一、背景

本demo主要介绍android调用ffmpeg中的接口解析rtsp协议的视频流（不解析音频），得到yuv数据，把yuv转bitmap在android设备上显示，涉及到打开视频、解封装、解码、回调yuv数据。学习记录帖，C语言小白，不足的地方请指正，多谢！

二、解析rtsp数据

1、C层功能代码

Decoder.h

#ifndef DECODERTSP_DECODER_H
#define DECODERTSP_DECODER_H
#include <thread>
#include "include/jniLog.h"
extern "C"
{
#include <libavutil/time.h>
#include <libavcodec/avcodec.h>
#include <libavcodec/packet.h>
#include <libavutil/imgutils.h>
#include <libswscale/swscale.h>
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
#include <libavutil/opt.h>
#include <functional>
};

using namespace std;
// 定义一个回调函数类型（typedef 用于为已有的数据类型创建一个别名）
typedef std::function<void(uint8_t *buf, int size)> Callback;

// 解析rtsp视频流
int ReadFrameAndDecoder(const char *url,Callback callback);
void DoStop();
#endif //DECODERTSP_DECODER_H

Decoder.cpp

#include "include/Decoder.h"
#include "include/jniLog.h"
bool isStop = false;
int ReadFrameAndDecoder(const char* m_Url,Callback callback){
    char url[100] = {0};
    strcpy(url,m_Url);
    AVFormatContext *pFormatCtx = avformat_alloc_context();

    AVDictionary *options = NULL;
    av_dict_set(&options, "buffer_size", "1024000", 0);// 设置缓冲区大小
    av_dict_set(&options, "stimeout", "20000000", 0);
    av_dict_set(&options, "max_delay", "30000000", 0);
//    av_dict_set(&options, "rtsp_transport", "tcp", 0); //使用 TCP 传输

    LOGI("ReadFrameAndDecoder:url = %s",url);
    if (avformat_open_input(&pFormatCtx, url, NULL, NULL) != 0)     // 打开视频文件
        return -1;

    if (avformat_find_stream_info(pFormatCtx, NULL) < 0)    // 查找视频流
        return -2;

    //视频解码，需要找到视频对应的AVStream所在pFormatCtx->streams的索引位置
    int video_stream_idx = -1;
    for (int i = 0; i < pFormatCtx->nb_streams; i++) {
        //根据类型判断，是否是视频流
        if (pFormatCtx->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
            video_stream_idx = i;
            break;
        }
    }

    //只有知道视频的编码方式，才能够根据编码方式去找到解码器
    //获取视频流中的编解码上下文
    AVCodecContext *pCodecCtx = avcodec_alloc_context3(NULL);;
    avcodec_parameters_to_context(pCodecCtx, pFormatCtx->streams[video_stream_idx]->codecpar);
    // AVDISCARD_NONKEY;  // 丢弃非关键帧(如B帧)
    // AVDISCARD_NONINTRA;  // 丢弃所有非帧内编码的帧(这个参数不会灰屏)
    // AVDISCARD_NONREF     // 丢弃所有非参考帧
    // AVDISCARD_BIDIR      // 丢弃所有双向预测帧
    //  AVDISCARD_DEFAULT
//    pCodecCtx->skip_frame = AVDISCARD_NONKEY;

    //4.根据编解码上下文中的编码id查找对应的解码
    //AVCodec *pCodec = const_cast<AVCodec *>(avcodec_find_decoder(pCodecCtx->codec_id));
    AVCodec *pCodec = const_cast<AVCodec *>(avcodec_find_decoder(AV_CODEC_ID_HEVC));
    if (pCodec == NULL)
        return -3;

    // 打开解码器
    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0)
        return -4;

    // 设置参数(不缓冲，低延时)
//    av_opt_set(pCodecCtx->priv_data, "tune", "zerolatency", 0);
//    pCodecCtx->flags |= AV_CODEC_FLAG_LOW_DELAY;

    // 分配视频帧(装载解码后的数据)
    AVFrame *pFrame = av_frame_alloc();
    AVPacket packet; // 读取视频帧(解码前的数据包)
    while (av_read_frame(pFormatCtx, &packet) >= 0 && !isStop) {
        if (packet.stream_index == video_stream_idx) {
            int got_picture;
            // 向解码器输入数据包
            got_picture = avcodec_send_packet(pCodecCtx, &packet);
            if (got_picture < 0) {
                LOGI("got_picture = %d", got_picture);
                continue;
            }
            while (got_picture == 0) {
                // 从解码器获取帧  返回值 -11：数据包不足？
                got_picture = avcodec_receive_frame(pCodecCtx, pFrame);
                //此时，pFrame中的数据就是YUV数据
                if(got_picture == 0){
                    // 计算 frame 的数据大小
                    int data_size = av_image_get_buffer_size(AV_PIX_FMT_YUV420P, pFrame->width, pFrame->height, 1);
                    if (data_size < 0) {
                        LOGE("Could not calculate buffer size");
                        return -5;
                    }

                    // 分配内存来存储 byte[]
                    uint8_t *buffer = (uint8_t *)av_malloc(data_size * sizeof(uint8_t));
                    if (!buffer) {
                        LOGE("Could not allocate memory for buffer");
                        return -6;
                    }

                    // 将 AVFrame 的数据复制到 buffer 中
                    int ret = av_image_copy_to_buffer(buffer, data_size,
                                                      (const uint8_t * const *)pFrame->data, pFrame->linesize,
                                                      AV_PIX_FMT_YUV420P, pFrame->width, pFrame->height, 1);
                    if (ret < 0) {
                        LOGE("Could not copy image data to buffer");
                        av_free(buffer);
                        return -7;
                    }

                    if (callback){
                        callback(buffer,data_size * sizeof(uint8_t));
                    }
                    // 释放 buffer
                    av_free(buffer);
                }else{
                    LOGI("avcodec_receive_frame # got_picture = %d", got_picture);
                }
            }
        }
        av_packet_unref(&packet);
    }

    // 释放资源
    av_frame_free(&pFrame);
    avcodec_close(pCodecCtx);
    avformat_close_input(&pFormatCtx);
    return 0;
}

void DoStop(){
    isStop = true;
}

2、jni层的定义

native-lib.cpp

#include <jni.h>
#include <string>
#include <include/jniLog.h>
#include "include/Decoder.h"

extern "C"
JNIEXPORT jint JNICALL
Java_com_hisign_decodertsp_DecodeLib_native_1readAndDecode(JNIEnv *env, jobject thiz,
                                                           jstring rtsp_url) {
    // TODO: implement native_readAndDecode()
    const char *url = env->GetStringUTFChars(rtsp_url, nullptr);
    LOGI("url = %s", url);
    // java层的回调函数
    jmethodID mid = env->GetMethodID(env->GetObjectClass(thiz), "packetEventCallback", "([B)V");

    if(!mid){
        LOGI("StartRestAndDecodePackage, mid is null");
    }
    // 获取java层的回调函数
    Callback dataCallback = [&env, &mid, &thiz](uint8_t *buf, int size){
        // todo 通过jni调用java层返回数据
        if(mid != nullptr){
            jbyteArray  array1 = env->NewByteArray(size);
            env->SetByteArrayRegion(array1,0,size,(jbyte*)buf);
            env->CallVoidMethod(thiz, mid, array1);
            env->DeleteLocalRef(array1);
        }
    };
    int ret = ReadFrameAndDecoder(url,dataCallback);
    LOGI("ReadFrameAndDecoder ret = %d",ret);
    env->ReleaseStringUTFChars(rtsp_url, url);
    return 0;
}

extern "C"
JNIEXPORT jint JNICALL
Java_com_hisign_decodertsp_DecodeLib_native_1Stop(JNIEnv *env, jobject thiz) {

    // TODO: implement native_Stop()
    DoStop();
    return 0;
}

3、app层的调用

public class DecodeLib {
    static {
        System.loadLibrary("decodertsp");
    }

    private EventCallback mEventCallback = null;

    // 开始解码
    public void start(String url) {
        native_readAndDecode(url);
    }

    public void stop() {
        native_Stop();
    }

    public void addEventCallback(EventCallback callback) {
        mEventCallback = callback;
    }
    // 被native层回调
    private void packetEventCallback(byte[] data) {
        if (mEventCallback != null)
            mEventCallback.onReceiveData(data);
    }

    // 测试读取视频帧并解码
    private native int native_readAndDecode(String rtsp_url);

    private native int native_Stop();

    /**
     * 返回yuv数据
     */
    public interface EventCallback {
        void onReceiveData(byte[] yuv);
    }
}

MainActivity.java

public class MainActivity extends AppCompatActivity {
    private final static String KEY_IP  = "KEY_IP";
    private static int width = 1920;
    private static int height = 1080;
    private ActivityMainBinding binding;
    private DecodeLib decodeLib;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        binding = ActivityMainBinding.inflate(getLayoutInflater());
        setContentView(binding.getRoot());
        decodeLib = new DecodeLib();
        String ip = SPUtils.getInstance().getString(KEY_IP);
        binding.etIp.setText(ip);
        binding.btnStart.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String ip = binding.etIp.getText().toString();
                if(TextUtils.isEmpty(ip)){
                    Toast.makeText(MainActivity.this, "please input ip!", Toast.LENGTH_SHORT).show();
                    return;
                }
                SPUtils.getInstance().put(KEY_IP,ip);
                String url = "rtsp://"+ip+":554/livestream/0";
                new Thread(){
                    public void run(){
                        startRtsp(url);
                    }
                }.start();
                KeyboardUtils.hideSoftInput(MainActivity.this);
            }
        });

        binding.btnStop.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                decodeLib.stop();
            }
        });
    }

    private void startRtsp(String url){
        decodeLib.addEventCallback(new DecodeLib.EventCallback() {
            @Override
            public void onReceiveData(byte[] yuv) {
                // todo 这里显示图片
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        Bitmap bmp = YuvToBitmapConverter.i420ToBitmap(yuv, width, height);
                        if(bmp != null){
                            binding.img.setImageBitmap(bmp);
                        }
                    }
                });
            }
        });
        decodeLib.start(url);
    }
}

三、源码下载

https://download.csdn.net/download/dami_lixm/90408495?spm=1001.2014.3001.5503