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• How to remove a configuration option in yocto ?

  17 août 2016, par Griffin

  I am trying to build ffmpeg for an arm chip. I am using yocto. My .bb file looks like

  SUMMARY = "FFMPEG"
  
  HOMEPAGE = "http://ffmpeg.org"
  
  
  
  LICENSE = "GPLv2"
  
  #LIC_FILES_CHKSUM = "file://COPYING.GPLv2"
  
  
  
  #SECTION = "net"
  
  #DEPENDS = "sqlite3-native glib-2.0 zlib libpcre spawn-fcgi fcgi"
  
  
  
  S = "${WORKDIR}/git"
  
  
  
  SRCREV = "${AUTOREV}"
  
  
  
  SRC_URI = "git://source.ffmpeg.org/ffmpeg.git;branch=release/2.8 \
  
          "
  
  
  
  
  
  PACKAGECONFIG[--build] = ""
  
  
  
  EXTRA_OECONF = " \
  
               --extra-ldflags=-static \
  
               --extra-cflags=-static \
  
               --disable-mipsfpu \
  
               --disable-mips32r2 \
  
               --disable-mipsdspr1 \
  
               --disable-mipsdspr2 \
  
               --enable-bzlib \
  
               --enable-zlib \
  
  "
  
  
  
  inherit autotools pkgconfig

  When I try to build. I am getting error Unknown option "—build=x86_64-linux". How do I remove a configuration flag from do_configure in yocto so that i could build ffmpeg. please help

• Use of the 'hash' command

  25 mars 2019, par Rob

  I’m working on a small app based on ffmpeg, and I read a tutorial made for ubuntu where they advise to use the command hash on the produced executable.

  I’m curious about that command, did you ever use it ? For which purpose ?

  When I run it in my source folder, I get this (once compiled)

  $ hash
  
  hits    command
  
     1    /usr/bin/strip
  
     1    /usr/local/bin/ffmpeg
  
     1    /usr/bin/svn
  
     4    /usr/local/bin/brew
  
     2    /usr/bin/git
  
     1    /bin/rm
  
     1    /bin/cat
  
     1    /usr/bin/ld
  
     1    /bin/sh
  
     4    /usr/bin/man
  
     5    /usr/bin/make
  
     4    /usr/bin/otool
  
    15    /bin/ls
  
     6    /usr/bin/open
  
     2    /usr/bin/clear

  Looks like a summary of my bash_history…

  When I run it on an executable file, I do not have lots of lines displayed, and nothing seems to changes in that application ?

  $ md5 ffserver
  
  MD5 (ffserver) = 2beac612e5efd6ee4a827ae0893ee338
  
  $ hash ffserver
  
  $ md5 ffserver
  
  MD5 (ffserver) = 2beac612e5efd6ee4a827ae0893ee338

  When I look for the man, it just says it’s a builtin function. Really useful :)

  It does work (let say exist) on Linux and on MacOSX.

• How would I assign multiple MMAP's from single file descriptor ?

  9 juin 2011, par Alex Stevens

  So, for my final year project, I'm using Video4Linux2 to pull YUV420 images from a camera, parse them through to x264 (which uses these images natively), and then send the encoded stream via Live555 to an RTP/RTCP compliant video player on a client over a wireless network. All of this I'm trying to do in real-time, so there'll be a control algorithm, but that's not the scope of this question. All of this - except Live555 - is being written in C. Currently, I'm near the end of encoding the video, but want to improve performance.

  To say the least, I've hit a snag... I'm trying to avoid User Space Pointers for V4L2 and use mmap(). I'm encoding video, but since it's YUV420, I've been malloc'ing new memory to hold the Y', U and V planes in three different variables for x264 to read upon. I would like to keep these variables as pointers to an mmap'ed piece of memory.

  However, the V4L2 device has one single file descriptor for the buffered stream, and I need to split the stream into three mmap'ed variables adhering to the YUV420 standard, like so...

  buffers[n_buffers].y_plane = mmap(NULL, (2 * width * height) / 3,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset);
  
  buffers[n_buffers].u_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 1) /
  
                                      sysconf(_SC_PAGE_SIZE));
  
  buffers[n_buffers].v_plane = mmap(NULL, width * height / 6,
  
                                      PROT_READ | PROT_WRITE, MAP_SHARED,
  
                                      fd, buf.m.offset +
  
                                      ((2 * width * height) / 3 + 
  
                                      width * height / 6 + 1) / 
  
                                      sysconf(_SC_PAGE_SIZE));

  Where "width" and "height" is the resolution of the video (eg. 640x480).

  From what I understand... MMAP seeks through a file, kind of like this (pseudoish-code) :

  fd = v4l2_open(...);
  
  lseek(fd, buf.m.offset + (2 * width * height) / 3);
  
  read(fd, buffers[n_buffers].u_plane, width * height / 6);

  My code is located in a Launchpad Repo here (for more background) :
  http://bazaar.launchpad.net/ alex-stevens/+junk/spyPanda/files (Revision 11)

  And the YUV420 format can be seen clearly from this Wiki illustration : http://en.wikipedia.org/wiki/File:Yuv420.svg (I essentially want to split up the Y, U, and V bytes into each mmap'ed memory)

  Anyone care to explain a way to mmap three variables to memory from the one file descriptor, or why I went wrong ? Or even hint at a better idea to parse the YUV420 buffer to x264 ? :P

  Cheers ! ^^