update readme

-/*
-The MIT License (MIT)
-
-Copyright (c) 2013 winlin
-
-Permission is hereby granted, free of charge, to any person obtaining a copy of
-this software and associated documentation files (the "Software"), to deal in
-the Software without restriction, including without limitation the rights to
-use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
-the Software, and to permit persons to whom the Software is furnished to do so,
-subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
-FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
-COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
-IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
-CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
-*/
-
-#include <srs_core_encoder.hpp>
-
-#include <stdlib.h>
-#include <unistd.h>
-
-#include <srs_core_error.hpp>
-#include <srs_core_log.hpp>
-#include <srs_core_config.hpp>
-
-#define SRS_ENCODER_SLEEP_MS 2000
-
-#define SRS_ENCODER_VCODEC "libx264"
-#define SRS_ENCODER_ACODEC "libaacplus"
-
-SrsFFMPEG::SrsFFMPEG(std::string ffmpeg_bin)
-{
-	started			= false;
-	pid				= -1;
-	ffmpeg 			= ffmpeg_bin;
-	
-	vbitrate 		= 0;
-	vfps 			= 0;
-	vwidth 			= 0;
-	vheight 		= 0;
-	vthreads 		= 0;
-	abitrate 		= 0;
-	asample_rate 	= 0;
-	achannels 		= 0;
-}
-
-SrsFFMPEG::~SrsFFMPEG()
-{
-	stop();
-}
-
-int SrsFFMPEG::initialize(std::string vhost, std::string port, std::string app, std::string stream, SrsConfDirective* engine)
-{
-	int ret = ERROR_SUCCESS;
-	
-	vcodec 			= config->get_engine_vcodec(engine);
-	vbitrate 		= config->get_engine_vbitrate(engine);
-	vfps 			= config->get_engine_vfps(engine);
-	vwidth 			= config->get_engine_vwidth(engine);
-	vheight 		= config->get_engine_vheight(engine);
-	vthreads 		= config->get_engine_vthreads(engine);
-	vprofile 		= config->get_engine_vprofile(engine);
-	vpreset 		= config->get_engine_vpreset(engine);
-	vparams 		= config->get_engine_vparams(engine);
-	acodec 			= config->get_engine_acodec(engine);
-	abitrate 		= config->get_engine_abitrate(engine);
-	asample_rate 	= config->get_engine_asample_rate(engine);
-	achannels 		= config->get_engine_achannels(engine);
-	aparams 		= config->get_engine_aparams(engine);
-	output 			= config->get_engine_output(engine);
-	
-	// ensure the size is even.
-	vwidth -= vwidth % 2;
-	vheight -= vheight % 2;
-
-	// input stream, from local.
-	// ie. rtmp://127.0.0.1:1935/live/livestream
-	input = "rtmp://127.0.0.1:";
-	input += port;
-	input += "/";
-	input += app;
-	input += "/";
-	input += stream;
-	
-	// output stream, to other/self server
-	// ie. rtmp://127.0.0.1:1935/live/livestream_sd
-	if (vhost == RTMP_VHOST_DEFAULT) {
-		output = srs_replace(output, "[vhost]", "127.0.0.1");
-	} else {
-		output = srs_replace(output, "[vhost]", vhost);
-	}
-	output = srs_replace(output, "[port]", port);
-	output = srs_replace(output, "[app]", app);
-	output = srs_replace(output, "[stream]", stream);
-
-	// important: loop check, donot transcode again.
-	// we think the following is loop circle:
-	// input: rtmp://127.0.0.1:1935/live/livestream_sd
-	// output: rtmp://127.0.0.1:1935/live/livestream_sd_sd
-	std::string tail = ""; // tail="_sd"
-	if (output.length() > input.length()) {
-		tail = output.substr(input.length());
-	}
-	// if input also endwiths the tail, loop detected.
-	if (!tail.empty() && input.rfind(tail) == input.length() - tail.length()) {
-		ret = ERROR_ENCODER_LOOP;
-		srs_info("detect a loop cycle, input=%s, output=%s, ignore it. ret=%d",
-			input.c_str(), output.c_str(), ret);
-		return ret;
-	}
-	
-	if (vcodec != SRS_ENCODER_VCODEC) {
-		ret = ERROR_ENCODER_VCODEC;
-		srs_error("invalid vcodec, must be %s, actual %s, ret=%d",
-			SRS_ENCODER_VCODEC, vcodec.c_str(), ret);
-		return ret;
-	}
-	if (vbitrate <= 0) {
-		ret = ERROR_ENCODER_VBITRATE;
-		srs_error("invalid vbitrate: %d, ret=%d", vbitrate, ret);
-		return ret;
-	}
-	if (vfps <= 0) {
-		ret = ERROR_ENCODER_VFPS;
-		srs_error("invalid vfps: %.2f, ret=%d", vfps, ret);
-		return ret;
-	}
-	if (vwidth <= 0) {
-		ret = ERROR_ENCODER_VWIDTH;
-		srs_error("invalid vwidth: %d, ret=%d", vwidth, ret);
-		return ret;
-	}
-	if (vheight <= 0) {
-		ret = ERROR_ENCODER_VHEIGHT;
-		srs_error("invalid vheight: %d, ret=%d", vheight, ret);
-		return ret;
-	}
-	if (vthreads < 0) {
-		ret = ERROR_ENCODER_VTHREADS;
-		srs_error("invalid vthreads: %d, ret=%d", vthreads, ret);
-		return ret;
-	}
-	if (vprofile.empty()) {
-		ret = ERROR_ENCODER_VPROFILE;
-		srs_error("invalid vprofile: %s, ret=%d", vprofile.c_str(), ret);
-		return ret;
-	}
-	if (vpreset.empty()) {
-		ret = ERROR_ENCODER_VPRESET;
-		srs_error("invalid vpreset: %s, ret=%d", vpreset.c_str(), ret);
-		return ret;
-	}
-	if (acodec != SRS_ENCODER_ACODEC) {
-		ret = ERROR_ENCODER_ACODEC;
-		srs_error("invalid acodec, must be %s, actual %s, ret=%d",
-			SRS_ENCODER_ACODEC, acodec.c_str(), ret);
-		return ret;
-	}
-	if (abitrate <= 0) {
-		ret = ERROR_ENCODER_ABITRATE;
-		srs_error("invalid abitrate: %d, ret=%d", 
-			abitrate, ret);
-		return ret;
-	}
-	if (asample_rate <= 0) {
-		ret = ERROR_ENCODER_ASAMPLE_RATE;
-		srs_error("invalid sample rate: %d, ret=%d", 
-			asample_rate, ret);
-		return ret;
-	}
-	if (achannels != 1 && achannels != 2) {
-		ret = ERROR_ENCODER_ACHANNELS;
-		srs_error("invalid achannels, must be 1 or 2, actual %d, ret=%d", 
-			achannels, ret);
-		return ret;
-	}
-	if (output.empty()) {
-		ret = ERROR_ENCODER_OUTPUT;
-		srs_error("invalid empty output, ret=%d", ret);
-		return ret;
-	}
-	
-	return ret;
-}
-
-int SrsFFMPEG::start()
-{
-	int ret = ERROR_SUCCESS;
-	
-	if (started) {
-		return ret;
-	}
-	
-	// prepare execl params
-	char vsize[22];
-	snprintf(vsize, sizeof(vsize), "%dx%d", vwidth, vheight);
-	char vaspect[22];
-	snprintf(vaspect, sizeof(vaspect), "%d:%d", vwidth, vheight);
-	char s_vbitrate[10];
-	snprintf(s_vbitrate, sizeof(s_vbitrate), "%d", vbitrate * 1000);
-	char s_vfps[10];
-	snprintf(s_vfps, sizeof(s_vfps), "%.2f", vfps);
-	char s_vthreads[10];
-	snprintf(s_vthreads, sizeof(s_vthreads), "%d", vthreads);
-	char s_abitrate[10];
-	snprintf(s_abitrate, sizeof(s_abitrate), "%d", abitrate * 1000);
-	char s_asample_rate[10];
-	snprintf(s_asample_rate, sizeof(s_asample_rate), "%d", asample_rate);
-	char s_achannels[10];
-	snprintf(s_achannels, sizeof(s_achannels), "%d", achannels);
-	
-	// TODO: execl donot support the params.
-	// video params
-	std::string s_vpreset = vpreset;
-	if (!vparams.empty()) {
-		s_vpreset += " ";
-		s_vpreset += vparams;
-	}
-	// audio params
-	std::string s_aparams = s_achannels;
-	if (!aparams.empty()) {
-		s_aparams += " ";
-		s_aparams += aparams;
-	}
-	
-	// TODO: fork or vfork?
-	if ((pid = fork()) < 0) {
-		ret = ERROR_ENCODER_FORK;
-		srs_error("vfork process failed. ret=%d", ret);
-		return ret;
-	}
-	
-	// child process: ffmpeg encoder engine.
-	if (pid == 0) {
-		// TODO: execl or execlp
-		ret = execl(ffmpeg.c_str(), 
-		    ffmpeg.c_str(),
-		    "-f", "flv",
-			"-i", input.c_str(), 
-			// video specified.
-			"-vcodec", vcodec.c_str(), 
-			"-b:v", s_vbitrate,
-			"-r", s_vfps,
-			"-s", vsize,
-			"-aspect", vaspect, // TODO: add aspect if needed.
-			"-threads", s_vthreads,
-			"-profile:v", vprofile.c_str(),
-			"-preset", s_vpreset.c_str(),
-			// audio specified.
-			"-acodec", acodec.c_str(),
-			"-b:a", s_abitrate,
-			"-ar", s_asample_rate,
-			"-ac", s_aparams.c_str(),
-			"-f", "flv",
-			"-y", output.c_str(),
-			NULL
-		);
-		if (ret < 0) {
-			fprintf(stderr, "fork ffmpeg failed, errno=%d(%s)", 
-				errno, strerror(errno));
-		}
-		exit(ret);
-	}
-
-	// parent.
-	if (pid > 0) {
-		started = true;
-		srs_trace("vfored ffmpeg encoder engine, pid=%d", pid);
-		return ret;
-	}
-	
-	return ret;
-}
-
-void SrsFFMPEG::stop()
-{
-	if (!started) {
-		return;
-	}
-}
-
-SrsEncoder::SrsEncoder()
-{
-	tid = NULL;
-	loop = false;
-}
-
-SrsEncoder::~SrsEncoder()
-{
-	on_unpublish();
-}
-
-int SrsEncoder::parse_scope_engines()
-{
-	int ret = ERROR_SUCCESS;
-	
-	// parse all transcode engines.
-	SrsConfDirective* conf = NULL;
-	
-	// parse vhost scope engines
-	std::string scope = "";
-	if ((conf = config->get_transcode(vhost, "")) != NULL) {
-		if ((ret = parse_transcode(conf)) != ERROR_SUCCESS) {
-			srs_error("parse vhost scope=%s transcode engines failed. "
-				"ret=%d", scope.c_str(), ret);
-			return ret;
-		}
-	}
-	// parse app scope engines
-	scope = app;
-	if ((conf = config->get_transcode(vhost, app)) != NULL) {
-		if ((ret = parse_transcode(conf)) != ERROR_SUCCESS) {
-			srs_error("parse app scope=%s transcode engines failed. "
-				"ret=%d", scope.c_str(), ret);
-			return ret;
-		}
-	}
-	// parse stream scope engines
-	scope += "/";
-	scope += stream;
-	if ((conf = config->get_transcode(vhost, app + "/" + stream)) != NULL) {
-		if ((ret = parse_transcode(conf)) != ERROR_SUCCESS) {
-			srs_error("parse stream scope=%s transcode engines failed. "
-				"ret=%d", scope.c_str(), ret);
-			return ret;
-		}
-	}
-	
-	return ret;
-}
-
-int SrsEncoder::on_publish(std::string _vhost, std::string _port, std::string _app, std::string _stream)
-{
-	int ret = ERROR_SUCCESS;
-
-	vhost = _vhost;
-	port = _port;
-	app = _app;
-	stream = _stream;
-
-	ret = parse_scope_engines();
-	
-	// ignore the loop encoder
-	if (ret = ERROR_ENCODER_LOOP) {
-		ret = ERROR_SUCCESS;
-	}
-	
-	// return for error or no engine.
-	if (ret != ERROR_SUCCESS || ffmpegs.empty()) {
-		return ret;
-	}
-    
-    // start thread to run all encoding engines.
-    srs_assert(!tid);
-    if((tid = st_thread_create(encoder_thread, this, 1, 0)) == NULL) {
-		ret = ERROR_ST_CREATE_FORWARD_THREAD;
-        srs_error("st_thread_create failed. ret=%d", ret);
-        return ret;
-    }
-    
-	return ret;
-}
-
-void SrsEncoder::on_unpublish()
-{
-	if (tid) {
-		loop = false;
-		st_thread_interrupt(tid);
-		st_thread_join(tid, NULL);
-		tid = NULL;
-	}
-
-	clear_engines();
-}
-
-void SrsEncoder::clear_engines()
-{
-	std::vector<SrsFFMPEG*>::iterator it;
-	for (it = ffmpegs.begin(); it != ffmpegs.end(); ++it) {
-		SrsFFMPEG* ffmpeg = *it;
-		srs_freep(ffmpeg);
-	}
-	ffmpegs.clear();
-}
-
-SrsFFMPEG* SrsEncoder::at(int index)
-{
-	return ffmpegs[index];
-}
-
-int SrsEncoder::parse_transcode(SrsConfDirective* conf)
-{
-	int ret = ERROR_SUCCESS;
-	
-	srs_assert(conf);
-	
-	// enabled
-	if (!config->get_transcode_enabled(conf)) {
-		srs_trace("ignore the disabled transcode: %s", 
-			conf->arg0().c_str());
-		return ret;
-	}
-	
-	// ffmpeg
-	std::string ffmpeg_bin = config->get_transcode_ffmpeg(conf);
-	if (ffmpeg_bin.empty()) {
-		srs_trace("ignore the empty ffmpeg transcode: %s", 
-			conf->arg0().c_str());
-		return ret;
-	}
-	
-	// get all engines.
-	std::vector<SrsConfDirective*> engines;
-	config->get_transcode_engines(conf, engines);
-	if (engines.empty()) {
-		srs_trace("ignore the empty transcode engine: %s", 
-			conf->arg0().c_str());
-		return ret;
-	}
-	
-	// create engine
-	for (int i = 0; i < (int)engines.size(); i++) {
-		SrsConfDirective* engine = engines[i];
-		if (!config->get_engine_enabled(engine)) {
-			srs_trace("ignore the diabled transcode engine: %s %s", 
-				conf->arg0().c_str(), engine->arg0().c_str());
-			continue;
-		}
-		
-		SrsFFMPEG* ffmpeg = new SrsFFMPEG(ffmpeg_bin);
-		
-		if ((ret = ffmpeg->initialize(vhost, port, app, stream, engine)) != ERROR_SUCCESS) {
-			srs_freep(ffmpeg);
-			
-			// if got a loop, donot transcode the whole stream.
-			if (ret == ERROR_ENCODER_LOOP) {
-				clear_engines();
-				break;
-			}
-			
-			srs_error("invalid transcode engine: %s %s", 
-				conf->arg0().c_str(), engine->arg0().c_str());
-			return ret;
-		}
-
-		ffmpegs.push_back(ffmpeg);
-	}
-	
-	return ret;
-}
-
-int SrsEncoder::cycle()
-{
-	int ret = ERROR_SUCCESS;
-	
-	// start all ffmpegs.
-	std::vector<SrsFFMPEG*>::iterator it;
-	for (it = ffmpegs.begin(); it != ffmpegs.end(); ++it) {
-		SrsFFMPEG* ffmpeg = *it;
-		if ((ret = ffmpeg->start()) != ERROR_SUCCESS) {
-			srs_error("ffmpeg start failed. ret=%d", ret);
-			return ret;
-		}
-	}
-	
-	return ret;
-}
-
-void SrsEncoder::encoder_cycle()
-{
-	int ret = ERROR_SUCCESS;
-	
-	log_context->generate_id();
-	srs_trace("encoder cycle start");
-	
-	while (loop) {
-		if ((ret = cycle()) != ERROR_SUCCESS) {
-			srs_warn("encoder cycle failed, ignored and retry, ret=%d", ret);
-		} else {
-			srs_info("encoder cycle success, retry");
-		}
-		
-		if (!loop) {
-			break;
-		}
-		
-		st_usleep(SRS_ENCODER_SLEEP_MS * 1000);
-	}
-	
-	// kill ffmpeg when finished and it alive
-	std::vector<SrsFFMPEG*>::iterator it;
-	for (it = ffmpegs.begin(); it != ffmpegs.end(); ++it) {
-		SrsFFMPEG* ffmpeg = *it;
-		ffmpeg->stop();
-	}
-	
-	srs_trace("encoder cycle finished");
-}
-
-void* SrsEncoder::encoder_thread(void* arg)
-{
-	SrsEncoder* obj = (SrsEncoder*)arg;
-	srs_assert(obj != NULL);
-	
-	obj->loop = true;
-	obj->encoder_cycle();
-	
-	return NULL;
-}
-
+/*
+The MIT License (MIT)
+
+Copyright (c) 2013 winlin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#include <srs_core_encoder.hpp>
+
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <srs_core_error.hpp>
+#include <srs_core_log.hpp>
+#include <srs_core_config.hpp>
+
+#define SRS_ENCODER_SLEEP_MS 2000
+
+#define SRS_ENCODER_VCODEC "libx264"
+#define SRS_ENCODER_ACODEC "libaacplus"
+
+SrsFFMPEG::SrsFFMPEG(std::string ffmpeg_bin)
+{
+	started			= false;
+	pid				= -1;
+	ffmpeg 			= ffmpeg_bin;
+	
+	vbitrate 		= 0;
+	vfps 			= 0;
+	vwidth 			= 0;
+	vheight 		= 0;
+	vthreads 		= 0;
+	abitrate 		= 0;
+	asample_rate 	= 0;
+	achannels 		= 0;
+}
+
+SrsFFMPEG::~SrsFFMPEG()
+{
+	stop();
+}
+
+int SrsFFMPEG::initialize(std::string vhost, std::string port, std::string app, std::string stream, SrsConfDirective* engine)
+{
+	int ret = ERROR_SUCCESS;
+	
+	vcodec 			= config->get_engine_vcodec(engine);
+	vbitrate 		= config->get_engine_vbitrate(engine);
+	vfps 			= config->get_engine_vfps(engine);
+	vwidth 			= config->get_engine_vwidth(engine);
+	vheight 		= config->get_engine_vheight(engine);
+	vthreads 		= config->get_engine_vthreads(engine);
+	vprofile 		= config->get_engine_vprofile(engine);
+	vpreset 		= config->get_engine_vpreset(engine);
+	vparams 		= config->get_engine_vparams(engine);
+	acodec 			= config->get_engine_acodec(engine);
+	abitrate 		= config->get_engine_abitrate(engine);
+	asample_rate 	= config->get_engine_asample_rate(engine);
+	achannels 		= config->get_engine_achannels(engine);
+	aparams 		= config->get_engine_aparams(engine);
+	output 			= config->get_engine_output(engine);
+	
+	// ensure the size is even.
+	vwidth -= vwidth % 2;
+	vheight -= vheight % 2;
+
+	// input stream, from local.
+	// ie. rtmp://127.0.0.1:1935/live/livestream
+	input = "rtmp://127.0.0.1:";
+	input += port;
+	input += "/";
+	input += app;
+	input += "/";
+	input += stream;
+	
+	// output stream, to other/self server
+	// ie. rtmp://127.0.0.1:1935/live/livestream_sd
+	if (vhost == RTMP_VHOST_DEFAULT) {
+		output = srs_replace(output, "[vhost]", "127.0.0.1");
+	} else {
+		output = srs_replace(output, "[vhost]", vhost);
+	}
+	output = srs_replace(output, "[port]", port);
+	output = srs_replace(output, "[app]", app);
+	output = srs_replace(output, "[stream]", stream);
+
+	// important: loop check, donot transcode again.
+	// we think the following is loop circle:
+	// input: rtmp://127.0.0.1:1935/live/livestream_sd
+	// output: rtmp://127.0.0.1:1935/live/livestream_sd_sd
+	std::string tail = ""; // tail="_sd"
+	if (output.length() > input.length()) {
+		tail = output.substr(input.length());
+	}
+	// if input also endwiths the tail, loop detected.
+	if (!tail.empty() && input.rfind(tail) == input.length() - tail.length()) {
+		ret = ERROR_ENCODER_LOOP;
+		srs_info("detect a loop cycle, input=%s, output=%s, ignore it. ret=%d",
+			input.c_str(), output.c_str(), ret);
+		return ret;
+	}
+	
+	if (vcodec != SRS_ENCODER_VCODEC) {
+		ret = ERROR_ENCODER_VCODEC;
+		srs_error("invalid vcodec, must be %s, actual %s, ret=%d",
+			SRS_ENCODER_VCODEC, vcodec.c_str(), ret);
+		return ret;
+	}
+	if (vbitrate <= 0) {
+		ret = ERROR_ENCODER_VBITRATE;
+		srs_error("invalid vbitrate: %d, ret=%d", vbitrate, ret);
+		return ret;
+	}
+	if (vfps <= 0) {
+		ret = ERROR_ENCODER_VFPS;
+		srs_error("invalid vfps: %.2f, ret=%d", vfps, ret);
+		return ret;
+	}
+	if (vwidth <= 0) {
+		ret = ERROR_ENCODER_VWIDTH;
+		srs_error("invalid vwidth: %d, ret=%d", vwidth, ret);
+		return ret;
+	}
+	if (vheight <= 0) {
+		ret = ERROR_ENCODER_VHEIGHT;
+		srs_error("invalid vheight: %d, ret=%d", vheight, ret);
+		return ret;
+	}
+	if (vthreads < 0) {
+		ret = ERROR_ENCODER_VTHREADS;
+		srs_error("invalid vthreads: %d, ret=%d", vthreads, ret);
+		return ret;
+	}
+	if (vprofile.empty()) {
+		ret = ERROR_ENCODER_VPROFILE;
+		srs_error("invalid vprofile: %s, ret=%d", vprofile.c_str(), ret);
+		return ret;
+	}
+	if (vpreset.empty()) {
+		ret = ERROR_ENCODER_VPRESET;
+		srs_error("invalid vpreset: %s, ret=%d", vpreset.c_str(), ret);
+		return ret;
+	}
+	if (acodec != SRS_ENCODER_ACODEC) {
+		ret = ERROR_ENCODER_ACODEC;
+		srs_error("invalid acodec, must be %s, actual %s, ret=%d",
+			SRS_ENCODER_ACODEC, acodec.c_str(), ret);
+		return ret;
+	}
+	if (abitrate <= 0) {
+		ret = ERROR_ENCODER_ABITRATE;
+		srs_error("invalid abitrate: %d, ret=%d", 
+			abitrate, ret);
+		return ret;
+	}
+	if (asample_rate <= 0) {
+		ret = ERROR_ENCODER_ASAMPLE_RATE;
+		srs_error("invalid sample rate: %d, ret=%d", 
+			asample_rate, ret);
+		return ret;
+	}
+	if (achannels != 1 && achannels != 2) {
+		ret = ERROR_ENCODER_ACHANNELS;
+		srs_error("invalid achannels, must be 1 or 2, actual %d, ret=%d", 
+			achannels, ret);
+		return ret;
+	}
+	if (output.empty()) {
+		ret = ERROR_ENCODER_OUTPUT;
+		srs_error("invalid empty output, ret=%d", ret);
+		return ret;
+	}
+	
+	return ret;
+}
+
+int SrsFFMPEG::start()
+{
+	int ret = ERROR_SUCCESS;
+	
+	if (started) {
+		return ret;
+	}
+	
+	// prepare execl params
+	char vsize[22];
+	snprintf(vsize, sizeof(vsize), "%dx%d", vwidth, vheight);
+	char vaspect[22];
+	snprintf(vaspect, sizeof(vaspect), "%d:%d", vwidth, vheight);
+	char s_vbitrate[10];
+	snprintf(s_vbitrate, sizeof(s_vbitrate), "%d", vbitrate * 1000);
+	char s_vfps[10];
+	snprintf(s_vfps, sizeof(s_vfps), "%.2f", vfps);
+	char s_vthreads[10];
+	snprintf(s_vthreads, sizeof(s_vthreads), "%d", vthreads);
+	char s_abitrate[10];
+	snprintf(s_abitrate, sizeof(s_abitrate), "%d", abitrate * 1000);
+	char s_asample_rate[10];
+	snprintf(s_asample_rate, sizeof(s_asample_rate), "%d", asample_rate);
+	char s_achannels[10];
+	snprintf(s_achannels, sizeof(s_achannels), "%d", achannels);
+	
+	// TODO: execl donot support the params.
+	// video params
+	std::string s_vpreset = vpreset;
+	if (!vparams.empty()) {
+		s_vpreset += " ";
+		s_vpreset += vparams;
+	}
+	// audio params
+	std::string s_aparams = s_achannels;
+	if (!aparams.empty()) {
+		s_aparams += " ";
+		s_aparams += aparams;
+	}
+	
+	// TODO: fork or vfork?
+	if ((pid = fork()) < 0) {
+		ret = ERROR_ENCODER_FORK;
+		srs_error("vfork process failed. ret=%d", ret);
+		return ret;
+	}
+	
+	// child process: ffmpeg encoder engine.
+	if (pid == 0) {
+		// TODO: execl or execlp 
+		ret = execl(ffmpeg.c_str(), 
+		    ffmpeg.c_str(),
+		    "-f", "flv",
+			"-i", input.c_str(), 
+			// video specified.
+			"-vcodec", vcodec.c_str(), 
+			"-b:v", s_vbitrate,
+			"-r", s_vfps,
+			"-s", vsize,
+			"-aspect", vaspect, // TODO: add aspect if needed.
+			"-threads", s_vthreads,
+			"-profile:v", vprofile.c_str(),
+			"-preset", s_vpreset.c_str(),
+			// audio specified.
+			"-acodec", acodec.c_str(),
+			"-b:a", s_abitrate,
+			"-ar", s_asample_rate,
+			"-ac", s_aparams.c_str(),
+			"-f", "flv",
+			"-y", output.c_str(),
+			NULL
+		);
+		if (ret < 0) {
+			fprintf(stderr, "fork ffmpeg failed, errno=%d(%s)", 
+				errno, strerror(errno));
+		}
+		exit(ret);
+	}
+
+	// parent.
+	if (pid > 0) {
+		started = true;
+		srs_trace("vfored ffmpeg encoder engine, pid=%d", pid);
+		return ret;
+	}
+	
+	return ret;
+}
+
+void SrsFFMPEG::stop()
+{
+	if (!started) {
+		return;
+	}
+}
+
+SrsEncoder::SrsEncoder()
+{
+	tid = NULL;
+	loop = false;
+}
+
+SrsEncoder::~SrsEncoder()
+{
+	on_unpublish();
+}
+
+int SrsEncoder::parse_scope_engines()
+{
+	int ret = ERROR_SUCCESS;
+	
+	// parse all transcode engines.
+	SrsConfDirective* conf = NULL;
+	
+	// parse vhost scope engines
+	std::string scope = "";
+	if ((conf = config->get_transcode(vhost, "")) != NULL) {
+		if ((ret = parse_transcode(conf)) != ERROR_SUCCESS) {
+			srs_error("parse vhost scope=%s transcode engines failed. "
+				"ret=%d", scope.c_str(), ret);
+			return ret;
+		}
+	}
+	// parse app scope engines
+	scope = app;
+	if ((conf = config->get_transcode(vhost, app)) != NULL) {
+		if ((ret = parse_transcode(conf)) != ERROR_SUCCESS) {
+			srs_error("parse app scope=%s transcode engines failed. "
+				"ret=%d", scope.c_str(), ret);
+			return ret;
+		}
+	}
+	// parse stream scope engines
+	scope += "/";
+	scope += stream;
+	if ((conf = config->get_transcode(vhost, app + "/" + stream)) != NULL) {
+		if ((ret = parse_transcode(conf)) != ERROR_SUCCESS) {
+			srs_error("parse stream scope=%s transcode engines failed. "
+				"ret=%d", scope.c_str(), ret);
+			return ret;
+		}
+	}
+	
+	return ret;
+}
+
+int SrsEncoder::on_publish(std::string _vhost, std::string _port, std::string _app, std::string _stream)
+{
+	int ret = ERROR_SUCCESS;
+
+	vhost = _vhost;
+	port = _port;
+	app = _app;
+	stream = _stream;
+
+	ret = parse_scope_engines();
+	
+	// ignore the loop encoder
+	if (ret = ERROR_ENCODER_LOOP) {
+		ret = ERROR_SUCCESS;
+	}
+	
+	// return for error or no engine.
+	if (ret != ERROR_SUCCESS || ffmpegs.empty()) {
+		return ret;
+	}
+    
+    // start thread to run all encoding engines.
+    srs_assert(!tid);
+    if((tid = st_thread_create(encoder_thread, this, 1, 0)) == NULL) {
+		ret = ERROR_ST_CREATE_FORWARD_THREAD;
+        srs_error("st_thread_create failed. ret=%d", ret);
+        return ret;
+    }
+    
+	return ret;
+}
+
+void SrsEncoder::on_unpublish()
+{
+	if (tid) {
+		loop = false;
+		st_thread_interrupt(tid);
+		st_thread_join(tid, NULL);
+		tid = NULL;
+	}
+
+	clear_engines();
+}
+
+void SrsEncoder::clear_engines()
+{
+	std::vector<SrsFFMPEG*>::iterator it;
+	for (it = ffmpegs.begin(); it != ffmpegs.end(); ++it) {
+		SrsFFMPEG* ffmpeg = *it;
+		srs_freep(ffmpeg);
+	}
+	ffmpegs.clear();
+}
+
+SrsFFMPEG* SrsEncoder::at(int index)
+{
+	return ffmpegs[index];
+}
+
+int SrsEncoder::parse_transcode(SrsConfDirective* conf)
+{
+	int ret = ERROR_SUCCESS;
+	
+	srs_assert(conf);
+	
+	// enabled
+	if (!config->get_transcode_enabled(conf)) {
+		srs_trace("ignore the disabled transcode: %s", 
+			conf->arg0().c_str());
+		return ret;
+	}
+	
+	// ffmpeg
+	std::string ffmpeg_bin = config->get_transcode_ffmpeg(conf);
+	if (ffmpeg_bin.empty()) {
+		srs_trace("ignore the empty ffmpeg transcode: %s", 
+			conf->arg0().c_str());
+		return ret;
+	}
+	
+	// get all engines.
+	std::vector<SrsConfDirective*> engines;
+	config->get_transcode_engines(conf, engines);
+	if (engines.empty()) {
+		srs_trace("ignore the empty transcode engine: %s", 
+			conf->arg0().c_str());
+		return ret;
+	}
+	
+	// create engine
+	for (int i = 0; i < (int)engines.size(); i++) {
+		SrsConfDirective* engine = engines[i];
+		if (!config->get_engine_enabled(engine)) {
+			srs_trace("ignore the diabled transcode engine: %s %s", 
+				conf->arg0().c_str(), engine->arg0().c_str());
+			continue;
+		}
+		
+		SrsFFMPEG* ffmpeg = new SrsFFMPEG(ffmpeg_bin);
+		
+		if ((ret = ffmpeg->initialize(vhost, port, app, stream, engine)) != ERROR_SUCCESS) {
+			srs_freep(ffmpeg);
+			
+			// if got a loop, donot transcode the whole stream.
+			if (ret == ERROR_ENCODER_LOOP) {
+				clear_engines();
+				break;
+			}
+			
+			srs_error("invalid transcode engine: %s %s", 
+				conf->arg0().c_str(), engine->arg0().c_str());
+			return ret;
+		}
+
+		ffmpegs.push_back(ffmpeg);
+	}
+	
+	return ret;
+}
+
+int SrsEncoder::cycle()
+{
+	int ret = ERROR_SUCCESS;
+	
+	// start all ffmpegs.
+	std::vector<SrsFFMPEG*>::iterator it;
+	for (it = ffmpegs.begin(); it != ffmpegs.end(); ++it) {
+		SrsFFMPEG* ffmpeg = *it;
+		if ((ret = ffmpeg->start()) != ERROR_SUCCESS) {
+			srs_error("ffmpeg start failed. ret=%d", ret);
+			return ret;
+		}
+	}
+	
+	return ret;
+}
+
+void SrsEncoder::encoder_cycle()
+{
+	int ret = ERROR_SUCCESS;
+	
+	log_context->generate_id();
+	srs_trace("encoder cycle start");
+	
+	while (loop) {
+		if ((ret = cycle()) != ERROR_SUCCESS) {
+			srs_warn("encoder cycle failed, ignored and retry, ret=%d", ret);
+		} else {
+			srs_info("encoder cycle success, retry");
+		}
+		
+		if (!loop) {
+			break;
+		}
+		
+		st_usleep(SRS_ENCODER_SLEEP_MS * 1000);
+	}
+	
+	// kill ffmpeg when finished and it alive
+	std::vector<SrsFFMPEG*>::iterator it;
+	for (it = ffmpegs.begin(); it != ffmpegs.end(); ++it) {
+		SrsFFMPEG* ffmpeg = *it;
+		ffmpeg->stop();
+	}
+	
+	srs_trace("encoder cycle finished");
+}
+
+void* SrsEncoder::encoder_thread(void* arg)
+{
+	SrsEncoder* obj = (SrsEncoder*)arg;
+	srs_assert(obj != NULL);
+	
+	obj->loop = true;
+	obj->encoder_cycle();
+	
+	return NULL;
+}
+