Android Multimedia框架总结（二十六）利用FFmpeg进行解码直播流

早在去年九月份时，写过一篇《手把手图文并茂教你用Android Studio编译FFmpeg库并移植，今天用去年编译好的3.1.3的ffmpeg，进行在Android平台上解码直播流。看下Agenda:

• 环境
• Java代码
• ndk代码
• 解码运行

环境：

• Mac OX
• Android Studio 2.2
• android-ndk-r10e
• FFmpeg 3.1.3

Android Studio + NDK的环境配置，由于很简单，这里就不再脑补了。

建立一个工程

写Java代码：

NativePlayer:

生成头文件：javah -d jni com.hejunlin.ffmpegdecoder.NativePlayer

拷贝ffmpeg3.1.3中android目录下的include文件，共5个子文件夹，以及对应的5个so，到prebuilt下，include,prebuilt这个可以自己建立一个folder。

然后写make文件：

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := avcodec
LOCAL_SRC_FILES := prebuilt/libavcodec-57.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := avformat
LOCAL_SRC_FILES := prebuilt/libavformat-57.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := avutil
LOCAL_SRC_FILES := prebuilt/libavutil-55.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := swresample
LOCAL_SRC_FILES := prebuilt/libswresample-2.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := swscale
LOCAL_SRC_FILES := prebuilt/libswscale-4.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

LOCAL_SRC_FILES := yuiopffmpeg.c
LOCAL_LDLIBS += -llog -lz -landroid
LOCAL_MODULE := yuiopffmpeg
LOCAL_C_INCLUDES += $(LOCAL_PATH)/include

LOCAL_SHARED_LIBRARIES:= avcodec avformat avutil swresample swscale

include $(BUILD_SHARED_LIBRARY)

同时写下Application.mk，这个主要是用于编译不同平台的库，对应内容如下,由于引用了native_window.h，要加上一句APP_PLATFORM := android-10 ：

APP_ABI := armeabi armeabi-v7a x86
APP_PLATFORM := android-10 

接下来，最主要就是写jni相关代码，yuiopffmpeg.c这个文件，之前生成的那个头文件，拷贝里面那个方法名，贴到这里来

#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include <android/native_window.h>
#include <android/native_window_jni.h>
#include "com_hejunlin_ffmpegdecoder_NativePlayer.h"
#include "log.h"
JNIEXPORT jint JNICALL Java_com_hejunlin_ffmpegdecoder_NativePlayer_playVideo
        (JNIEnv * env, jclass clazz, jstring url, jobject surface)
{
    LOGD("start playvideo... url");
    const char * file_name  = (*env)->GetStringUTFChars(env, url, JNI_FALSE);
    av_register_all();
    AVFormatContext * pFormatCtx = avformat_alloc_context();
    // Open video file
    if(avformat_open_input(&pFormatCtx, file_name, NULL, NULL)!=0) {
        LOGE("Couldn't open file:%s\n", file_name);
        return -1; // Couldn't open file
    }
    // Retrieve stream information
    if(avformat_find_stream_info(pFormatCtx, NULL)<0) {
        LOGE("Couldn't find stream information.");
        return -1;
    }
    // Find the first video stream
    int videoStream = -1, i;
    for (i = 0; i < pFormatCtx->nb_streams; i++) {
        if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO
           && videoStream < 0) {
            videoStream = i;
        }
    }
    if(videoStream==-1) {
        LOGE("Didn't find a video stream.");
        return -1; // Didn't find a video stream
    }
    // Get a pointer to the codec context for the video stream
    AVCodecContext  * pCodecCtx = pFormatCtx->streams[videoStream]->codec;
    // Find the decoder for the video stream
    AVCodec * pCodec = avcodec_find_decoder(pCodecCtx->codec_id);
    if(pCodec==NULL) {
        LOGE("Codec not found.");
        return -1; // Codec not found
    }
    if(avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {
        LOGE("Could not open codec.");
        return -1; // Could not open codec
    }
    // 获取native window
    ANativeWindow* nativeWindow = ANativeWindow_fromSurface(env, surface);
    // 获取视频宽高
    int videoWidth = pCodecCtx->width;
    int videoHeight = pCodecCtx->height;
    // 设置native window的buffer大小,可自动拉伸
    ANativeWindow_setBuffersGeometry(nativeWindow,  videoWidth, videoHeight, WINDOW_FORMAT_RGBA_8888);
    ANativeWindow_Buffer windowBuffer;
    if(avcodec_open2(pCodecCtx, pCodec, NULL)<0) {
        LOGE("Could not open codec.");
        return -1; // Could not open codec
    }
    // Allocate video frame
    AVFrame * pFrame = av_frame_alloc();
    // 用于渲染
    AVFrame * pFrameRGBA = av_frame_alloc();
    if(pFrameRGBA == NULL || pFrame == NULL) {
        LOGE("Could not allocate video frame.");
        return -1;
    }
    // Determine required buffer size and allocate buffer
    // buffer中数据就是用于渲染的,且格式为RGBA
    int numBytes=av_image_get_buffer_size(AV_PIX_FMT_RGBA, pCodecCtx->width, pCodecCtx->height, 1);
    uint8_t * buffer=(uint8_t *)av_malloc(numBytes*sizeof(uint8_t));
    av_image_fill_arrays(pFrameRGBA->data, pFrameRGBA->linesize, buffer, AV_PIX_FMT_RGBA,
                         pCodecCtx->width, pCodecCtx->height, 1);
    // 由于解码出来的帧格式不是RGBA的,在渲染之前需要进行格式转换
    struct SwsContext *sws_ctx = sws_getContext(pCodecCtx->width,
                             pCodecCtx->height,
                             pCodecCtx->pix_fmt,
                             pCodecCtx->width,
                             pCodecCtx->height,
                             AV_PIX_FMT_RGBA,
                             SWS_BILINEAR,
                             NULL,
                             NULL,
                             NULL);
    int frameFinished;
    AVPacket packet;
    while(av_read_frame(pFormatCtx, &packet)>=0) {
        // Is this a packet from the video stream?
        if(packet.stream_index==videoStream) {
            // Decode video frame
            avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet);
            // 并不是decode一次就可解码出一帧
            if (frameFinished) {
                // lock native window buffer
                ANativeWindow_lock(nativeWindow, &windowBuffer, 0);
                // 格式转换
                sws_scale(sws_ctx, (uint8_t const * const *)pFrame->data,
                          pFrame->linesize, 0, pCodecCtx->height,
                          pFrameRGBA->data, pFrameRGBA->linesize);
                // 获取stride
                uint8_t * dst = windowBuffer.bits;
                int dstStride = windowBuffer.stride * 4;
                uint8_t * src = (uint8_t*) (pFrameRGBA->data[0]);
                int srcStride = pFrameRGBA->linesize[0];
                // 由于window的stride和帧的stride不同,因此需要逐行复制
                int h;
                for (h = 0; h < videoHeight; h++) {
                    memcpy(dst + h * dstStride, src + h * srcStride, srcStride);
                }
                ANativeWindow_unlockAndPost(nativeWindow);
            }
        }
        av_packet_unref(&packet);
    }
    av_free(buffer);
    av_free(pFrameRGBA);
    // Free the YUV frame
    av_free(pFrame);
    // Close the codecs
    avcodec_close(pCodecCtx);
    // Close the video file
    avformat_close_input(&pFormatCtx);
    return 0;
}

这时就可以执行编译了，完成就能发现会多一个so,就是那个libyuiopffmpeg.so，这就是我编译出来的。

这时候，在Android studio下的main目录下，建立一个jniLibs，把刚刚那个so拷贝到这里就行了，就只要这个so就可以了。不同平台，如arm,x86,这些文件夹名字不能随便改。记得还要加如下配置，在build.gradle中。

接下来就运行这个工程，运行时，又有问题。

然后发现原来没有加网络权限，在AndroidManifest.xml中，加上

 <uses-permission android:name="android.permission.INTERNET" />

最后，就可以运行了，效果图，如下：