Android NDK開發(fā)之旅 目錄

前言

Windows下命令行轉碼壓縮形式

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

Android也是利用FFmpeg命令行的形式(混編)，進行視頻轉碼壓縮。

1.引入FFmpeg命令行調用庫

2.Android 核心代碼

2.1.jni Java聲明

    //視頻轉碼壓縮
    public native void transcodingCompress(int argc,String[] argv);

2.2.核心代碼ffmpeg_transcoding.c

#include "jni.h"
#include "ffmpeg.h"


//視頻轉碼壓縮主函數(shù)入口
//SDL（main）
//ffmpeg_mod.c有一個FFmpeg視頻轉碼主函數(shù)入口
//標記（聲明有一個這樣的函數(shù)提供給我調用）
//參數(shù)含義分析
//首先分析：String str = "ffmpeg -i input.mov -b:v 640k output.mp4"
// argc = str.split(" ").length()
// argv = str.split(" ")  字符串數(shù)組
//參數(shù)一：命令行字符串命令個數(shù)
//參數(shù)二：命令行字符串數(shù)組
int ffmpegmain(int argc, char **argv);


JNIEXPORT void JNICALL Java_com_haocai_ffmpegtest_util_VideoPlayer_transcodingCompress
        (JNIEnv *env, jobject jobj,jint jlen,jobjectArray jobjArray){
    //轉碼
    //將java的字符串數(shù)組轉成C字符串
    int argc = jlen;
    //開辟內存空間
    char **argv = (char**)malloc(sizeof(char*) * argc);

    //填充內容
    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);
    }

    //開始轉碼(底層實現(xiàn)就是只需命令)
    ffmpegmain(argc,argv);

    //釋放內存空間
    for (int i = 0; i < argc; ++i) {
        free(argv[i]);
    }

    //釋放數(shù)組
    free(argv);

}

調用ffmpeg_mod.c中ffmpegmain函數(shù)入口

//ffmpeg主函數(shù)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調用程序

   public void transcodingCompress(){

        final File inputFile;
        final File outputFile;
        final File dic = Environment.getExternalStorageDirectory();
        inputFile = new File(dic,"告白氣球.avi");
        outputFile = new File(dic,"告白氣球.mp4");

        new Thread(new Runnable() {
            @Override
            public void run() {
                //獲取視頻文件的路徑(sdcard路徑)
                // 拼接cmd 指令 ffmpeg -i 告白氣球.avi -b:v 640k 告白氣球.mp4 (與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 ");  //碼率越大 清晰度越高 碼率越小 清晰度越低
                builder.append(outputFile.getAbsolutePath());
                String[] argv = builder.toString().split(" ");
                int argc = argv.length;

                player.transcodingCompress(argc,argv);
            }
        }).start();

    }

3.運行結果

3.1Log輸出

I/hwaps: JNI_OnLoad
I/main: 當前幀：36
I/main: 當前幀：48
I/main: 當前幀：73
I/main: 當前幀：85
I/main: 當前幀：93
I/main: 當前幀：99
I/main: 當前幀：106
I/main: 當前幀：113
太多省略......

3.2轉碼輸出

源碼下載

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