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• Capturing video over USB/HDMI/Thunderbolt

  12 novembre 2016, par Yatko

  Looking for a solution for capturing video over USB/HDMI/Thunderbolt from a digital output (e.g. digital camera) to a computer, Mac and/or Windows.

  The goal is to have an URL to a real-time video stream (e.g. IP/PATH/ ?.mp4) that we can further process/transcode/send to a media server.

  I’m looking for tips and ideas -similar to the method below-, maybe someone met a new project that’s focusing on capture-cards and devices, that does’n need a custom FFmpeg build. Something different.

  • we can capture the HDMI stream form a GoPro, using a Blackmagic Intensity Shuttle and DeckLink SDK with custom FFmpeg build using --extra-cflags and --extra-ldflags and the rest is straightforward

  Is there any tool, open-source project, something that’s made for this purpose ? Maybe something that also supports the Elgato Game Capture HD60 as well ? Any experimental projects for capturing and processing the incoming video over USB/HDMI/Thunderbolt ?

  The ultimate goal is live streaming to Wowza, using Cameleon live and a Sony Alpha a7S.

• Brute Force Dimensional Analysis

  15 juillet 2010, par Multimedia Mike — Game Hacking, Python

  I was poking at the data files of a really bad (is there any other kind ?) interactive movie video game known simply by one letter : D. The Sega Saturn version of the game is comprised primarily of Sega FILM/CPK files, about which I wrote the book. The second most prolific file type bears the extension ’.dg2’. Cursory examination of sample files revealed an apparently headerless format. Many of the video files are 288x144 in resolution. Multiplying that width by that height and then doubling it (as in, 2 bytes/pixel) yields 82944, which happens to be the size of a number of these DG2 files. Now, if only I had a tool that could take a suspected raw RGB file and convert it to a more standard image format.

  Here’s the FFmpeg conversion recipe I used :

   ffmpeg -f rawvideo -pix_fmt rgb555 -s 288x144 -i raw_file -y output.png
  

  So that covers the files that are suspected to be 288x144 in dimension. But what about other file sizes ? My brute force approach was to try all possible dimensions that would yield a particular file size. The Python code for performing this operation is listed at the end of this post.

  It’s interesting to view the progression as the script compresses to different sizes :

  
  
  

  That ’D’ is supposed to be red. So right away, we see that rgb555(le) is not the correct input format. Annoyingly, FFmpeg cannot handle rgb555be as a raw input format. But this little project worked well enough as a proof of concept.

  If you want to toy around with these files (and I know you do), I have uploaded a selection at : http://multimedia.cx/dg2/.

  Here is my quick Python script for converting one of these files to every acceptable resolution.

  work-out-resolution.py :
  

  PLAIN TEXT

  PYTHON :

  1. # !/usr/bin/python
  2.  
  3. import commands
  4. import math
  5. import os
  6. import sys
  7.  
  8. FFMPEG = "/path/to/ffmpeg"
  9.  
  10. def convert_file(width, height, filename) :
  11.  outfile = "%s-%dx%d.png" % (filename, width, height)
  12.  command = "%s -f rawvideo -pix_fmt rgb555 -s %dx%d -i %s -y %s" % (FFMPEG, width, height, filename, outfile)
  13.  commands.getstatusoutput(command)
  14.  
  15. if len(sys.argv) <2 :
  16.  print "USAGE : work-out-resolution.py <file>"
  17.  sys.exit(1)
  18.  
  19. filename = sys.argv[1]
  20. if not os.path.exists(filename) :
  21.  print filename + " does not exist"
  22.  sys.exit(1)
  23.  
  24. filesize = os.path.getsize(filename) / 2
  25.  
  26. limit = int(math.sqrt(filesize)) + 1
  27. for i in xrange(1, limit) :
  28.  if filesize % i == 0 and filesize & 1 == 0 :
  29.   convert_file(i, filesize / i, filename)
  30.   convert_file(filesize / i, i, filename)

• vmd : decode videos with no LZ buffer size provided - they might not need it

  1er juin 2013, par Kostya Shishkov

  vmd : decode videos with no LZ buffer size provided - they might not need it
  The buffer is used for an additional pass of frame compression, so videos
  
  can be coded without ever using it (and some are coded so indeed, e.g. in
  
  Woodruff and the Schnibble of Azimuth game).
  

  • [DBH] libavcodec/vmdav.c