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• PKG_CONFIG_PATH can't be seen by configure

  23 mars 2019, par Hashim

  I’m using Cygwin to compile a MinGW version of FFmpeg (I already use Cygwin so it didn’t make sense to use anything else to build).

  I was originally getting an error that someone on the Doom9 forums suggested might be due to mixing MinGW-64 and Cygwin dependencies. I then compiled or sourced MinGW-64 versions of all of the required dependencies (as some dependencies could not be compiled with Cygwin alone), and FFmpeg still fails to configure, always with the same error.

  This error is always a variation of "package not found using pkg-config" - if libaom is enabled, I get :

  ERROR : aom >= 1.0.0 not found using pkg-config

  If I don’t add —enable-libaom in the configure script, I get :

  ERROR : libass not found using pkg-config

  I’m running the following on the command line, in a single shell, to compile FFmpeg :

  cd /ffmpeg_sources/ffmpeg && export PKG_CONFIG_PATH="/usr/local/lib/pkgconfig" && 
  
  ./configure --arch=x86_64 --cross-prefix=x86_64-w64-mingw32- --target-os=mingw32 \
  
  --prefix="/usr/local" \
  
  --extra-cflags="-I/usr/local/include -static" \
  
  --extra-ldflags="-L/usr/local/lib -static" \
  
  --pkg-config-flags="--static" \
  
  --extra-libs="-pthread -lm" \
  
  --enable-libaom \
  
  --enable-libass \
  
  --enable-libfdk-aac \
  
  --enable-libfreetype \
  
  --enable-libmp3lame \
  
  --enable-libopus \
  
  --enable-libvorbis \
  
  --enable-libvpx \
  
  --enable-libx264 \
  
  --enable-libx265 \
  
  --enable-gpl \
  
  --enable-nonfree \
  
  --enable-static  \
  
  --disable-shared && 
  
  make -j$(nproc) && 
  
  make install

  A similar question [here] indicates that it’s an issue with PKG_CONFIG_PATH not seeing the packages in /usr/local/lib/pkgconfig, but when I do :

  cd /ffmpeg_sources/ffmpeg && PKG_CONFIG_PATH="/usr/local/lib/pkgconfig" && pkg-config --exists --print-errors aom && echo $?

  ...it returns a 0, indicating aom.pc was found in the PKG_CONFIG_PATH - which either rules out an issue with PKG_CONFIG_PATH or makes it a very specific one in which only configure and make aren’t able to see PKG_CONFIG_PATH, despite being run from the same shell just a moment after.

  How can I resolve this ?

  ---

  EDIT

  I did some further investigation by looking into ffbuild/config.log, and noticed that it shows a warning :

  WARNING : x86_64-w64-mingw32-pkg-config not found, library detection
  may fail.

  However, doing apt-cyg search x86_64-w64-mingw32-pkg-config shows that particular package as being installed.

  Sure enough, in the /bin folder, there is an extensionless file called x86_64-w64-mingw32-pkg-config, with the following contents :

  #!/bin/sh
  
  exec pkgconf --personality=x86_64-w64-mingw32 $@

  I’ve also found the following related issues, in case they can help anyone else figure out what’s going on here :

  https://ffmpeg.org/pipermail/ffmpeg-devel/2012-June/126683.html

  Warning "i686-mingw32-pkg-config not found, library detection may fail" while cross compiling ffmpeg

  https://github.com/Microsoft/FFmpegInterop/issues/106

  https://gitlab.gnome.org/GNOME/librsvg/issues/239

  https://ffmpeg.zeranoe.com/forum/viewtopic.php?t=2041

• How to capture a layered window with transparency background properly ? (using BitBlt)

  25 octobre 2016, par Mitra M

  I want to capture a WPF window (WPF layered window) with transparency background.

  To do that I tried FFmpeg, But :

  1 - If I set AllowTransparency (this is a property of WPF window) to false ,I can capture the window by gdigrab (this is an ffmpeg device), but output has black background.(I don’t want black background)

  2 - If I set AllowTransparency to true then gdigrab won’t work. (get black frame only)

  I have read David’s nice article, he has said :

  if you use BitBlt to do this, you could “or in” the CAPTUREBLT flag if
  you wanted to capture windows that are layered

  The gdigrab uses BitBlt, this is gdigrab.c code snippet :

  /* Blit screen grab */
  
      if (!BitBlt(dest_hdc, 0, 0,
  
                  clip_rect.right - clip_rect.left,
  
                  clip_rect.bottom - clip_rect.top,
  
                  source_hdc,
  
                  clip_rect.left, clip_rect.top, SRCCOPY | CAPTUREBLT)) {
  
          WIN32_API_ERROR("Failed to capture image");
  
          return AVERROR(EIO);
  
      }

  You can see the flags . (SRCCOPY | CAPTUREBLT).

  Please tell me :

  1- Why the gdigrab can not capture a WPF window properly ?

  2 - What changes in this code should be done to do this ?

  (Sorry for my English, I used translate.google)

  Thanks

• Live video encoding using...?

  27 décembre 2013, par Basic

  I'm attempting to write a fairly simplistic application that will stream video/audio from a webcam to someone else across the internet (ala Skypebut with more control).

  There seems to be very little useful/relevant information on the subjectand what I can find is largely outdated. From my research so far, x264 seems to be the way to go as it offers an ultrafast option which is designed for this situation

  I'm able to turn on the webcam and receive a stream of images. I can also listen on an audio device and get samples.

  Where I'm failing is encoding that information in such a way as to be able to stream with a minimum of latency (from what I've read, 200ms delay is the goal for no obvious lag, including network latency - so let's aim for 100-150ms)

  Things I've tried

  ffmpeg

  This seems to be the most widely used option for encoding. I've had two real issues using it. Firstly, even using x264 with no look-aheads and the bare minimum buffers for stability, the delay seems to be on the order of 700ms using image2pipe. Secondly, it requires ffmpeg to be installed - being able to do this without an external dependency would be nice.

  VLC

  As with ffmpeg this requires an external program which is a negative. Even worse, I can't seem to get a latency of under 2 seconds which seems to increase over time. I've also only been able to get VLC to capture the camera itself rather than take a stream of images which means I don't get a chance to pre-process them.

  DirectShow

  I've seen a number of sites recommending using the windows direct show encoders but I haven't been able to find one that works at anything like real time. In fact, the only one I've managed to get going reliably is a Windows Media codec that has a massive latency and fairly large size.

  Other considerations

  None of the above address the problem of adding an audio stream to the video. I'm not sure if I should attempt to encode them together or send a separate stream alongside the video.

  In short, I've been Googling for a week or so now and haven't found a decent way to do this. Can someone please point me at a decent example/guide ?