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• Things I Have Learned About Emscripten

  1er septembre 2015, par Multimedia Mike — Cirrus Retro

  3 years ago, I released my Game Music Appreciation project, a website with a ludicrously uninspired title which allowed users a relatively frictionless method to experience a range of specialized music files related to old video games. However, the site required use of a special Chrome plugin. Ever since that initial release, my #1 most requested feature has been for a pure JavaScript version of the music player.

  “Impossible !” I exclaimed. “There’s no way JS could ever run fast enough to run these CPU emulators and audio synthesizers in real time, and allow for the visualization that I demand !” Well, I’m pleased to report that I have proved me wrong. I recently quietly launched a new site with what I hope is a catchier title, meant to evoke a cloud-based retro-music-as-a-service product : Cirrus Retro. Right now, it’s basically the same as the old site, but without the wonky Chrome-specific technology.

  Along the way, I’ve learned a few things about using Emscripten that I thought might be useful to share with other people who wish to embark on a similar journey. This is geared more towards someone who has a stronger low-level background (such as C/C++) vs. high-level (like JavaScript).

  General Goals
  Do you want to cross-compile an entire desktop application, one that relies on an extensive GUI toolkit ? That might be difficult (though I believe there is a path for porting qt code directly with Emscripten). Your better wager might be to abstract out the core logic and processes of the program and then create a new web UI to access them.

  Do you want to compile a game that basically just paints stuff to a 2D canvas ? You’re in luck ! Emscripten has a porting path for SDL. Make a version of your C/C++ software that targets SDL (generally not a tall order) and then compile that with Emscripten.

  Do you just want to cross-compile some functionality that lives in a library ? That’s what I’ve done with the Cirrus Retro project. For this, plan to compile the library into a JS file that exports some public functions that other, higher-level, native JS (i.e., JS written by a human and not a computer) will invoke.

  Memory Levels
  When porting C/C++ software to JavaScript using Emscripten, you have to think on 2 different levels. Or perhaps you need to force JavaScript into a low level C lens, especially if you want to write native JS code that will interact with Emscripten-compiled code. This often means somehow allocating chunks of memory via JS and passing them to the Emscripten-compiled functions. And you wouldn’t believe the type of gymnastics you need to execute to get native JS and Emscripten-compiled JS to cooperate.
  

  “Emscripten : Pointers and Pointers” is the best (and, really, ONLY) explanation I could find for understanding the basic mechanics of this process, at least when I started this journey. However, there’s a mistake in the explanation that left me confused for a little while, and I’m at a loss to contact the author (doesn’t anyone post a simple email address anymore ?).

  Per the best of my understanding, Emscripten allocates a large JS array and calls that the memory space that the compiled C/C++ code is allowed to operate in. A pointer in C/C++ code will just be an index into that mighty array. Really, that’s not too far off from how a low-level program process is supposed to view memory– as a flat array.

  Eventually, I just learned to cargo-cult my way through the memory allocation process. Here’s the JS code for allocating an Emscripten-compatible byte buffer, taken from my test harness (more on that later) :

  var musicBuffer = fs.readFileSync(testSpec[’filename’]) ;
  var musicBufferBytes = new Uint8Array(musicBuffer) ;
  var bytesMalloc = player._malloc(musicBufferBytes.length) ;
  var bytes = new Uint8Array(player.HEAPU8.buffer, bytesMalloc, musicBufferBytes.length) ;
  bytes.set(new Uint8Array(musicBufferBytes.buffer)) ;
  

  So, read the array of bytes from some input source, create a Uint8Array from the bytes, use the Emscripten _malloc() function to allocate enough bytes from the Emscripten memory array for the input bytes, then create a new array… then copy the bytes…

  You know what ? It’s late and I can’t remember how it works exactly, but it does. It has been a few months since I touched that code (been fighting with front-end website tech since then). You write that memory allocation code enough times and it begins to make sense, and then you hope you don’t have to write it too many more times.

  Multithreading
  You can’t port multithreaded code to JS via Emscripten. JavaScript has no notion of threads ! If you don’t understand the computer science behind this limitation, a more thorough explanation is beyond the scope of this post. But trust me, I’ve thought about it a lot. In fact, the official Emscripten literature states that you should be able to port most any C/C++ code as long as 1) none of the code is proprietary (i.e., all the raw source is available) ; and 2) there are no threads.

  Yes, I read about the experimental pthreads support added to Emscripten recently. Don’t get too excited ; that won’t be ready and widespread for a long time to come as it relies on a new browser API. In the meantime, figure out how to make your multithreaded C/C++ code run in a single thread if you want it to run in a browser.

  Printing Facility
  Eventually, getting software to work boils down to debugging, and the most primitive tool in many a programmer’s toolbox is the humble print statement. A print statement allows you to inspect a piece of a program’s state at key junctures. Eventually, when you try to cross-compile C/C++ code to JS using Emscripten, something is not going to work correctly in the generated JS “object code” and you need to understand what. You’ll be pleading for a method of just inspecting one variable deep in the original C/C++ code.

  I came up with this simple printf-workalike called emprintf() :

  #ifndef EMPRINTF_H
  #define EMPRINTF_H
  #include <stdio .h>
  
  #include <stdarg .h>
  
  #include <emscripten .h>
  #define MAX_MSG_LEN 1000
  /* NOTE : Don’t pass format strings that contain single quote (’) or newline
  
  * characters. */
  
  static void emprintf(const char *format, ...)
  
  
  
      char msg[MAX_MSG_LEN] ;
  
      char consoleMsg[MAX_MSG_LEN + 16] ;
  
      va_list args ;
  
      /* create the string */
  
      va_start(args, format) ;
  
      vsnprintf(msg, MAX_MSG_LEN, format, args) ;
  
      va_end(args) ;
      /* wrap the string in a console.log(’’) statement */
  
      snprintf(consoleMsg, MAX_MSG_LEN + 16, "console.log(’%s’)", msg) ;
      /* send the final string to the JavaScript console */
  
      emscripten_run_script(consoleMsg) ;
  
  
  #endif  /* EMPRINTF_H */
  

  Put it in a file called “emprint.h”. Include it into any C/C++ file where you need debugging visibility, use emprintf() as a replacement for printf() and the output will magically show up on the browser’s JavaScript debug console. Heed the comments and don’t put any single quotes or newlines in strings, and keep it under 1000 characters. I didn’t say it was perfect, but it has helped me a lot in my Emscripten adventures.

  Optimization Levels
  Remember to turn on optimization when compiling. I have empirically found that optimizing for size (-Os) leads to the best performance all around, in addition to having the smallest size. Just be sure to specify some optimization level. If you don’t, the default is -O0 which offers horrible performance when running in JS.

  Static Compression For HTTP Delivery
  JavaScript code compresses pretty efficiently, even after it has been optimized for size using -Os. I routinely see compression ratios between 3.5:1 and 5:1 using gzip.

  Web servers in this day and age are supposed to be smart enough to detect when a requesting web browser can accept gzip-compressed data and do the compression on the fly. They’re even supposed to be smart enough to cache compressed output so the same content is not recompressed for each request. I would have to set up a series of tests to establish whether either of the foregoing assertions are correct and I can’t be bothered. Instead, I took it into my own hands. The trick is to pre-compress the JS files and then instruct the webserver to serve these files with a ‘Content-Type’ of ‘application/javascript’ and a ‘Content-Encoding’ of ‘gzip’.

  1. Compress your large Emscripten-build JS files with ‘gzip’ : ‘gzip compiled-code.js’
  2. Rename them from extension .js.gz to .jsgz
  3. Tell the webserver to deliver .jsgz files with the correct Content-Type and Content-Encoding headers

  To do that last step with Apache, specify these lines :

  AddType application/javascript jsgz
  AddEncoding gzip jsgz
  

  They belong in either a directory’s .htaccess file or in the sitewide configuration (/etc/apache2/mods-available/mime.conf works on my setup).

  Build System and Build Time Optimization
  Oh goodie, build systems ! I had a very specific manner in which I wanted to build my JS modules using Emscripten. Can I possibly coerce any of the many popular build systems to do this ? It has been a few months since I worked on this problem specifically but I seem to recall that the build systems I tried to used would freak out at the prospect of compiling stuff to a final binary target of .js.

  I had high hopes for Bazel, which Google released while I was developing Cirrus Retro. Surely, this is software that has been battle-tested in the harshest conditions of one of the most prominent software-developing companies in the world, needing to take into account the most bizarre corner cases and still build efficiently and correctly every time. And I have little doubt that it fulfills the order. Similarly, I’m confident that Google also has a team of no fewer than 100 or so people dedicated to developing and supporting the project within the organization. When you only have, at best, 1-2 hours per night to work on projects like this, you prefer not to fight with such cutting edge technology and after losing 2 or 3 nights trying to make a go of Bazel, I eventually put it aside.

  I also tried to use Autotools. It failed horribly for me, mostly for my own carelessness and lack of early-project source control.

  After that, it was strictly vanilla makefiles with no real dependency management. But you know what helps in these cases ? ccache ! Or at least, it would if it didn’t fail with Emscripten.

  Quick tip : ccache has trouble with LLVM unless you set the CCACHE_CPP2 environment variable (e.g. : “export CCACHE_CPP2=1”). I don’t remember the specifics, but it magically fixes things. Then, the lazy build process becomes “make clean && make”.

  Testing
  If you have never used Node.js, testing Emscripten-compiled JS code might be a good opportunity to start. I was able to use Node.js to great effect for testing the individually-compiled music player modules, wiring up a series of invocations using Python for a broader test suite (wouldn’t want to go too deep down the JS rabbit hole, after all).

  Be advised that Node.js doesn’t enjoy the same kind of JIT optimizations that the browser engines leverage. Thus, in the case of time critical code like, say, an audio synthesis library, the code might not run in real time. But as long as it produces the correct bitwise waveform, that’s good enough for continuous integration.

  Also, if you have largely been a low-level programmer for your whole career and are generally unfamiliar with the world of single-threaded, event-driven, callback-oriented programming, you might be in for a bit of a shock. When I wanted to learn how to read the contents of a file in Node.js, this is the first tutorial I found on the matter. I thought the code presented was a parody of bad coding style :

  var fs = require("fs") ;
  var fileName = "foo.txt" ;
  fs.exists(fileName, function(exists) 
  
    if (exists) 
  
      fs.stat(fileName, function(error, stats) 
  
        fs.open(fileName, "r", function(error, fd) 
  
          var buffer = new Buffer(stats.size) ;
  
          fs.read(fd, buffer, 0, buffer.length, null, function(error, bytesRead, buffer) 
  
            var data = buffer.toString("utf8", 0, buffer.length) ;
  
            console.log(data) ;
  
            fs.close(fd) ;
  
          ) ;
  
        ) ;
  
      ) ;
  
    ) ;
  

  Apparently, this kind of thing doesn’t raise an eyebrow in the JS world.

  Now, I understand and respect the JS programming model. But this was seriously frustrating when I first encountered it because a simple script like the one I was trying to write just has an ordered list of tasks to complete. When it asks for bytes from a file, it really has nothing better to do than to wait for the answer.

  Thankfully, it turns out that Node’s fs module includes synchronous versions of the various file access functions. So it’s all good.

  Conclusion
  I’m sure I missed or underexplained some things. But if other brave souls are interested in dipping their toes in the waters of Emscripten, I hope these tips will come in handy.

  The post Things I Have Learned About Emscripten first appeared on Breaking Eggs And Making Omelettes.

• Subtitling Sierra RBT Files

  2 juin 2016, par Multimedia Mike — Game Hacking

  This is part 2 of the adventure started in my Subtitling Sierra VMD Files post. After I completed the VMD subtitling, The Translator discovered a wealth of animation files in a format called RBT (this apparently stands for “Robot” but I think “Ribbit” format could be more fun). What are we going to do ? We had come so far by solving the VMD subtitling problem for Phantasmagoria. It would be a shame if the effort ground to a halt due to this.

  Fortunately, the folks behind the ScummVM project already figured out enough of the format to be able to decode the RBT files in Phantasmagoria.

  In the end, I was successful in creating a completely standalone tool that can take a Robot file and a subtitle file and create a new Robot file with subtitles. The source code is here (subtitle-rbt.c). Here’s what the final result looks like :

  
  
  “What’s in the refrigerator ?” I should note at this juncture that I am not sure if this particular Robot file even has sound or dialogue since I was conducting these experiments on a computer with non-working audio.
  

  The RBT Format
  I have created a new MultimediaWiki page describing the Robot Animation format based on the ScummVM source code. I have not worked with a format quite like this before. These are paletted animations which consist of a sequence of independent frames that are designed to be overlaid on top of static background. Because of these characteristics, each frame encodes its own unique dimensions and origin coordinate within the frame. While the Phantasmagoria VMD files are usually 288×144 (which are usually double-sized for the benefit of a 640×400 Super VGA canvas), these frames are meant to be plotted on a game field that was roughly 576×288 (288×144 doublesized).
  

  For example, 2 minimalist animation frames from a desk investigation Robot file :

  
  
  100×147

  
  101×149
  

  As for compression, my first impression was that the algorithm was the same as VMD. This is wrong. It evidently uses an unmodified version of a standard algorithm called Lempel-Ziv-Stac (LZS). It shows up in several RFCs and was apparently used in MS-DOS’s transparent disk compression scheme.

  Approach
  Thankfully, many of the lessons I learned from the previous project are applicable to this project, including : subtitle library interfacing, subtitling in the paletted colorspace, and replacing encoded frames from the original file instead of trying to create a new file.

  Here is the pitch for this project :

  • Create a C program that can traverse through an input file, piece by piece, and generate an output file. The result of this should be a bitwise identical file.
  • Adapt the LZS compression decoding algorithm from ScummVM into the new tool. Make the tool dump raw Portable NetMap (PNM) files of varying dimensions and ensure that they look correct.
  • Compress using LZS.
  • Stretch the frames and draw subtitles.
  • More compression. Find the minimum window for each frame.

  Compression
  Normally, my first goal is to decompress the video and store the data in a raw form. However, this turned out to be mathematically intractable. While the format does support both compressed and uncompressed frames (even though ScummVM indicates that the uncompressed path is yet unexercised), the goal of this project requires making the frames so large that they overflow certain parameters of the file.

  A Robot file has a sequence of frames and 2 tables describing the size of each frame. One table describes the entire frame size (audio + video) while the second table describes just the video frame size. Since these tables only use 16 bits to specify a size, the maximum frame size is 65536 bytes. Leaving space for the audio portion of the frame, this only leaves a per-frame byte budget of about 63000 bytes for the video. Expanding the frame to 576×288 (165,888 pixels) would overflow this limit.

  Anyway, the upshot is that I needed to compress the data up front.

  Fortunately, the LZS compressor is pretty straightforward, at least if you have experience writing VLC-oriented codecs. While the algorithm revolves around back references, my approach was to essentially write an RLE encoder. My compressor would search for runs of data (plentiful when I started to stretch the frame for subtitling purposes). When a run length of n=3 or more of the same pixel is found, encode the pixel by itself, and then store a back reference of offset -1 and length (n-1). It took a little while to iron out a few problems, but I eventually got it to work perfectly.

  I have to say, however, that the format is a little bit weird in how it codes very large numbers. The length encoding is somewhat Golomb-like, i.e., smaller values are encoded with fewer bits. However, when it gets to large numbers, it starts encoding counts of 15 as blocks of 1111. For example, 24 is bigger than 7. Thus, emit 1111 into the bitstream and subtract 8 from 23 -> 16. Still bigger than 15, so stuff another 1111 into the bitstream and subtract 15. Now we’re at 1, so stuff 0001. So 24 is 11111111 0001. 12 bits is not too horrible. But the total number of bytes (value / 30). So a value of 300 takes around 10 bytes (80 bits) to encode.

  Palette Slices
  As in the VMD subtitling project, I took the subtitle color offered in the subtitle spec file as a suggestion and used Euclidean distance to match to the closest available color in the palette. One problem, however, is that the palette is a lot smaller in these animations. According to my notes, for the set of animations I scanned, only about 80 colors were specified, starting at palette index 55. I hypothesize that different slices of the palette are reserved for different uses. E.g., animation, background, and user interface. Thus, there is a smaller number of colors to draw upon for subtitling purposes.

  Scaling
  One bit of residual weirdness in this format is the presence of a per-frame scale factor. While most frames set this to 100 (100% scale), I have observed 70%, 80%, and 90%. ScummVM is a bit unsure about how to handle these, so I am as well. However, I eventually realized I didn’t really need to care, at least not when decoding and re-encoding the frame. Just preserve the scale factor. I intend to modify the tool further to take scale factor into account when creating the subtitle.

  The Final Resolution
  Right around the time that I was composing this post, The Translator emailed me and notified me that he had found a better way to subtitle the Robot files by modifying the scripts, rendering my entire approach moot. The result is much cleaner :

  
  
  Turns out that the engine supported subtitles all along
  

  It’s a good thing that I enjoyed the challenge or I might be annoyed at this point.

  See Also

  • Subtitling Sierra VMD Files : My effort to subtitle the main FMV files found in Sierra games.

  The post Subtitling Sierra RBT Files first appeared on Breaking Eggs And Making Omelettes.

• undefined reference to ffmpeg functions in native code using Android Studio 2.2

  12 octobre 2016, par Krzysztof Kansy

  I have a problem with using ffmpeg in Android Studio 2.2 using NDK 13 and new Cmake building system. FFmpeg version is 3.1.4.
  The system I’m working on is Linux Mint 18 64-bit.
  At the build time I’m getting undefined reference error each time I use ffpeg functions.

  My MainActivity.java :

  public class MainActivity extends AppCompatActivity {
  
  
  
      @Override
  
      protected void onCreate(Bundle savedInstanceState) {
  
          super.onCreate(savedInstanceState);
  
          setContentView(R.layout.activity_main);
  
  
  
      // Example of a call to a native method
  
      TextView tv = (TextView) findViewById(R.id.sample_text);
  
      tv.setText(stringFromJNI());
  
      }
  
  
  
      /**
  
       * A native method that is implemented by the 'native-lib' native library,
  
       * which is packaged with this application.
  
       */
  
      public native String stringFromJNI();
  
  
  
      // Used to load the 'native-lib' library on application startup.
  
      static {
  
          System.loadLibrary("native-lib");
  
      }
  
  }

  My native class (undefined reference is pointing to av_init_packet(&avPacket)) :

  #include 
  
  #include <string>
  
  #include <android></android>log.h>
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  
  
  
  
  extern "C"
  
  jstring
  
  Java_com_example_tito_jnitest_MainActivity_stringFromJNI(
  
          JNIEnv* env,
  
          jobject /* this */) {
  
  
  
      std::string hello = "Hello from C++";
  
  
  
      __android_log_print(ANDROID_LOG_INFO, "JNItest", "Hello from JNI!");
  
  
  
      AVPacket avPacket;
  
      av_init_packet(&amp;avPacket);
  
  
  
      return env->NewStringUTF(hello.c_str());
  
  }
  
  </string>

  build.gradle script

  apply plugin: 'com.android.application'
  
  
  
  android {
  
      compileSdkVersion 24
  
      buildToolsVersion "24.0.3"
  
      defaultConfig {
  
          applicationId "com.example.tito.jnitest"
  
          minSdkVersion 19
  
          targetSdkVersion 24
  
          versionCode 1
  
          versionName "1.0"
  
          testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
  
          externalNativeBuild {
  
              cmake {
  
                  // Passes optional arguments to CMake.
  
                  cppFlags "-frtti -fexceptions"
  
                  abiFilters 'armeabi'
  
              }
  
          }
  
      }
  
  
  
      sourceSets {
  
          main {
  
              jniLibs.srcDirs = ['/home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs']
  
          }
  
      }
  
  
  
      buildTypes {
  
          release {
  
              minifyEnabled false
  
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
  
          }
  
      }
  
      externalNativeBuild {
  
          cmake {
  
              path "CMakeLists.txt"
  
          }
  
      }
  
  }
  
  
  
  dependencies {
  
      compile fileTree(dir: 'libs', include: ['*.jar'])
  
      androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
  
          exclude group: 'com.android.support', module: 'support-annotations'
  
      })
  
      compile 'com.android.support:appcompat-v7:24.2.1'
  
      testCompile 'junit:junit:4.12'
  
  }

  CMakeLists.txt

  cmake_minimum_required(VERSION 3.4.1)
  
  
  
  include_directories(/home/tito/Android/Sdk/ndk-bundle/sources/ffmpeg-3.1.4/android/${ANDROID_ABI}/include)
  
  
  
  #set(CMAKE_VERBOSE_MAKEFILE on)
  
  #set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
  
  
  
  add_library( avutil
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  avutil
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libavutil-55.so )
  
  
  
  add_library( swscale
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  swscale
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libswscale-4.so )
  
  
  
  add_library( swresample
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  swresample
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libswresample-2.so )
  
  
  
  add_library( avcodec
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  avcodec
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libavcodec-57.so )
  
  
  
  add_library( avfilter
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  avfilter
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libavfilter-6.so )
  
  
  
  add_library( avformat
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  avformat
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libavformat-57.so )
  
  
  
  add_library( avdevice
  
               SHARED
  
               IMPORTED )
  
  
  
  set_target_properties(
  
                  avdevice
  
                  PROPERTIES IMPORTED_LOCATION
  
                  /home/tito/AndroidStudioProjects/JNItest/app/src/main/jniLibs/${ANDROID_ABI}/libavdevice-57.so )
  
  
  
  add_library( native-lib
  
               SHARED
  
               src/main/cpp/native-lib.cpp )
  
  
  
  find_library( log-lib
  
                log )
  
  
  
  target_link_libraries(native-lib ${log-lib} avutil swscale swresample avcodec avfilter avformat avdevice)

  Build process of ffmpeg seemed to be successful. Here’s my build script :

  #!/bin/bash
  
  NDK=/home/tito/Android/Sdk/ndk-bundle
  
  SYSROOT=$NDK/platforms/android-19/arch-arm/
  
  TOOLCHAIN=$NDK/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64
  
  function build_one
  
  {
  
  ./configure \
  
  --prefix=$PREFIX \
  
  --disable-static \
  
  --enable-shared \
  
  --disable-doc \
  
  --disable-ffmpeg \
  
  --disable-ffplay \
  
  --disable-ffprobe \
  
  --disable-ffserver \
  
  --disable-doc \
  
  --cross-prefix=$TOOLCHAIN/bin/arm-linux-androideabi- \
  
  --target-os=linux \
  
  --arch=arm \
  
  --enable-cross-compile \
  
  --sysroot=$SYSROOT \
  
  --extra-cflags="-Os -fpic -marm" \
  
  --extra-ldflags="-marm" \
  
  $ADDITIONAL_CONFIGURE_FLAG
  
  make clean
  
  make
  
  make install
  
  }
  
  CPU=armeabi
  
  PREFIX=$(pwd)/android/$CPU
  
  build_one

  One thing I noticed that could indicate that something is wrong with ffmpeg build is warning WARNING: /home/tito/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-pkg-config not found, library detection may fail. during building. I’m not sure if this may be cause of problems.
  

  I was trying to build for all of the ABIs, but for now I decided to focus on making just armeabi working. I’m having exact same failure after using e.g. arm64-v8a.

  Finally, here is the gradle console’s content with error :

  Executing tasks: [:app:assembleDebug]
  
  
  
  Configuration on demand is an incubating feature.
  
  Incremental java compilation is an incubating feature.
  
  :app:preBuild UP-TO-DATE
  
  :app:preDebugBuild UP-TO-DATE
  
  :app:checkDebugManifest
  
  :app:preReleaseBuild UP-TO-DATE
  
  :app:prepareComAndroidSupportAnimatedVectorDrawable2421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportAppcompatV72421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportCompat2421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportCoreUi2421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportCoreUtils2421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportFragment2421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportMediaCompat2421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportV42421Library UP-TO-DATE
  
  :app:prepareComAndroidSupportSupportVectorDrawable2421Library UP-TO-DATE
  
  :app:prepareDebugDependencies
  
  :app:compileDebugAidl UP-TO-DATE
  
  :app:compileDebugRenderscript UP-TO-DATE
  
  :app:generateDebugBuildConfig UP-TO-DATE
  
  :app:generateDebugResValues UP-TO-DATE
  
  :app:generateDebugResources UP-TO-DATE
  
  :app:mergeDebugResources UP-TO-DATE
  
  :app:processDebugManifest UP-TO-DATE
  
  :app:processDebugResources
  
  :app:generateDebugSources
  
  :app:incrementalDebugJavaCompilationSafeguard UP-TO-DATE
  
  :app:compileDebugJavaWithJavac UP-TO-DATE
  
  :app:generateJsonModelDebug UP-TO-DATE
  
  :app:externalNativeBuildDebug
  
    building /home/tito/AndroidStudioProjects/JNItest/app/build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so
  
  :app:externalNativeBuildDebug FAILED
  
  
  
  FAILURE: Build failed with an exception.
  
  
  
  * What went wrong:
  
  Execution failed for task ':app:externalNativeBuildDebug'.
  
  > Build command failed.
  
    Error while executing '/home/tito/Android/Sdk/cmake/3.6.3155560/bin/cmake' with arguments {--build /home/tito/AndroidStudioProjects/JNItest/app/.externalNativeBuild/cmake/debug/armeabi --target native-lib}
  
    [1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o
  
    [2/2] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so
  
    FAILED: : && /home/tito/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++  -target armv5te-none-linux-androideabi -gcc-toolchain /home/tito/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64 --sysroot=/home/tito/Android/Sdk/ndk-bundle/platforms/android-19/arch-arm -fPIC -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -frtti -fexceptions -O0 -fno-limit-debug-info -O0 -fno-limit-debug-info  -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ../../../../build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o  /home/tito/Android/Sdk/ndk-bundle/platforms/android-19/arch-arm/usr/lib/liblog.so ../../../../src/main/jniLibs/armeabi/libavutil-55.so ../../../../src/main/jniLibs/armeabi/libswscale-4.so ../../../../src/main/jniLibs/armeabi/libswresample-2.so ../../../../src/main/jniLibs/armeabi/libavcodec-57.so ../../../../src/main/jniLibs/armeabi/libavfilter-6.so ../../../../src/main/jniLibs/armeabi/libavformat-57.so ../../../../src/main/jniLibs/armeabi/libavdevice-57.so -lm "/home/tito/Android/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi/libgnustl_static.a" "-latomic" && :
  
    /home/tito/AndroidStudioProjects/JNItest/app/src/main/cpp/native-lib.cpp:18: error: undefined reference to 'av_init_packet(AVPacket*)'
  
    clang++: error: linker command failed with exit code 1 (use -v to see invocation)
  
    ninja: build stopped: subcommand failed.
  
  
  
  
  
  * Try:
  
  Run with --info or --debug option to get more log output.
  
  
  
  * Exception is:
  
  org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:externalNativeBuildDebug'.
  
      at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:69)
  
      at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
  
      at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
  
      at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:66)
  
      at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
  
      at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:52)
  
      at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
  
      at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
  
      at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
  
      at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:203)
  
      at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter$EventFiringTaskWorker.execute(DefaultTaskGraphExecuter.java:185)
  
      at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:66)
  
      at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:50)
  
      at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:25)
  
      at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:110)
  
      at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:37)
  
      at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
  
      at org.gradle.execution.DefaultBuildExecuter.access$000(DefaultBuildExecuter.java:23)
  
      at org.gradle.execution.DefaultBuildExecuter$1.proceed(DefaultBuildExecuter.java:43)
  
      at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
  
      at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:37)
  
      at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:30)
  
      at org.gradle.initialization.DefaultGradleLauncher$4.run(DefaultGradleLauncher.java:153)
  
      at org.gradle.internal.Factories$1.create(Factories.java:22)
  
      at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
  
      at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:53)
  
      at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:150)
  
      at org.gradle.initialization.DefaultGradleLauncher.access$200(DefaultGradleLauncher.java:32)
  
      at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:98)
  
      at org.gradle.initialization.DefaultGradleLauncher$1.create(DefaultGradleLauncher.java:92)
  
      at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:91)
  
      at org.gradle.internal.progress.DefaultBuildOperationExecutor.run(DefaultBuildOperationExecutor.java:63)
  
      at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:92)
  
      at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:83)
  
      at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:99)
  
      at org.gradle.tooling.internal.provider.runner.BuildModelActionRunner.run(BuildModelActionRunner.java:46)
  
      at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
  
      at org.gradle.tooling.internal.provider.runner.SubscribableBuildActionRunner.run(SubscribableBuildActionRunner.java:58)
  
      at org.gradle.launcher.exec.ChainingBuildActionRunner.run(ChainingBuildActionRunner.java:35)
  
      at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:48)
  
      at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:30)
  
      at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:81)
  
      at org.gradle.launcher.exec.ContinuousBuildActionExecuter.execute(ContinuousBuildActionExecuter.java:46)
  
      at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:52)
  
      at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:37)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:26)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.RequestStopIfSingleUsedDaemon.execute(RequestStopIfSingleUsedDaemon.java:34)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:74)
  
      at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:72)
  
      at org.gradle.util.Swapper.swap(Swapper.java:38)
  
      at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:72)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.health.DaemonHealthTracker.execute(DaemonHealthTracker.java:47)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:60)
  
      at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:72)
  
      at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:36)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.health.HintGCAfterBuild.execute(HintGCAfterBuild.java:41)
  
      at org.gradle.launcher.daemon.server.api.DaemonCommandExecution.proceed(DaemonCommandExecution.java:120)
  
      at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:50)
  
      at org.gradle.launcher.daemon.server.DaemonStateCoordinator$1.run(DaemonStateCoordinator.java:237)
  
      at org.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
  
      at org.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
  
  Caused by: org.gradle.internal.UncheckedException: Build command failed.
  
  Error while executing '/home/tito/Android/Sdk/cmake/3.6.3155560/bin/cmake' with arguments {--build /home/tito/AndroidStudioProjects/JNItest/app/.externalNativeBuild/cmake/debug/armeabi --target native-lib}
  
  [1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o
  
  [2/2] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so
  
  FAILED: : && /home/tito/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++  -target armv5te-none-linux-androideabi -gcc-toolchain /home/tito/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64 --sysroot=/home/tito/Android/Sdk/ndk-bundle/platforms/android-19/arch-arm -fPIC -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -frtti -fexceptions -O0 -fno-limit-debug-info -O0 -fno-limit-debug-info  -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ../../../../build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o  /home/tito/Android/Sdk/ndk-bundle/platforms/android-19/arch-arm/usr/lib/liblog.so ../../../../src/main/jniLibs/armeabi/libavutil-55.so ../../../../src/main/jniLibs/armeabi/libswscale-4.so ../../../../src/main/jniLibs/armeabi/libswresample-2.so ../../../../src/main/jniLibs/armeabi/libavcodec-57.so ../../../../src/main/jniLibs/armeabi/libavfilter-6.so ../../../../src/main/jniLibs/armeabi/libavformat-57.so ../../../../src/main/jniLibs/armeabi/libavdevice-57.so -lm "/home/tito/Android/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi/libgnustl_static.a" "-latomic" && :
  
  /home/tito/AndroidStudioProjects/JNItest/app/src/main/cpp/native-lib.cpp:18: error: undefined reference to 'av_init_packet(AVPacket*)'
  
  clang++: error: linker command failed with exit code 1 (use -v to see invocation)
  
  ninja: build stopped: subcommand failed.
  
  
  
      at org.gradle.internal.UncheckedException.throwAsUncheckedException(UncheckedException.java:45)
  
      at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:78)
  
      at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.doExecute(AnnotationProcessingTaskFactory.java:228)
  
      at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:221)
  
      at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:210)
  
      at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:621)
  
      at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:604)
  
      at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
  
      at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
  
      ... 70 more
  
  Caused by: Build command failed.
  
  Error while executing '/home/tito/Android/Sdk/cmake/3.6.3155560/bin/cmake' with arguments {--build /home/tito/AndroidStudioProjects/JNItest/app/.externalNativeBuild/cmake/debug/armeabi --target native-lib}
  
  [1/2] Building CXX object CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o
  
  [2/2] Linking CXX shared library ../../../../build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so
  
  FAILED: : && /home/tito/Android/Sdk/ndk-bundle/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++  -target armv5te-none-linux-androideabi -gcc-toolchain /home/tito/Android/Sdk/ndk-bundle/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64 --sysroot=/home/tito/Android/Sdk/ndk-bundle/platforms/android-19/arch-arm -fPIC -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -g -DANDROID -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -march=armv5te -mtune=xscale -msoft-float -fno-integrated-as -mthumb -Wa,--noexecstack -Wformat -Werror=format-security -fno-exceptions -fno-rtti -frtti -fexceptions -O0 -fno-limit-debug-info -O0 -fno-limit-debug-info  -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -Wl,--build-id -Wl,--warn-shared-textrel -Wl,--fatal-warnings -Wl,--no-undefined -Wl,-z,noexecstack -Qunused-arguments -Wl,-z,relro -Wl,-z,now -shared -Wl,-soname,libnative-lib.so -o ../../../../build/intermediates/cmake/debug/obj/armeabi/libnative-lib.so CMakeFiles/native-lib.dir/src/main/cpp/native-lib.cpp.o  /home/tito/Android/Sdk/ndk-bundle/platforms/android-19/arch-arm/usr/lib/liblog.so ../../../../src/main/jniLibs/armeabi/libavutil-55.so ../../../../src/main/jniLibs/armeabi/libswscale-4.so ../../../../src/main/jniLibs/armeabi/libswresample-2.so ../../../../src/main/jniLibs/armeabi/libavcodec-57.so ../../../../src/main/jniLibs/armeabi/libavfilter-6.so ../../../../src/main/jniLibs/armeabi/libavformat-57.so ../../../../src/main/jniLibs/armeabi/libavdevice-57.so -lm "/home/tito/Android/Sdk/ndk-bundle/sources/cxx-stl/gnu-libstdc++/4.9/libs/armeabi/libgnustl_static.a" "-latomic" && :
  
  /home/tito/AndroidStudioProjects/JNItest/app/src/main/cpp/native-lib.cpp:18: error: undefined reference to 'av_init_packet(AVPacket*)'
  
  clang++: error: linker command failed with exit code 1 (use -v to see invocation)
  
  ninja: build stopped: subcommand failed.
  
  
  
      at com.android.build.gradle.tasks.ExternalNativeBuildTaskUtils.executeBuildProcessAndLogError(ExternalNativeBuildTaskUtils.java:233)
  
      at com.android.build.gradle.tasks.ExternalNativeBuildTask.executeProcessBatch(ExternalNativeBuildTask.java:231)
  
      at com.android.build.gradle.tasks.ExternalNativeBuildTask.build(ExternalNativeBuildTask.java:163)
  
      at org.gradle.internal.reflect.JavaMethod.invoke(JavaMethod.java:75)
  
      ... 77 more
  
  
  
  
  
  BUILD FAILED
  
  
  
  Total time: 0.723 secs

  Can anyone tell me what I’m doing wrong here ?