Cross compiling (and troubleshooting) FFMPEG (with raspberry pi toolchain)

This post is just these Two   posts + troubleshooting (cflags from this blog )

Basic instructions (provided you've set up your toolchain and downloaded, untar'd everything)


configure fdk_aac and build

 CCPREFIX="/opt/tools/arm-bcm2708/arm-bcm2708hardfp-linux-gnueabi/bin/arm-bcm2708hardfp-linux-gnueabi-"
CC="arm-bcm2708hardfp-linux-gnueabi-gcc"
CFLAGS="-O3 -march=armv6zk -mfpu=vfp -mfloat-abi=hard"
./configure --host=arm-linux --prefix=/home/david/built_ffmpeg/ --enable-static --disable-shared
make -j$(nproc) && make install


configure x264 and build

./configure --host=arm-linux --enable-static --cross-prefix=${CCPREFIX} --prefix=/home/david/built_ffmpeg/ --extra-cflags='-O3 -march=armv6zk -mfpu=vfp -mfloat-abi=hard' --extra-ldflags='-O3 -march=armv6zk -mfpu=vfp -mfloat-abi=hard'
make -j$(nproc) && make install

configure and build ffmpeg

(Note: I disable everything but libx264 and libfdk_aac because that's all I need)

./configure --enable-cross-compile --cross-prefix=${CCPREFIX} --arch=armel --target-os=linux --prefix=/home/david/built_ffmpeg/ \
            --disable-all \
            --enable-gpl \
            --enable-libx264 \
            --enable-nonfree \
            --enable-libfdk_aac \
            --extra-cflags="-I/home/david/built_ffmpeg/include -O3 -march=armv6zk -mfpu=vfp -mfloat-abi=hard" \
            --extra-ldflags="-L/home/david/built_ffmpeg/lib" \
            --extra-libs=-ldl
make -j$(nproc) && make install

Clearly replacing "/home/david/built_ffmpeg" for your prefix

Note: these cflags don't seem to change cpu load.




Troubleshooting:

If you are getting "No valid C compiler found", but the toolchain is in your path and on your CCPREFIX, then most likely you are missing some libraries to use it (the toolchain uses shared libraries, which you might not have)

Run:

echo "int main(){0;}" | arm-bcm2708hardfp-linux-gnueabi-gcc -x c -

To test your toolchain. It shouldn't work, and will tell you which library you are missing. Install it and try again.


If you are trying to compile ffmpeg with x264 and you've built it with --enable-static you'll likely get the error "libx264 not found" ( just like this ), even though the cflags, ldflags and prefix are all OK.
The problem is that (as you can see in your config.log) you don't have some OpenGL libraries.

The solution is on the next post ( here ) and tells you to add these flags

 --disable-opencl \
 --disable-avs \
 --disable-cli \
 --disable-ffms \
 --disable-gpac \
 --disable-lavf \
 --disable-swscale

If you are trying to build the alsa lib and get "configure: error: C compiler cannot create executables"  you need to set the CC environment variable:

CC="arm-bcm2708hardfp-linux-gnueabi-gcc" ./configure --host=arm-linux --prefix=YOUR_PREFIX

If you get an error saying it can’t find arm-linux-gnueabihf/python2.7/pyconfig.h you can add

 --disable-python

to the configure flags (or get the relevant files from https://packages.debian.org/sid/armhf/libpython2.7-dev/filelist )








This is how I stream to my nginx-rtmp server.



raspivid -n -vs -ih -pf high -t 0 -ISO 800 -ex fixedfps -w 1280 -h 720 -fps $fps -g $((2*fps)) -b $bw -o - \
        | ../ffmpeg \
                -framerate $fps -r $fps -i - \
                -f alsa -ar $ar -ac 1 -itsoffset 10 -i btheadset \
                -c:v copy -r $fps -vsync drop \
                -c:a libfdk_aac -afterburner 0 -async 1 -ar 48000 -ac 1 -b:a 48k \
                -tune zerolatency -bufsize 100k \
                -rtmp_buffer 100 -rtmp_live live \
                -f flv rtmp://$HOST:1935/$STREAM/movie


The CPU load is ~20%.
If I only encode audio, the CPU load is about ~13%.