Android(安卓)NDK开发之旅37--FFmpeg转码压缩

Android NDK开发之旅目录

前言

Windows下命令行转码压缩形式

ffmpeg -i input.mov -b:v 640k output.mp4

Android也是利用FFmpeg命令行的形式(混编)，进行视频转码压缩。

1.引入FFmpeg命令行调用库

2.Android 核心代码

2.1.jni Java声明

    //视频转码压缩    public native void transcodingCompress(int argc,String[] argv);

2.2.核心代码ffmpeg_transcoding.c

#include "jni.h"#include "ffmpeg.h"//视频转码压缩主函数入口//SDL（main）//ffmpeg_mod.c有一个FFmpeg视频转码主函数入口//标记（声明有一个这样的函数提供给我调用）//参数含义分析//首先分析：String str = "ffmpeg -i input.mov -b:v 640k output.mp4"// argc = str.split(" ").length()// argv = str.split(" ")  字符串数组//参数一：命令行字符串命令个数//参数二：命令行字符串数组int ffmpegmain(int argc, char **argv);JNIEXPORT void JNICALL Java_com_haocai_ffmpegtest_util_VideoPlayer_transcodingCompress        (JNIEnv *env, jobject jobj,jint jlen,jobjectArray jobjArray){    //转码    //将java的字符串数组转成C字符串    int argc = jlen;    //开辟内存空间    char **argv = (char**)malloc(sizeof(char*) * argc);    //填充内容    for (int i = 0; i < argc; ++i) {        jstring str = (*env)->GetObjectArrayElement(env,jobjArray,i);        const char* tem = (*env)->GetStringUTFChars(env,str,0);        argv[i] = (char*)malloc(sizeof(char)*1024);        strcpy(argv[i],tem);    }    //开始转码(底层实现就是只需命令)    ffmpegmain(argc,argv);    //释放内存空间    for (int i = 0; i < argc; ++i) {        free(argv[i]);    }    //释放数组    free(argv);}

调用ffmpeg_mod.c中ffmpegmain函数入口

//ffmpeg主函数入口int ffmpegmain(int argc, char **argv){    int ret;    int64_t ti;    //av_log_set_callback(av_log_callback);     register_exit(ffmpeg_cleanup);    setvbuf(stderr,NULL,_IONBF,0); /* win32 runtime needs this */    av_log_set_flags(AV_LOG_SKIP_REPEATED);    parse_loglevel(argc, argv, options);    if(argc>1 && !strcmp(argv[1], "-d")){        run_as_daemon=1;        av_log_set_callback(log_callback_null);        argc--;        argv++;    }    avcodec_register_all();#if CONFIG_AVDEVICE    avdevice_register_all();#endif    avfilter_register_all();    av_register_all();    avformat_network_init();    show_banner(argc, argv, options);    term_init();    /* parse options and open all input/output files */    ret = ffmpeg_parse_options(argc, argv);    if (ret < 0)    {   ffmpeg_cleanup(1);  return 1;}    if (nb_output_files <= 0 && nb_input_files == 0) {        show_usage();        av_log(NULL, AV_LOG_WARNING, "Use -h to get full help or, even better, run 'man %s'\n", program_name);        ffmpeg_cleanup(1);        return 1;    }    /* file converter / grab */    if (nb_output_files <= 0) {        av_log(NULL, AV_LOG_FATAL, "At least one output file must be specified\n");        ffmpeg_cleanup(1);        return 1;    }//     if (nb_input_files == 0) {//         av_log(NULL, AV_LOG_FATAL, "At least one input file must be specified\n");//         exit_program(1);//     }    current_time = ti = getutime();    if (transcode() < 0)    {    ffmpeg_cleanup(1);  return 1;}    ti = getutime() - ti;     av_log(NULL, AV_LOG_FATAL, "Transcode has Finished\n");  // if (do_benchmark) {   //     printf("bench: utime=%0.3fs\n", ti / 1000000.0);   // }   // av_log(NULL, AV_LOG_DEBUG, "%"PRIu64" frames successfully decoded, %"PRIu64" decoding errors\n",    //       decode_error_stat[0], decode_error_stat[1]);    //if ((decode_error_stat[0] + decode_error_stat[1]) * max_error_rate < decode_error_stat[1])   // {    exit_program(69); return 69;}    ///exit_program(received_nb_signals ? 255 : main_return_code);    ffmpeg_cleanup(0);    return main_return_code;}

2.3调用程序

   public void transcodingCompress(){        final File inputFile;        final File outputFile;        final File dic = Environment.getExternalStorageDirectory();        inputFile = new File(dic,"告白气球.avi");        outputFile = new File(dic,"告白气球.mp4");        new Thread(new Runnable() {            @Override            public void run() {                //获取视频文件的路径(sdcard路径)                // 拼接cmd 指令 ffmpeg -i 告白气球.avi -b:v 640k 告白气球.mp4 (与windows 命令行相同)                StringBuilder builder = new StringBuilder();                builder.append("ffmpeg ");                builder.append("-i ");                builder.append(inputFile.getAbsolutePath()+" ");                builder.append("-b:v 640k ");  //码率越大 清晰度越高 码率越小 清晰度越低                builder.append(outputFile.getAbsolutePath());                String[] argv = builder.toString().split(" ");                int argc = argv.length;                player.transcodingCompress(argc,argv);            }        }).start();    }

3.运行结果

3.1Log输出

I/hwaps: JNI_OnLoadI/main: 当前帧：36I/main: 当前帧：48I/main: 当前帧：73I/main: 当前帧：85I/main: 当前帧：93I/main: 当前帧：99I/main: 当前帧：106I/main: 当前帧：113太多省略......

前言

1.引入FFmpeg命令行调用库

2.Android 核心代码

2.1.jni Java声明

2.2.核心代码ffmpeg_transcoding.c

调用ffmpeg_mod.c中ffmpegmain函数入口

2.3调用程序

3.运行结果

3.1Log输出

3.2转码输出

源码下载

Github：https://github.com/kpioneer123/FFmpegTest

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