FFmpeg解码视频帧为jpg图片保存到本地

来源：互联网发布：python 图形化界面编辑：程序博客网时间：2024/06/03 15:58

    之前遇到一个需求是将视频一秒一秒解码成一帧一帧的图片，用户滑动选择时间节点（微信朋友圈发10秒视频的编辑界面）。开始我是用的MediaMetadataRetriever类来获取图片，但是对于分辨率比较大的视频（1920*1080）获取一个图片要0.7/0.8秒，太慢了。后来又用FFmpeg的命令来批量的解码视频成一帧一帧的图片，速度依然不快每张图片得耗费0.5秒左右的时间。最后还是用FFmpeg，不过不是用命令行，而是用NDK，发现c解码视频再转换为图片保存起来效率大大挺高，一秒钟能解码4、5张图片，c就是快啊，做一下总结。

附上源码：
http://download.csdn.net/download/qq_28284547/10031785
GitHub：https://github.com/kui92/FFmpegTools

    创建工程，注意要勾选上支持c++。

这里写图片描述

我从网上找到了编译好的FFmpeg文件，直接考到自己的工程里的。

配置gradle与CMakeLists
gradle

CMakeLists

cmake_minimum_required(VERSION 3.4.1)
include_directories(
${CMAKE_SOURCE_DIR}/src/main/cpp/include
)

add_library( # Sets the name of the library.
jxffmpegrun

         # Sets the library as a shared library.         SHARED         # Provides a relative path to your source file(s).          src/main/cpp/cmdutils.c          src/main/cpp/ffmpeg.c          src/main/cpp/ffmpeg_filter.c          src/main/cpp/ffmpeg_opt.c          src/main/cpp/jx_ffmpeg_cmd_run.c         )

add_library(avcodec SHARED IMPORTED)

add_library(avfilter SHARED IMPORTED)

add_library(avformat SHARED IMPORTED)

add_library(avutil SHARED IMPORTED)

add_library(swresample SHARED IMPORTED)

add_library(swscale SHARED IMPORTED)

add_library(fdk-aac SHARED IMPORTED)

set_target_properties(
avcodec
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libavcodec.so
)

set_target_properties(
avfilter
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libavfilter.so
)

set_target_properties(
avformat
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libavformat.so
)

set_target_properties(
avutil
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libavutil.so
)

set_target_properties(
swresample
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libswresample.so
)

set_target_properties(
swscale
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libswscale.so
)

set_target_properties(
fdk-aac
PROPERTIES IMPORTED_LOCATION
CMAKESOURCEDIR/src/main/jniLibs/{ANDROID_ABI}/libfdk-aac.so
)

target_link_libraries( # Specifies the target library.
jxffmpegrun
log
android
fdk-aac
avcodec
avfilter
avformat
avutil
swresample
swscale
# Links the target library to the log library
# included in the NDK.
${log-lib} )

新建FfmpegTool类，编写native方法并生成头文件（头文件的生成方法可自行百度）

这里写图片描述

实现native方法

//实现native方法#define  LOG_TAG    "videoplayer"#define  LOGD(...)  __android_log_print(ANDROID_LOG_DEBUG, LOG_TAG, __VA_ARGS__)/** * 将AVFrame(YUV420格式)保存为JPEG格式的图片 * * @param width YUV420的宽 * @param height YUV42的高 * */int MyWriteJPEG(AVFrame *pFrame,char *path,  int width, int height, int iIndex) {    // 输出文件路径    char out_file[1000] = {0};    LOGD("path:%s", path);    sprintf(out_file, "%stemp%d.jpg", path, iIndex);    LOGD("out_file:%s", out_file);    // 分配AVFormatContext对象    AVFormatContext *pFormatCtx = avformat_alloc_context();    // 设置输出文件格式    pFormatCtx->oformat = av_guess_format("mjpeg", NULL, NULL);    // 创建并初始化一个和该url相关的AVIOContext    if (avio_open(&pFormatCtx->pb, out_file, AVIO_FLAG_READ_WRITE) < 0) {        LOGD("Couldn't open output file.");        return -1;    }    // 构建一个新stream    AVStream *pAVStream = avformat_new_stream(pFormatCtx, 0);    if (pAVStream == NULL) {        return -1;    }    // 设置该stream的信息    AVCodecContext *pCodecCtx = pAVStream->codec;    pCodecCtx->codec_id = pFormatCtx->oformat->video_codec;    pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;    pCodecCtx->pix_fmt = AV_PIX_FMT_YUVJ420P;    pCodecCtx->width = width;    pCodecCtx->height = height;    pCodecCtx->time_base.num = 1;    pCodecCtx->time_base.den = 25;    // Begin Output some information    av_dump_format(pFormatCtx, 0, out_file, 1);    // End Output some information    // 查找解码器    AVCodec *pCodec = avcodec_find_encoder(pCodecCtx->codec_id);    if (!pCodec) {        LOGD("Codec not found.");        return -1;    }    // 设置pCodecCtx的解码器为pCodec    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {        LOGD("Could not open codec.");        return -1;    }    //Write Header    avformat_write_header(pFormatCtx, NULL);    int y_size = pCodecCtx->width * pCodecCtx->height;    //Encode    // 给AVPacket分配足够大的空间    AVPacket pkt;    av_new_packet(&pkt, y_size * 3);    //    int got_picture = 0;    int ret = avcodec_encode_video2(pCodecCtx, &pkt, pFrame, &got_picture);    if (ret < 0) {        LOGD("Encode Error.\n");        return -1;    }    if (got_picture == 1) {        //pkt.stream_index = pAVStream->index;        ret = av_write_frame(pFormatCtx, &pkt);    }    av_free_packet(&pkt);    //Write Trailer    av_write_trailer(pFormatCtx);    LOGD("Encode Successful.\n");    if (pAVStream) {        avcodec_close(pAVStream->codec);    }    avio_close(pFormatCtx->pb);    avformat_free_context(pFormatCtx);    return 0;}/** *方法的实现入口 */JNIEXPORT jint JNICALL Java_com_esay_ffmtool_FfmpegTool_decodToImage        (JNIEnv * env, jclass mclass, jstring in, jstring dir, jint startTime, jint num){    char * input=jstringTostring(env,in);    char * parent=jstringTostring(env,dir);    LOGD("input:%s",input);    LOGD("parent:%s",parent);    av_register_all();    AVFormatContext *pFormatCtx = avformat_alloc_context();    // Open video file    if (avformat_open_input(&pFormatCtx, input, NULL, NULL) != 0) {        LOGD("Couldn't open file:%s\n", input);        return -1; // Couldn't open file    }    // Retrieve stream information    if (avformat_find_stream_info(pFormatCtx, NULL) < 0) {        LOGD("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) {        LOGD("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) {        LOGD("Codec not found.");        return -1; // Codec not found    }    if (avcodec_open2(pCodecCtx, pCodec, NULL) < 0) {        LOGD("Could not open codec.");        return -1; // Could not open codec    }    // Allocate video frame    AVFrame *pFrame = av_frame_alloc();    if (pFrame == NULL) {        LOGD("Could not allocate video frame.");        return -1;    }    int64_t count = startTime;    int frameFinished;    //(*pCodecCtx).    AVPacket packet;    LOGD("start_time:%d",pFormatCtx->start_time);    LOGD("pFormatCtx den:%d", pFormatCtx->streams[videoStream]->sample_aspect_ratio.den);    LOGD("pFormatCtx num:%d", pFormatCtx->streams[videoStream]->sample_aspect_ratio.num);    av_seek_frame(pFormatCtx,-1,(int64_t)count*AV_TIME_BASE,AVSEEK_FLAG_FRAME);    while (av_read_frame(pFormatCtx, &packet) >= 0){        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){                if(count<(startTime+num)){                    MyWriteJPEG(pFrame,parent, pCodecCtx->width,                                pCodecCtx->height, count);                    ++count;                    av_seek_frame(pFormatCtx,-1,(int64_t)count*AV_TIME_BASE,AVSEEK_FLAG_FRAME);                } else{                    av_packet_unref(&packet);                    LOGD("break:");                    break;                }            }        }        av_packet_unref(&packet);    }    // Free the YUV frame    av_free(pFrame);    // Close the codecs    avcodec_close(pCodecCtx);    // Close the video file    avformat_close_input(&pFormatCtx);    return  0;}

链接so库，在类FfmpegTool开头加入代码：

 static {        System.loadLibrary("avutil");        System.loadLibrary("fdk-aac");        System.loadLibrary("avcodec");        System.loadLibrary("avformat");        System.loadLibrary("swscale");        System.loadLibrary("swresample");        System.loadLibrary("avfilter");        System.loadLibrary("jxffmpegrun");    }

//测试运行,在MainActivity中添加按钮执行如下方法，注意FfmpegTool.decodToImage方法是阻塞的，有时候耗时较长要放在子线程。public void click2(View view){        String path= "图片要保存的路径";        String video="视频路径";        FfmpegTool.decodToImage(video,path,0,60);    }

最后再次附上源码：
http://download.csdn.net/download/qq_28284547/10031785
GitHub：https://github.com/kui92/FFmpegTools

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