Question

android 直播怎么实现的

Answer 1

android 的直播，主要使用的是camera采集的数据推流到服务器上，在客户端播放camera采集的数据。采用SurfaceView+ SurfaceTexture来显示camera数据, SurfaceTexture在接收图像流之后,可以进行二次处理，比如(加字体水印), 处理完毕后再送给另一个SurfaceView用于显示.
先说说，android端采集摄像头数据，这个网上有很多的资料，可以百度下。这里可以在回调函数OnPreviewFrame(byte[] data,Camera cma)中获取摄像头数据data.
关键是如何把data传输到服务器，要实现这个目标，我使用ffmpeg 来解决这个为题。在android 工程创建jni文件夹，使用jni调用。native函数如下:
// 在OnPreviewFrame中调用
public native void push(byte[] data);
// 可以在OnSurfcaeChanged(）中调用. 在jni中初始化输出路径.
public native int initPush(String outputurl,int width,int height);
在jni 层的代码如下:
static void ffmpeg_init() {
avcodec_register_all();
12

#if CONFIG_AVDEVICE
avdevice_register_all();
#endif
avfilter_register_all();
av_register_all();

avformat_network_init();
1234

}
static int avinit(int width, int height){
/**编码开始*/
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;
}
/**编码结束*/
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}
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;
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}
注意传输视频流时，必须使用h264编码器进行编码。初始化成功后，便可使用push()来推送每一帧的camera数据到服务器上。
本人在ubuntu系统中，利用ngnix + rtmp搭建了简易的流媒体服务器。
在pc机上，使用ffplay rtmp://192.168.1.102:1935/myapp/test1的命令来播放视屏.

http://blog.csdn.net/zsy2012919331/article/details/52444332