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libvmaf.a -- A Static Library of VMAF

VMAF is now packaged into a static library called libvmaf.a.

To build libvmaf.a, make the ptools library first, followed by libvmaf:

cd src/ptools; make; cd ../../src/libvmaf; make; cd ../..;

The static library built is at src/libvmaf/libvmaf.a. To install the library, run:

sudo make install

This copies the library header libvmaf.h under usr/local/include, library libvmaf.a under usr/local/lib and all the model files under usr/local/share. You can use the header libvmaf.h in your program. It contains an API which can be called from any C/C++ program:

int compute_vmaf(double* vmaf_score, char* fmt, int width, int height, 
int (*read_frame)(float *ref_data, float *main_data, float *temp_data, int stride, void *user_data), 
void *user_data, char *model_path, char *log_path, char *log_fmt, int disable_clip, 
int disable_avx, int enable_transform, int phone_model, int do_psnr, int do_ssim, 
int do_ms_ssim, char *pool_method, int thread, int subsample, int enable_conf_interval);

Here, read_frame is a callback function which can be used to pass data from a program to VMAF. user_data is a program specific data that can be used by the callback function. For sample usage of compute_vmaf, refer to libvmaf/tools/main.cpp.

To test the library, run:

make testlib

This command will build an executable testlib using this library together with libvmaf/tools/main.cpp.

To uninstall the library run:

make uninstall

Use libvmaf.a with FFmpeg

After installing libvmaf.a, you can use it with FFmpeg. Under FFmpeg directory, configure, build and install FFmpeg with:

./configure --enable-libvmaf --enable-version3
make install

Using FFmpeg with libvmaf is very powerful, as you can create complex filters to calculate VMAF directly on videos of different encoding formats and resolutions. For the best practices of computing VMAF at the right resolution, refer to our techblog. Below is an example on how you can compare a downscaled video with its original 1080p source:

ffmpeg -i main.mpg -i ref.mpg -filter_complex \
"[0:v]scale=1920x1080:flags=bicubic[main];[main][1:v]libvmaf" -f null -

Here main.mpg is a downscaled and encoded video and ref.mpg is its reference source at 1080p. The command scales the first input video (0:v) and forwards it to VMAF (libvmaf) with the label main, where it is compared against the second input reference video, 1:v. Bicubic upsampling is used (also see the techblog for the recommendation on upsampling methods).

See the FFmpeg's guide to libvmaf, the FFmpeg Filtering Guide for more examples of complex filters, and the Scaling Guide for information about scaling and using different scaling algorithms.

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