NDK--利用FFmpeg进行视频解码

package com.aruba.ffmpegapplication;

import android.os.Bundle;
import android.os.Environment;
import android.view.View;

import androidx.appcompat.app.AppCompatActivity;

import java.io.File;

public class MainActivity extends AppCompatActivity {

    static {
        System.loadLibrary("native-lib");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

    }

    public native void decode(String inputFilePath, String outputFilePath);

    public void click(View view) {
        File input = new File(Environment.getExternalStorageDirectory(), "input.mp4");
        File output = new File(Environment.getExternalStorageDirectory(), "output.yuv");
        decode(input.getAbsolutePath(), output.getAbsolutePath());
    }
}

#include <jni.h>
#include <string>
#include <android/log.h>

extern "C" {
//编码
#include "libavcodec/avcodec.h"
//封装格式处理
#include "libavformat/avformat.h"
//像素处理
#include "libswscale/swscale.h"
}

#define  LOG_TAG    "aruba"
#define  LOGE(...)  __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__)

extern "C"
JNIEXPORT void JNICALL
Java_com_aruba_ffmpegapplication_MainActivity_decode(JNIEnv *env, jobject instance,
                                                     jstring inputFilePath_,
                                                     jstring outputFilePath_) {
    const char *inputFilePath = env->GetStringUTFChars(inputFilePath_, 0);
    const char *outputFilePath = env->GetStringUTFChars(outputFilePath_, 0);

    //注册FFmpeg中各大组件
    av_register_all();

    //打开文件
    AVFormatContext *formatContext = avformat_alloc_context();
    if (avformat_open_input(&formatContext, inputFilePath, NULL, NULL) != 0) {
        LOGE("打开失败");
        avformat_free_context(formatContext);
        env->ReleaseStringUTFChars(inputFilePath_, inputFilePath);
        env->ReleaseStringUTFChars(outputFilePath_, outputFilePath);
        return;
    }

    //将文件信息填充进AVFormatContext
    if (avformat_find_stream_info(formatContext, NULL) < 0) {
        LOGE("获取文件信息失败");
        avformat_free_context(formatContext);
        env->ReleaseStringUTFChars(inputFilePath_, inputFilePath);
        env->ReleaseStringUTFChars(outputFilePath_, outputFilePath);
        return;
    }

    //获取视频流的编解码器上下文
    AVCodecContext *codecContext = NULL;
    for (int i = 0; i < formatContext->nb_streams; ++i) {
        if (formatContext->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {//如果是视频流
            codecContext = formatContext->streams[i]->codec;
            break;
        }
    }

    if (codecContext == NULL) {
        avformat_free_context(formatContext);
        env->ReleaseStringUTFChars(inputFilePath_, inputFilePath);
        env->ReleaseStringUTFChars(outputFilePath_, outputFilePath);
        return;
    }

    //根据编解码器上下文的id获取视频流解码器
    AVCodec *codec = avcodec_find_decoder(codecContext->codec_id);
    //打开解码器
    if (avcodec_open2(codecContext, codec, NULL) < 0) {
        LOGE("解码失败");
        avformat_free_context(formatContext);
        env->ReleaseStringUTFChars(inputFilePath_, inputFilePath);
        env->ReleaseStringUTFChars(outputFilePath_, outputFilePath);
        return;
    }

    //开始读每一帧
    //存放压缩数据
    AVPacket *pkt = (AVPacket *) (av_malloc(sizeof(AVPacket)));
    av_init_packet(pkt);

    //存放解压数据
    AVFrame *picture = av_frame_alloc();

    //存放转码数据
    AVFrame *picture_yuv = av_frame_alloc();
    //为转码数据分配内存
    uint8_t *data_size = (uint8_t *) (av_malloc(
            (size_t) avpicture_get_size(AV_PIX_FMT_YUV420P, codecContext->width,
                                        codecContext->height)));
    avpicture_fill((AVPicture *) picture_yuv, data_size, AV_PIX_FMT_YUV420P, codecContext->width,
                   codecContext->height);

    int picture_ptr = 0;

    //转码组件上下文,前三个参数为原视频的宽高和编码，后三个为转码后的视频宽高和编码，还可以传入过滤器对视频做处理，这边不做处理
    SwsContext *swsContext = sws_getContext(codecContext->width, codecContext->height,
                                            codecContext->pix_fmt,
                                            codecContext->width, codecContext->height,
                                            AV_PIX_FMT_YUV420P, SWS_BILINEAR, NULL, NULL, NULL
    );

    //文件
    FILE *output_file = fopen(outputFilePath, "wb");

    while (av_read_frame(formatContext, pkt) == 0) {//读到每一帧的压缩数据存放在AVPacket

        //解码
        avcodec_decode_video2(codecContext, picture, &picture_ptr, pkt);

        if (picture_ptr > 0) {
            LOGE("picture_ptr %d", picture_ptr);

            //转码 data中存放着真实数据，linesize为一行的数据，0为转码起始位置，高度为整个画面高
            sws_scale(swsContext, picture->data, picture->linesize, 0, picture->height,
                      picture_yuv->data, picture_yuv->linesize);

            //一帧的数据大小
            size_t size_y = codecContext->width * codecContext->height;
            //写文件 y:u:v为4：1：1
            //写y
            fwrite(picture_yuv->data[0], sizeof(uint8_t), size_y, output_file);
            //写u
            fwrite(picture_yuv->data[1], sizeof(uint8_t), size_y / 4, output_file);
            //写v
            fwrite(picture_yuv->data[2], sizeof(uint8_t), size_y / 4, output_file);
        }

        av_free_packet(pkt);
    }

    //关闭文件
    fclose(output_file);
    //释放资源
    sws_freeContext(swsContext);
    av_frame_free(&picture_yuv);
    av_frame_free(&picture);
    avcodec_close(codecContext);
    avformat_free_context(formatContext);
    env->ReleaseStringUTFChars(inputFilePath_, inputFilePath);
    env->ReleaseStringUTFChars(outputFilePath_, outputFilePath);
}