Home

Awesome

FFmpeg (libavcodec) Bindings for Clojure

Clojars Project

This system uses the ffi architecture of dtype-next in order to build bindings to JNA, JDK-16 and Graal Native.

Usage

You must have libavcodec installed to use this library; it was already on my machine.

libavcodec58 - FFmpeg library with de/encoders for audio/video codecs - runtime files

   {cnuernber/avclj {:git/url "https://github.com/cnuernber/avclj"
                     :sha "HEAD"}}

Development

Graal Native

I used the dtype-next activate-graal script to activate graal native:

(base) chrisn@chrisn-lt3:~/dev/cnuernber/dtype-next$ source scripts/activate-graal
(base) chrisn@chrisn-lt3:~/dev/cnuernber/dtype-next$ java --version
openjdk 11.0.12 2021-07-20
OpenJDK Runtime Environment GraalVM CE 21.2.0 (build 11.0.12+6-jvmci-21.2-b08)
OpenJDK 64-Bit Server VM GraalVM CE 21.2.0 (build 11.0.12+6-jvmci-21.2-b08, mixed mode, sharing)

Then run the code to generate the graalvm-specific bindings:

clj -M -e "(require 'avclj.gen-bindings)"

Next you will need these system library packages:

Then, after checking under generated_classes to be sure the class generation mechanism worked, simply run scripts/compile.

Graal Native Shared Library

This is using an experimental dtype-next API to export a set of functions from the uberjar to C.

  1. Same setup as above -- gen_bindings generates the bindings for the shared library.
  2. Then run scripts/compile-shared to get a shared library written to the 'library' directory.
  3. Then in the 'library' directory, there is a script to compile a c++ executable against the shared library. It encodes 300 frames or so - then decodes those frames.

One key lesson learned here is that your library export must only reference state that is also referenced from the main class of the uberjar and the exported defn's cannot have typehints.

You have to export LD_LIBRARY_PATH to the library directory in order to load the shared library. But then, hopefully, you will get the right output:

(base) chrisn@chrisn-lt3:~/dev/cnuernber/avclj/library$ export LD_LIBRARY_PATH=$(pwd)
(base) chrisn@chrisn-lt3:~/dev/cnuernber/avclj/library$ ./compile.sh
(base) chrisn@chrisn-lt3:~/dev/cnuernber/avclj/library$ ./a.out
initialized? 0
initialized? 1
[libx264 @ 0x55f64aeb92c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x55f64aeb92c0] profile High, level 2.1, 4:2:0, 8-bit
got encoder: 521232628
[libx264 @ 0x55f64aeb92c0] frame I:2     Avg QP:13.06  size:  1014
[libx264 @ 0x55f64aeb92c0] frame P:103   Avg QP:25.78  size:    88
[libx264 @ 0x55f64aeb92c0] frame B:195   Avg QP:23.22  size:    87
[libx264 @ 0x55f64aeb92c0] consecutive B-frames:  1.3% 36.0%  0.0% 62.7%
[libx264 @ 0x55f64aeb92c0] mb I  I16..4: 50.2% 25.0% 24.8%
[libx264 @ 0x55f64aeb92c0] mb P  I16..4:  1.2%  1.0%  1.0%  P16..4: 12.8%  0.3%  0.0%  0.0%  0.0%    skip:83.8%
[libx264 @ 0x55f64aeb92c0] mb B  I16..4:  0.3%  0.0%  0.0%  B16..8: 32.9%  1.6%  0.0%  direct: 0.0%  skip:65.2%  L0:39.1% L1:60.9% BI: 0.0%
[libx264 @ 0x55f64aeb92c0] 8x8 transform intra:26.4% inter:47.5%
[libx264 @ 0x55f64aeb92c0] coded y,uvDC,uvAC intra: 6.7% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x55f64aeb92c0] i16 v,h,dc,p: 51% 35% 13%  0%
[libx264 @ 0x55f64aeb92c0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 33%  7% 60%  0%  0%  0%  0%  0%  0%
[libx264 @ 0x55f64aeb92c0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 39% 15% 45%  0%  0%  0%  0%  1%  0%
[libx264 @ 0x55f64aeb92c0] i8c dc,h,v,p: 100%  0%  0%  0%
[libx264 @ 0x55f64aeb92c0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x55f64aeb92c0] ref P L0: 89.4%  0.9%  9.7%  0.0%
[libx264 @ 0x55f64aeb92c0] ref B L0: 81.5% 18.1%  0.4%
[libx264 @ 0x55f64aeb92c0] ref B L1: 99.2%  0.8%
[libx264 @ 0x55f64aeb92c0] kb/s:44.84
Encoded 300 frames.  Testing decode to RGB24
Decoding frames 100x100
Jul 31, 2021 8:52:33 AM clojure.tools.logging$eval1$fn__4 invoke
INFO: Reference thread starting
Decoded 300 frames

Extra Information

License - GPLv2

FFmpeg provides a function to get the license of the library; it returns GPLv2 on my system. This library is thus transitively licensed under GPLv2.