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• How do you compile FFmpeg for Windows (x86 and x64) using GCC/Clang for Windows ?

  31 juillet 2019, par cdlvcdlv

  There’s an in passing mention to GCC/Clang in the FFmpeg compiling guide.

  • If using GCC/Clang, consider adding -march=native to --extra-cflags to make slightly better use of your hardware.
    Alternatively, for a more general solution, examine the --arch and
    --cpu options. Gains are variable, and usually quite small. However,
    this is usually even more safe than the above, and is thus listed
    here.

  I found a guide to compile FFmpeg 4.0 for Android, for example, but none devoted to Windows builds.

  I’m interested in detailed answers explaining how you get to compile FFmpeg Windows builds for x86 and x64 using GCC/Clang for Windows or a successfully tested guide to it (which I didn’t find).

  Please include the way you must install every software needed. Needless to say, any other useful information should be in comments.

• avcodec_find_encoder(AV_CODEC_ID_H264) returns null

  22 janvier, par Monjura Rumi

  I am building an android application which will encode image captured from camera preview and later decode it. I am using ffmpeg library to encode and decode. To build static library with x264 I have used this tutorial. http://dl.dropbox.com/u/22605641/ffmpeg_android/main.html. As a source code of ffmpeg if I use the one downloaded from the link given in tutorial I can built it but can't build library if i use source code downloaded from here git clone git ://source.ffmpeg.org/ffmpeg.git ffmpeg. I have built library in ubuntu and using it in windows 7 in Eclipse. As I need only h264 encoder and decoder I have used following code for ffmpeg, slightly modified from tutorial.

  



  #!/bin/bash

NDK=~/Documents/android-ndk-r8e
PLATFORM=$NDK/platforms/android-8/arch-arm
PREBUILT=$NDK/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86
PREFIX=/home/android-ffmpeg

function build_one
{
    ./configure --target-os=linux --prefix=$PREFIX \
    --enable-cross-compile \
    --enable-runtime-cpudetect \
    --disable-asm \
    --arch=arm \
    --cc=$PREBUILT/bin/arm-linux-androideabi-gcc \
    --cross-prefix=$PREBUILT/bin/arm-linux-androideabi- \
    --disable-stripping \
    --nm=$PREBUILT/bin/arm-linux-androideabi-nm \
    --sysroot=$PLATFORM \
    --enable-nonfree \
    --enable-version3 \
    --disable-everything \
    --enable-gpl \
    --disable-doc \
    --enable-avresample \
    --disable-ffplay \
    --disable-ffserver \
    --enable-ffmpeg \
    --disable-ffprobe \
    --enable-avcodec \
    --enable-libx264 \
    --enable-encoder=libx264 \
    --enable-encoder=libx264rgb \
    --enable-decoder=h263 \
    --enable-decoder=h264 \
    --enable-decoder=svq3 \   
    --enable-zlib \
    --enable-gpl \
    --enable-pic \
    --disable-devices \
    --disable-avdevice \
    --extra-cflags="-I/home/android-ffmpeg/include -fPIC -DANDROID -D__thumb__ -mthumb -Wfatal-errors -Wno-deprecated -mfloat-abi=softfp -mfpu=vfpv3-d16 -marm -march=armv7-a" \
    --extra-ldflags="-L/home/android-ffmpeg/lib"
make -j4 install
$PREBUILT/bin/arm-linux-androideabi-ar d libavcodec/libavcodec.a inverse.o
$PREBUILT/bin/arm-linux-androideabi-ld -rpath-link=$PLATFORM/usr/lib -L$PLATFORM/usr/lib -L$PREFIX/lib  -soname libffmpeg.so -shared -nostdlib  -z,noexecstack -Bsymbolic --whole-archive --no-undefined -o $PREFIX/libffmpeg.so libavcodec/libavcodec.a libavfilter/libavfilter.a libavresample/libavresample.a libavformat/libavformat.a libavutil/libavutil.a libswscale/libswscale.a -lc -lm -lz -ldl -llog -lx264 --warn-once --dynamic-linker=/system/bin/linker $PREBUILT/lib/gcc/arm-linux-androideabi/4.4.3/libgcc.a
}

build_one


  



  After building library I have been able to build android ndk. A little part of my JNI code is here.

  



  JNIEXPORT jint JNICALL Java_com_example_testjava_TestjniActivity_initencoder(JNIEnv* env,jobject obj){

    av_register_all();
    avcodec_register_all();
    codec = avcodec_find_encoder(AV_CODEC_ID_H264);
    if (!codec) {
      __android_log_write(ANDROID_LOG_INFO, "debug", "not found");                
       return -1;
    }
.
.
.
}


  



  When I run my java source code that calls initencoder() I get -1 as return value and logcat prints "not found". That means avcodec_find_encoder() returns null and if condition is being ok. I don't know what's wrong. Why this function is returning null ? I have searched a lot but did not find any solution that could guide me to right direction. some says to use avcodec_init(). But ndk-build command fails and shows error saying undefined reference to 'avcodec_init()'. I have started with library build because I thought may be I am doing wrong from the first stage. Did I make any mistake in library building like not enabling things that I should ? Please help me here. This is kind of urgent for me.

  


• Minimum FFMPEG configure options for H264 decoding

  26 novembre 2019, par Big Guy

  I’m working on a project using an LS1021A board, which has a Cortex-A7, NEON, FPU, etc, which seems to be very similar to a Raspberry Pi 2. We are streaming in H264 via RTP (UDP) with VLC to simulate an IP Camera with the end goal of extracting the raw RGB frame data (in a C app) to be used elsewhere in the system.

  So, I’d like to compile ffmpeg and the associated libs to do only H264 decoding, using libavcodec in C code. This will be running on a custom linux OS with tight size constraints, so lib size needs to be as small as possible.

  I have the following so far after a day or so of googling :

  ./configure --disable-encoders --disable-decoders --enable-decoder=h264 --enable-small --enable-cross-compile --arch-arm --target-os=linux --cpu=cortex-a7 --disable-debug --cross-prefix=${GCC_PREFIX} --prefix=/c/Users/labuser/Desktop/build --extra-cflags='march=armv7-a -mtune=cortex-a7 -mfpu=neon-vfpv4 -mfloat-abi=hard' --enable-neon --disable-devices --disable-sdl --disable-ffprobe --disable-ffserver --disable-doc --disable-w32threads --disable-ffplay

  Since I’ll be using libavcodec directly, I’m not sure if some of these —disable switches are needed, but can anyone give any pointers on if this looks acceptable or if there are any other switches I should be using ?

  Thanks !