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• lavf/concatdec : define "ffcat" and "ffconcat" extensions

  21 février 2013, par Stefano Sabatini

  lavf/concatdec : define "ffcat" and "ffconcat" extensions

• Cannot open ".mp4" video files using OpenCV 2.4.3, Python 2.7 in Windows 7 machine

  28 décembre 2015, par tjmonsi

  I am currently working on a project that involves reading mp4 video files.
  The problem I encountered is that it using Python 2.7 (32 bit), OpenCV 2.4.3 (cv2.pyd) in a Windows 7 machine.

  The code snippet is as follows :

  try:
  
          video = cv2.VideoCapture("video.mp4")
  
  except:
  
          print "Could not open video file"
  
          raise
  
  print video.grab()

  "video.grab()" always returns false : meaning it doesn’t read the file "video.mp4"
  But when we try this :

  try:
  
          video = cv2.VideoCapture("video.avi")
  
  except:
  
          print "Could not open video file"
  
          raise
  
  print video.grab()

  "video.grab()" returns true : meaning it is able to read ".avi" files.

  Another is we have tried this same snippet on Linux and Mac and it seems to work fine, meaning it is able to read both mp4 files and avi files.

  This problem is similar to this problem and this problem. Both still don’t have a clear and workable answer.

  I would appreciate any help or workaround aside from just using Linux or Mac for programming this as I need this to work on all three systems.

• NDK r8c warning for asm objects regarding "Cortex-A8 erratum" - should I be worried ?

  7 décembre 2012, par Alex Cohn

  Question : What is the meaning of this warning ? If there are no real-life consequences, I can live with it for a while... But I am concerned with what will happen if our program gets loaded on one of the faulty chips.

  Background : With NDK r8c, linking of X264 encoder issues warnings :

  cannot scan executable section 1 of libx264.a(dct-a.o) for Cortex-A8 erratum because it has no mapping symbols

  ... same warning for all assembly files in libx264.

  libx264.a itself was cross-compiled on the same machine with the same 4.6 toolchain taken from NDK.

  Here are the instructions to easily reproduce the problem (Ubuntu or MacOS) :

  1. Download x264-snapshot-20121203-2245 from ftp://ftp.videolan.org/pub/x264/snapshots/last_x264.tar.bz2

  2. Run ./configure --enable-pic --enable-strip --enable-static --cross-prefix=~/android-ndk-r8c/toolchains/arm-linux-androideabi-4.6/prebuilt/linux-x86/bin/arm-linux-androideabi- --sysroot=~/android-ndk-r8c/platforms/android-14/arch-arm --host=arm-linux

  3. Run ~/android-ndk-r8c/prebuilt/linux-x86/bin/make

  It will build the static library, and after that display the Cortex-A8 warning while linking the x265 executable. I am not worried about the compiler warnings, because building libx264.a is done offline, it is not part of our official daily build.

  I have reported this as http://code.google.com/p/android/issues/detail?id=40794.

  I tried to add the mapping symbols manually to dct-a.S following the ARM.com instructions, but this had no effect.