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• How to discover framebuffer width on android ?

  18 août 2013, par Guilherme Torres Castro

  i'm capturing framebuffer on my android device, but the decode is not working for the correctly resolution.

  I found i can get the bbp and screen resoution using :

  ioctl -rl 28 /dev/graphics/fb0 17920

  This command return :

  return buf : f0 00 00 00 40 01 00 00 f0 00 00 00 80 02 00 00 00 00 00 00 00 00 00 00 20 00 00 00

  In little-endian format i have :

  • The last four bytes (20) is the number of bbp 32.
  • The first four bytes is the screen width 0xF0 = 240
  • Bytes 5 to 8 is the screen height 0x0140 = 320

  I tried to decode the fb (Galaxy 5) using the folowing command :

  ./ffmpeg -vcodec rawvideo -f rawvideo -pix_fmt rgb32 -s 240x320 -i fb0 -f image2 -vcodec png image%d.png

  And i got this warning :

  Invalid buffer size, packet size 40960 < expected length 307200 Error
  while decoding stream #0:0 : Invalid argument

  and this two images :

  
  

  My raw file have 655.360 bytes but the correctly value expected is 614.400 bytes using this equation :

  fileSize = xres * yres * bpp/8 * numberOfFrames

  fileSize = 240 * 320 * 32/8 * 2 (android use double framebuffer) =
  614.400

  For my surprise i change width size on ffmpeg to 256 to match 655.360 bytes and worked (kind of, there are 16 extras pxs on the right side !
  I got the following images :

  
  

  So my question is WHY i have to use 256 width if my screen resolution is 240. And how to discovery this magic number for others resolutions.

• compile FFmpeg → Android { error : crtend_android.o : No such file or directory }

  22 mars 2013, par Jason Tsai

  I'm trying to complie FFmpeg on Android 4.0 (SAMSUNG GT-3113), and I meet an error when I try to get config.h and config.mak files.
  I'm using android-ndk-r8d and cygwin.

  The config.sh file which I created is followed :

  #!/bin/bash
  
   PREBUILT=${ndk}/toolchains/arm-linux-androideabi-4.7/prebuilt/windows
  
   PLATFORM=android-14
  
   ARCH=--arch=arm
  
   ./configure \
  
   ${ARCH} \
  
   --target-os=linux --enable-cross-compile --cross-prefix=${PREBUILT}/bin/arm-linux-androideabi- \
  
   --extra-cflags=" -fPIC -DANDROID -std=c99 " \
  
   --enable-version3 \
  
   --enable-gpl \
  
   --enable-nonfree \
  
   --disable-stripping \
  
   --disable-ffmpeg\
  
   --disable-ffplay\
  
   --disable-ffserver\
  
   --disable-ffprobe \
  
   --disable-encoders \
  
   --disable-muxers \
  
   --disable-devices \
  
   --disable-protocols \
  
   --enable-protocol=file \
  
   --enable-avfilter \
  
   --disable-network \
  
   --disable-avdevice \
  
   --disable-asm \
  
   --enable-neon \
  
   --enable-armv5te \
  
   --sysinclude=${ndk}/platforms/${PLATFORM}/arch-arm/usr/include \
  
   --extra-ldflags="-Wl,-rpath-link=${NDK_ROOT}/platforms/${PLATFORM}/arch-arm/usr/lib
  
  -L${ndk}/platforms/${PLATFORM}/arch-arm/usr/lib -nostdlib
  
  ${ndk}/platforms/${PLATFORM}/arch-arm/usr/lib/crtbegin_static.o
  
  ${ndk}/platforms/${PLATFORM}/arch-arm/usr/lib/crtend_android.o -lc -lm -ldl "

  After I run the config.sh with cygwin,it shows
  http://cygwin.com/cygwin-ug-net/using.html#using-pathnames/home/jason_tsai/android-ndk-r8d/toolchains/arm-linux-androideabi-4.7/prebuilt/windows/bin/arm-linux-androideabi-gcc is unable to create an executable file.C compiler test failed.

  I looked the logfile and it said
  arm-linux-androideabi-gcc.exe : error : /home/jason_tsai/android-ndk-r8d/platforms/android-14/arch-arm/usr/lib/crtend_android.o : No such file or directory
  C compiler test failed.

  I'm really very confusing.
  Any help will be appreciated. Thanks !!

• Separate Audio and Video in android

  13 février 2014, par Manoj

  I am beginner to Android application development,The aim of my project is to separate a audio and video from video file. after surfing in internet i came to know that, using FFmpeg we can do it.

  ffmpeg -i input.mkv # show stream numbers and formats
  
  ffmpeg -i input.mkv -c copy audio.m4a # AAC
  
  ffmpeg -i input.mkv -c copy audio.mp3 # MP3
  
  ffmpeg -i input.mkv -c copy audio.ac3 # AC3
  
  ffmpeg -i input.mkv -an -c copy video.mkv
  
  ffmpeg -i input.mkv -map 0:1 -c copy audio.m4a # stream 1

  separated video file wouldn't contain any audio it must be contain only video type.
  whether this option too possible in ffmpeg ?
  is any other alternative option there ?.