,png,tiff,webp,' --enable-hwaccel='vp8_vaapi,mjpeg_vaapi,' --enable-parser='aac,ac3,flac,mjpeg,mpegaudio,mpeg4video,opus,vp3,vp8,vp9,vorbis,' --enable-muxer='ac3,ass,flac,g722,gif,matroska,mp3,mpegvideo,rtp,ogg,opus,pcm_s16be,pcm_s16le,wav,webm,' --enable-demuxer='aac,ac3,ass,flac,g722,gif,image_jpeg_pipe,image_png_pipe,image_webp_pipe,matroska,mjpeg,mov,mp3,mpegvideo,ogg,pcm_mulaw,pcm_alaw,pcm_s16be,pcm_s16le,rtp,wav,' --enable-filter='crop,scale,overlay,amix,amerge,aresample,format,aformat,fps,transpose,pad,' --enable-protocol='crypto,file,pipe,rtp,srtp,rtsp,tcp,udp,unix,' --arch=x86_64 --enable-libopenh264
  libavutil      56. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
File formats:
 D. = Demuxing supported
 .E = Muxing supported
 --
 D  aac             raw ADTS AAC (Advanced Audio Coding)
 DE ac3             raw AC-3
 D  alaw            PCM A-law
 D  asf             ASF (Advanced / Active Streaming Format)
 DE ass             SSA (SubStation Alpha) subtitle
 DE flac            raw FLAC
 DE g722            raw G.722
 DE gif             CompuServe Graphics Interchange Format (GIF)
 D  jpeg_pipe       piped jpeg sequence
  E matroska        Matroska
 D  matroska,webm   Matroska / WebM
 D  mjpeg           raw MJPEG video
 D  mov,mp4,m4a,3gp,3g2,mj2 QuickTime / MOV
 DE mp3             MP3 (MPEG audio layer 3)
 D  mpegts          MPEG-TS (MPEG-2 Transport Stream)
 D  mpegvideo       raw MPEG video
 D  mulaw           PCM mu-law
 DE ogg             Ogg
  E opus            Ogg Opus
 D  png_pipe        piped png sequence
 D  rm              RealMedia
 DE rtp             RTP output
 DE s16be           PCM signed 16-bit big-endian
 DE s16le           PCM signed 16-bit little-endian
 D  sdp             SDP
 DE wav             WAV / WAVE (Waveform Audio)
  E webm            WebM
 D  webp_pipe       piped webp sequence



  


  As is evident, there is no support for 'rawvideo' in the list above ! Very strange indeed, I do not know which ffmpeg this list belongs to, perhaps it is a version integrated into matplotlib's animation class ?

  


  Anyway, if I uncomment the line setting the ffmpeg_path I am back at the old error. I did get it to work however, by changing the path from '/usr/bin/ffmpeg' to '/home/j/.conda/envs/venvtest/bin/ffmpeg'. Then I get the file to run, create the animation and save it. This works for my real files as well, which do not even run that particular conda-environment. They do not recognize or find the ffmpeg I have in /usr/bin though. I have no clue why but at least I have a workaround now.

  


  Final edit :
It is solved. It was flatpak's fault. Lesson is, don't use flatpak (or snap for that matter) to install Pycharm.

  


• Subtitling Sierra RBT Files

  2 juin 2016, par Multimedia Mike — Game Hacking

  This is part 2 of the adventure started in my Subtitling Sierra VMD Files post. After I completed the VMD subtitling, The Translator discovered a wealth of animation files in a format called RBT (this apparently stands for “Robot” but I think “Ribbit” format could be more fun). What are we going to do ? We had come so far by solving the VMD subtitling problem for Phantasmagoria. It would be a shame if the effort ground to a halt due to this.

  Fortunately, the folks behind the ScummVM project already figured out enough of the format to be able to decode the RBT files in Phantasmagoria.

  In the end, I was successful in creating a completely standalone tool that can take a Robot file and a subtitle file and create a new Robot file with subtitles. The source code is here (subtitle-rbt.c). Here’s what the final result looks like :

  
  
  “What’s in the refrigerator ?” I should note at this juncture that I am not sure if this particular Robot file even has sound or dialogue since I was conducting these experiments on a computer with non-working audio.
  

  The RBT Format
  I have created a new MultimediaWiki page describing the Robot Animation format based on the ScummVM source code. I have not worked with a format quite like this before. These are paletted animations which consist of a sequence of independent frames that are designed to be overlaid on top of static background. Because of these characteristics, each frame encodes its own unique dimensions and origin coordinate within the frame. While the Phantasmagoria VMD files are usually 288×144 (which are usually double-sized for the benefit of a 640×400 Super VGA canvas), these frames are meant to be plotted on a game field that was roughly 576×288 (288×144 doublesized).
  

  For example, 2 minimalist animation frames from a desk investigation Robot file :

  
  
  100×147

  
  101×149
  

  As for compression, my first impression was that the algorithm was the same as VMD. This is wrong. It evidently uses an unmodified version of a standard algorithm called Lempel-Ziv-Stac (LZS). It shows up in several RFCs and was apparently used in MS-DOS’s transparent disk compression scheme.

  Approach
  Thankfully, many of the lessons I learned from the previous project are applicable to this project, including : subtitle library interfacing, subtitling in the paletted colorspace, and replacing encoded frames from the original file instead of trying to create a new file.

  Here is the pitch for this project :

  • Create a C program that can traverse through an input file, piece by piece, and generate an output file. The result of this should be a bitwise identical file.
  • Adapt the LZS compression decoding algorithm from ScummVM into the new tool. Make the tool dump raw Portable NetMap (PNM) files of varying dimensions and ensure that they look correct.
  • Compress using LZS.
  • Stretch the frames and draw subtitles.
  • More compression. Find the minimum window for each frame.

  Compression
  Normally, my first goal is to decompress the video and store the data in a raw form. However, this turned out to be mathematically intractable. While the format does support both compressed and uncompressed frames (even though ScummVM indicates that the uncompressed path is yet unexercised), the goal of this project requires making the frames so large that they overflow certain parameters of the file.

  A Robot file has a sequence of frames and 2 tables describing the size of each frame. One table describes the entire frame size (audio + video) while the second table describes just the video frame size. Since these tables only use 16 bits to specify a size, the maximum frame size is 65536 bytes. Leaving space for the audio portion of the frame, this only leaves a per-frame byte budget of about 63000 bytes for the video. Expanding the frame to 576×288 (165,888 pixels) would overflow this limit.

  Anyway, the upshot is that I needed to compress the data up front.

  Fortunately, the LZS compressor is pretty straightforward, at least if you have experience writing VLC-oriented codecs. While the algorithm revolves around back references, my approach was to essentially write an RLE encoder. My compressor would search for runs of data (plentiful when I started to stretch the frame for subtitling purposes). When a run length of n=3 or more of the same pixel is found, encode the pixel by itself, and then store a back reference of offset -1 and length (n-1). It took a little while to iron out a few problems, but I eventually got it to work perfectly.

  I have to say, however, that the format is a little bit weird in how it codes very large numbers. The length encoding is somewhat Golomb-like, i.e., smaller values are encoded with fewer bits. However, when it gets to large numbers, it starts encoding counts of 15 as blocks of 1111. For example, 24 is bigger than 7. Thus, emit 1111 into the bitstream and subtract 8 from 23 -> 16. Still bigger than 15, so stuff another 1111 into the bitstream and subtract 15. Now we’re at 1, so stuff 0001. So 24 is 11111111 0001. 12 bits is not too horrible. But the total number of bytes (value / 30). So a value of 300 takes around 10 bytes (80 bits) to encode.

  Palette Slices
  As in the VMD subtitling project, I took the subtitle color offered in the subtitle spec file as a suggestion and used Euclidean distance to match to the closest available color in the palette. One problem, however, is that the palette is a lot smaller in these animations. According to my notes, for the set of animations I scanned, only about 80 colors were specified, starting at palette index 55. I hypothesize that different slices of the palette are reserved for different uses. E.g., animation, background, and user interface. Thus, there is a smaller number of colors to draw upon for subtitling purposes.

  Scaling
  One bit of residual weirdness in this format is the presence of a per-frame scale factor. While most frames set this to 100 (100% scale), I have observed 70%, 80%, and 90%. ScummVM is a bit unsure about how to handle these, so I am as well. However, I eventually realized I didn’t really need to care, at least not when decoding and re-encoding the frame. Just preserve the scale factor. I intend to modify the tool further to take scale factor into account when creating the subtitle.

  The Final Resolution
  Right around the time that I was composing this post, The Translator emailed me and notified me that he had found a better way to subtitle the Robot files by modifying the scripts, rendering my entire approach moot. The result is much cleaner :

  
  
  Turns out that the engine supported subtitles all along
  

  It’s a good thing that I enjoyed the challenge or I might be annoyed at this point.

  See Also

  • Subtitling Sierra VMD Files : My effort to subtitle the main FMV files found in Sierra games.

  The post Subtitling Sierra RBT Files first appeared on Breaking Eggs And Making Omelettes.