實現簡易的android 直播技術

Android 的直播，主要使用的是camera采集的數據推流到服務器上，在客戶端播放camera采集的數據。采用SurfaceView+ SurfaceTexture來顯示camera數據, SurfaceTexture在接收圖像流之后,可以進行二次處理，比如(加字體水印), 處理完畢后再送給另一個SurfaceView用於顯示. 
先說說，android端采集攝像頭數據，這個網上有很多的資料，可以百度下。這里可以在回調函數OnPreviewFrame(byte[] data,Camera cma)中獲取攝像頭數據data. 
關鍵是如何把data傳輸到服務器，要實現這個目標，我使用ffmpeg 來解決這個為題。在android 工程創建jni文件夾，使用jni調用。native函數如下: 

// 在OnPreviewFrame中調用 
public native void push(byte[] data); 
// 可以在OnSurfcaeChanged(）中調用. 在jni中初始化輸出路徑. 
public native int initPush(String outputurl,int width,int height); 
在jni 層的代碼如下:

static void ffmpeg_init() {

avcodec_register_all();

#if CONFIG_AVDEVICE 
avdevice_register_all();

#endif 
avfilter_register_all();

av_register_all();

avformat_network_init();

}

static int avinit(int width, int height){
/**編碼開始*/
int ret;
if(codec==NULL){


     yuv_width = width;
     yuv_height = height;
     y_length = width * height;
     uv_length = width * height / 4;
     LOGI("init start\n");

    codec = avcodec_find_encoder(AV_CODEC_ID_H264);
    if (!codec) {
        LOGI("Codec not found\n");
        return -1;
    }

    c = avcodec_alloc_context3(codec);
    if (!c) {
        LOGI("Could not allocate video codec context\n");
        return -1;
    }


    /* put sample parameters */
    c->bit_rate = 400000;
    /* resolution must be a multiple of two */
    c->width = width;
    c->height = height;
    /* frames per second */
    //c->time_base = (AVRational){1,5};
    c->time_base.den = 25;
    c->time_base.num = 1;
    /* emit one intra frame every ten frames
              * check frame pict_type before passing frame
         * to encoder, if frame->pict_type is AV_PICTURE_TYPE_I
     * then gop_size is ignored and the output of encoder
     * will always be I frame irrespective to gop_size
     */
     if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
            c->flags |= CODEC_FLAG_GLOBAL_HEADER;
    c->gop_size = 10;
    c->max_b_frames = 10;
    c->pix_fmt = AV_PIX_FMT_YUV420P;
    //av_opt_set(c->priv_data, "preset", "slow", 0);
    av_opt_set(c->priv_data, "preset", "superfast", 0);
    av_opt_set(c->priv_data, "tune", "zerolatency", 0);
    /* open it */
    if (avcodec_open2(c, codec, NULL) < 0) {
        LOGI("Could not open codec\n");
        return -1;
    }
    LOGI("init end 1\n");

     video_st = avformat_new_stream(ofmt_ctx, codec);
        if (video_st == NULL) {
            LOGI("video_st == NULL\n");
            return -1;
        }
        video_st->time_base.num = 1;
        video_st->time_base.den = 25;
        video_st->codec = c;

    return 0;
}
/**編碼結束*/

}

 JNIEXPORT jint JNICALL Java_com_example_directvideo_MainActivity_initPush
 (JNIEnv *env, jobject obj,jstring out ,jint width, jint height){


 int ret ;
 ffmpeg_init();
const char* str = //"rtmp://192.168.1.102:1935/myapp/test1";
        //"/storage/emulated/0/zsy.mp4";
        (*env)->GetStringUTFChars(env, out, 0);
    LOGI("%s %d %d ", str,width,height);
    //AVOutputFormat *ofmt = NULL;
            //AVFormatContext *ofmt_ctx = NULL;
            //Output
                avformat_alloc_output_context2(&ofmt_ctx, NULL, "flv", str); //RTMP
                //avformat_alloc_output_context2(&ofmt_ctx, NULL, "mpegts", output_str);//UDP
                if (!ofmt_ctx) {
                    LOGI( "Could not create output context\n");
                    ret = AVERROR_UNKNOWN;
                    goto end;
                }
                 ret = avinit(width, height);

                ofmt = ofmt_ctx->oformat;
                //Open output URL
                if (!(ofmt->flags & AVFMT_NOFILE)) {
                    ret = avio_open(&ofmt_ctx->pb, str, AVIO_FLAG_WRITE);
                    if (ret < 0) {
                        LOGI( "Could not open output URL '%s'", str);
                        goto end;
                    }
                }
                ret = avformat_write_header(ofmt_ctx, NULL);
                        if (ret < 0) {
                            LOGE( "Error occurred when opening output URL\n");
                            goto end;
                }
    (*env)->ReleaseStringUTFChars(env, out, str);
    if (ret < 0 && ret != AVERROR_EOF) {
        LOGI( "Error occurred.\n");
        return ret;
    }

        intited = 1;
return 0;
}

注意傳輸視頻流時，必須使用h264編碼器進行編碼。初始化成功后，便可使用push()來推送每一幀的camera數據到服務器上。
本人在ubuntu系統中，利用ngnix + rtmp搭建了簡易的流媒體服務器。
在pc機上，使用ffplay rtmp://192.168.1.102:1935/myapp/test1的命令來播放視屏.