4. Android工程中使用FFmpeg的so库 -- JNI头文件定义方法的实现

白话：

闲话不多说，紧接3文中，继续介绍。

4.1 JNI头文件定义方法的实现

1. 将3文中生成com_rk_myapp_MainActivity.h文件拷贝到Android工程的jni目录下，在jni目录下创建com_rk_myapp_MainActivity.c文件，实现相关接口，具体实现细节可以参考代码中的注释：

#include <jni.h>#include <libavcodec/avcodec.h>#include <libavformat/avformat.h>#include <libswscale/swscale.h>#include <libavutil/imgutils.h>#include <libavutil/log.h>#include <android/log.h>#include <android/bitmap.h>#define LOG_TAG "FFMpeg_JNI"#define LOGI(...) __android_log_print(4, LOG_TAG, __VA_ARGS__);AVFormatContext *pFormatCtx;int i, videoStream;AVCodecContext *pCodecCtxOrig;AVCodecContext *pCodecCtx;AVCodec *pCodec;AVFrame *pFrame;AVFrame *pFrameRGB;int numBytes;uint8_t *buffer;AVPacket packet;int frameFinished;struct SwsContext *sws_ctx;char *uri;jobject bitmapObj;void dump_metadata_for_andriod(void *ctx, AVDictionary *m, const char *indent){  if (m && !(av_dict_count(m) == 1 && av_dict_get(m, "language", NULL, 0))) {  AVDictionaryEntry *tag = NULL;  LOGI("%sMetadata:\n", indent);  while ((tag = av_dict_get(m, "", tag, AV_DICT_IGNORE_SUFFIX)))  if (strcmp("language", tag->key)) {  const char *p = tag->value;  LOGI("%s %-16s: ", indent, tag->key);  while (*p) {  char tmp[256];  size_t len = strcspn(p, "\x8\xa\xb\xc\xd");  av_strlcpy(tmp, p, FFMIN(sizeof(tmp), len+1));  av_log(ctx, AV_LOG_INFO, "%s", tmp);  p += len;  if (*p == 0xd) av_log(ctx, AV_LOG_INFO, " ");  if (*p == 0xa) av_log(ctx, AV_LOG_INFO, "\n%s %-16s: ", indent, "");  if (*p) p++;  }  LOGI("\n");  }  }}void av_dump_format_for_android(AVFormatContext *ic, int index,  const char *url, int is_output){  int i;  uint8_t *printed = ic->nb_streams ? av_mallocz(ic->nb_streams) : NULL;  if (ic->nb_streams && !printed)  return;  LOGI("%s #%d, %s, %s '%s':\n",  is_output ? "Output" : "Input",  index,  is_output ? ic->oformat->name : ic->iformat->name,  is_output ? "to" : "from", url);  dump_metadata_for_andriod(NULL, ic->metadata, " ");  if (!is_output) {  LOGI(" Duration: ");  if (ic->duration != AV_NOPTS_VALUE) {  int hours, mins, secs, us;  int64_t duration = ic->duration + (ic->duration <= INT64_MAX - 5000 ? 5000 : 0);  secs = duration / AV_TIME_BASE;  us = duration % AV_TIME_BASE;  mins = secs / 60;  secs %= 60;  hours = mins / 60;  mins %= 60;  LOGI("%02d:%02d:%02d.%02d", hours, mins, secs,  (100 * us) / AV_TIME_BASE);  } else {  LOGI("N/A");  }  if (ic->start_time != AV_NOPTS_VALUE) {  int secs, us;  LOGI(", start: ");  secs = llabs(ic->start_time / AV_TIME_BASE);  us = llabs(ic->start_time % AV_TIME_BASE);  LOGI("%s%d.%06d",  ic->start_time >= 0 ? "" : "-",  secs,  (int) av_rescale(us, 1000000, AV_TIME_BASE));  }  LOGI(", bitrate: ");  if (ic->bit_rate) {  LOGI("%"PRId64" kb/s", (int64_t)ic->bit_rate / 1000);  } else {  LOGI("N/A");  }  LOGI("\n");  }}/* * Class: com_rk_myapp_MainActivity * Method: nativeInit * Signature: ()V */JNIEXPORT void JNICALL Java_com_rk_myapp_MainActivity_nativeInit(JNIEnv *env, jobject obj){  pFormatCtx = NULL;  i = 0;  videoStream = -1;  pCodecCtxOrig = NULL;  pCodecCtx = NULL;  pCodec = NULL;  pFrame = NULL;  pFrameRGB = NULL;  numBytes = 0;  buffer = NULL;  frameFinished = 0;  sws_ctx = NULL;  uri = NULL;  //bitmapObj = NULL;  LOGI("nativeInit()");  av_register_all();}/* * Class: com_rk_myapp_MainActivity * Method: nativeSetUri * Signature: (Ljava/lang/String;)V */JNIEXPORT void JNICALL Java_com_rk_myapp_MainActivity_nativeSetUri(JNIEnv *env, jobject obj, jstring filePath){  uri = (*env)->GetStringUTFChars(env, filePath, JNI_FALSE);  LOGI("nativeSetUri(), uri = %s", uri);}/* * Class: com_rk_myapp_MainActivity * Method: nativeGetFrameBitmap * Signature: ()Landroid/graphics/Bitmap; */JNIEXPORT jobject JNICALL Java_com_rk_myapp_MainActivity_nativeGetFrameBitmap(JNIEnv *env, jobject obj){  LOGI("nativeGetFrameBitmap()");  return bitmapObj;}/* * Class: com_rk_myapp_MainActivity * Method: nativePrepare * Signature: ()V */JNIEXPORT void JNICALL Java_com_rk_myapp_MainActivity_nativePrepare(JNIEnv *env, jobject obj){  LOGI("nativePrepare()");  // Open video file.  if (avformat_open_input(&pFormatCtx, uri, NULL, NULL) != 0)  {  LOGI("nativePrepare(), Couldn't open file.");  return; // Couldn't open file.  }  // Retrieve stream information.  if (avformat_find_stream_info(pFormatCtx, NULL) < 0)  {  LOGI("nativePrepare(), Couldn't find stream information.");  return; // Couldn't find stream information.  }  // Dump information about file onto standard error.  av_dump_format_for_android(pFormatCtx, 0, uri, 0);  // Find the first video stream.  for (i = 0; i < pFormatCtx->nb_streams; i++)  {  if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)  {  videoStream = i;  break;  }  }  if (videoStream == -1)  {  LOGI("nativePrepare(), Didn't find a video stream.");  return; // Didn't find a video stream.  }  LOGI("nativePrepare(), find all stream num = %d", pFormatCtx->nb_streams);  // Get a pointer to the codec context for the video stream.  pCodecCtxOrig = pFormatCtx->streams[videoStream]->codec;  // Find the decoder for the video stream.  pCodec = avcodec_find_decoder(pCodecCtxOrig->codec_id);  if (pCodec == NULL)  {  LOGI("nativePrepare(), Unsupported codec!");  return; // Codec not found.  }  // Copy context.  pCodecCtx = avcodec_alloc_context3(pCodec);  if (avcodec_copy_context(pCodecCtx, pCodecCtxOrig) != 0)  {  LOGI("nativePrepare(), Couldn't copy codec context");  return; // Error copying codec context.  }  // Open codec.  if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)  {  LOGI("nativePrepare(), Could not open codec.");  return; // Could not open codec.  }  // Allocate video frame.  pFrame = av_frame_alloc();  // Allocate an AVFrame structure.  pFrameRGB = av_frame_alloc();  if (pFrameRGB == NULL)  {  LOGI("nativePrepare(), Could not alloc for pFrameRGB.");  return;  }  // Determine required buffer size and allocate buffer.  numBytes = av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height, 1);  buffer = (uint8_t *) av_malloc(numBytes * sizeof(uint8_t));  // Assign appropriate parts of buffer to image planes in pFrameRGB  //Note that pFrameRGB is an AVFrame, but AVFrame is a superset of AVPicture  //avpicture_fill((AVPicture *)pFrameRGB, buffer, AV_PIX_FMT_RGB24, pCodecCtx->width, pCodecCtx->height); // Deprecated.  av_image_fill_arrays(pFrameRGB->data, pFrameRGB->linesize, buffer, AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height, 1);  // Initialize SWS context for software scaling.  sws_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_RGBA, SWS_BILINEAR, NULL, NULL, NULL);}void createBitmap_for_android(JNIEnv *env, AVFrame *pFrame, int width, int height){  LOGI("createBitmap_for_android(), bitmap width = %d, height = %d", width, height);  /*  jclass bitmapConfig = (*env)->FindClass(env, "android/graphics/Bitmap$Config");  jfieldID argb8888FieldID = (*env)->GetStaticFieldID(env, bitmapConfig, "ARGB_8888", "Landroid/graphics/Bitmap$Config;");  jobject argb8888Obj = (*env)->GetStaticObjectField(env, bitmapConfig, argb8888FieldID);  */  // create bitmap config  // NOTE: c++, use the format " env->FindClass("android/graphics/Bitmap$Config") "  // c, use the format " (*env)->FindClass(env, "android/graphics/Bitmap$Config") "  jclass bitmapConfig = (*env)->FindClass(env, "android/graphics/Bitmap$Config");  jmethodID argbGetValueMethodID = (*env)->GetStaticMethodID(env, bitmapConfig, "valueOf", "(Ljava/lang/String;)Landroid/graphics/Bitmap$Config;");  jobject argbObj = (*env)->CallStaticObjectMethod(env, bitmapConfig, argbGetValueMethodID, (*env)->NewStringUTF(env, "ARGB_8888"));  LOGI("test 1");  // create bitmap  jclass bitmapClass = (*env)->FindClass(env, "android/graphics/Bitmap");  jmethodID createBitmapMethodID = (*env)->GetStaticMethodID(env, bitmapClass, "createBitmap", "(IILandroid/graphics/Bitmap$Config;)Landroid/graphics/Bitmap;");  jmethodID copyByteMethodID = (*env)->GetMethodID(env, bitmapClass, "copyPixelsFromBuffer","(Ljava/nio/Buffer;)V");  LOGI("test 2");  // NOTE: don't leave the "env" arg  // Althought there is not compiling error, the code will run error, if leave out the "env" arg.  jobject bitmapObjLocal = (*env)->CallStaticObjectMethod(env, bitmapClass, createBitmapMethodID, width, height, argbObj);  LOGI("test 3");  // Note: there use global reference, otherwise we not get the local object in JAVA layer and  // there will be a "JNI DETECTED ERROR IN APPLICATION: use of deleted .." error.  bitmapObj = (*env)->NewGlobalRef(env, bitmapObjLocal);  jclass byteBufferClass = (*env)->FindClass(env, "java/nio/ByteBuffer");  jmethodID wrapBufferMethodID = (*env)->GetStaticMethodID(env, byteBufferClass, "wrap", "([B)Ljava/nio/ByteBuffer;");  LOGI("test 4");  //image data to byte array  jbyteArray array = (*env)->NewByteArray(env, width * height * 4);  (*env)->SetByteArrayRegion(env, array, 0, width * height * 4, (jbyte *)(pFrame->data[0]));  jobject byteBufferObj = (*env)->CallStaticObjectMethod(env, byteBufferClass, wrapBufferMethodID, array);  LOGI("test 5");  //NOTE: because method "copyPixelsFromBuffer" return void, so call "CallVoidMethod".  //(*env)->CallObjectMethod(env, bitmapObj, copyByteMethodID, byteBufferObj);  (*env)->CallVoidMethod(env, bitmapObj, copyByteMethodID, byteBufferObj);  LOGI("test 6");}/* * Class: com_rk_myapp_MainActivity * Method: nativeStart * Signature: ()V */JNIEXPORT void JNICALL Java_com_rk_myapp_MainActivity_nativeStart(JNIEnv *env, jobject obj){  LOGI("nativeStart()");  // Read frames and save first five frames to disk.  i = 0;  int frame = 10;  while (av_read_frame(pFormatCtx, &packet) >= 0)  {  LOGI("test 7");  // Is this a packet from the video stream?  if (packet.stream_index == videoStream)  {  // Decode video frame  avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);  // Did we get a video frame?  if (frameFinished)  {  // Convert the image from its native format to RGB.  sws_scale(sws_ctx, (uint8_t const * const *) pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);  // Save the frame to disk.  if (++i == frame)  {  //TODO: save the frame.  createBitmap_for_android(env, pFrameRGB, pCodecCtx->width, pCodecCtx->height);  av_packet_unref(&packet);  break;  }  else  {  frameFinished = 0;  }  }  }  // Free the packet that was allocated by av_read_frame.  //av_free_packet(&packet); // Deprecated.  LOGI("test 8");  av_packet_unref(&packet);  LOGI("test 9");  }}/* * Class: com_rk_myapp_MainActivity * Method: nativeDeinit * Signature: ()V */JNIEXPORT void JNICALL Java_com_rk_myapp_MainActivity_nativeDeinit(JNIEnv *env, jobject obj){  LOGI("nativeDeinit()");  // Free the RGB image.  av_free(buffer);  av_frame_free(&pFrameRGB);  // Free the YUV frame.  av_frame_free(&pFrame);  // Close the codecs.  avcodec_close(pCodecCtx);  avcodec_close(pCodecCtxOrig);  // Close the video file.  avformat_close_input(&pFormatCtx);}

2. jni目录下创建Android.mk和Application.mk文件

Android.mk:

LOCAL_PATH := $(call my-dir)# FFmpeg libraryinclude $(CLEAR_VARS)LOCAL_MODULE := avcodecLOCAL_SRC_FILES := lib/libavcodec-57.soinclude $(PREBUILT_SHARED_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := avfilterLOCAL_SRC_FILES := lib/libavfilter-6.soinclude $(PREBUILT_SHARED_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := avformatLOCAL_SRC_FILES := lib/libavformat-57.soinclude $(PREBUILT_SHARED_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := avutilLOCAL_SRC_FILES := lib/libavutil-55.soinclude $(PREBUILT_SHARED_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := swresampleLOCAL_SRC_FILES := lib/libswresample-2.soinclude $(PREBUILT_SHARED_LIBRARY)include $(CLEAR_VARS)LOCAL_MODULE := swscaleLOCAL_SRC_FILES := lib/libswscale-4.soinclude $(PREBUILT_SHARED_LIBRARY)# Programinclude $(CLEAR_VARS)LOCAL_MODULE := FFMpegJniLOCAL_SRC_FILES := com_rk_myapp_MainActivity.cLOCAL_C_INCLUDES += $(LOCAL_PATH)/includeLOCAL_LDLIBS := -llog -lzLOCAL_SHARED_LIBRARIES := avcodec avfilter avformat avutil swresample swscaleinclude $(BUILD_SHARED_LIBRARY)

Application.mk

APP_ABI=armeabi

4.2 使用NDK编译native源码

1. 配置编译工具目录，在".bashrc"文件中最后一行为PATH变量添加NDK路径

export ANDROID_NATIVE=~/Android/android-ndk-r14bexport PATH=$PATH:$ANDROID_NATIVE

2. 在Android工程目录下运行命令编译native源码

ndk-build

3. 在Android工程下libs/armeabi目录下生成相应so库文件

4. 在Android工程下运行命令，生成apk，所生成的apk在Android工程的bin目录下，我的apk为MyFirstApp-debug.apk

ant debug