让FFMPEG支持实时流“伴随”转码

FFMPEG命令行工具目前无法针对视频实时流进行转码，而我们可以用它的新版本提供的支持TCP SERVER的特性来实现这一功能。实现边录边用FFMPEG提供的命令行工具进行转码。（实践证明，FFMPEG 的SDK针对实时流开发比较繁琐，命令行工具相对来说稳定）

我们将实时流录制成正在增长的文件，这样问题就变成了FFMPEG如何针对正在增长的视频文件转码。（首先我们保证视频格式是可以支持正在增长文件解码，这不在本文的讨论范畴）

而我们如果直接使用它对正在增长的文件转码，我们会发现FFMPEG转码到文件末尾（转码速度比录制速度快）就会退出。我们要做的就是在FFMPEG转码到末尾时如何将其挂起。若直接修改FFMPEG的源代码则比较繁琐，我们搭建一个TCP的FILE SERVER，来控制给FFMPEG发送数据的速度，而FFMPEG使用TCP的方式来获取视频流，即可实现这个功能。

以下是代码，我们用python来实现：

FFMPEG version:N-32611-gd55b06b

#encoding=utf8
'''
Created on 2011-9-25

@author: chenggong

ffmpeg扩展工具
'''
import SocketServer
import os
import threading
import time

BIN_DIR = "bin\"
BLOCK_SIZE = 188*1024
FRONTOFFSET = 1024 * 1024 * 1

gparam={'output':'','source':'','port':9333,
'start':0,'length':0,'ffmpeg_argvs':'',
'ffmpegsema':None,'tcpserversema':None}

class MyFfmpegThread(threading.Thread):
def run(self):
if os.path.exists(gparam['output']):
os.remove(gparam['output'])
argvs = gparam['ffmpeg_argvs'].replace("[filelocate]","tcp://127.0.0.1:%d"%gparam['port']) + " " + gparam['output']
cmd = "%s\avconv %s"%(BIN_DIR,argvs)
os.system(cmd)
gparam['ffmpegsema'].release()

class MyTcpServerThread(threading.Thread):
def run(self):
while True:
try:
ADDR = ("127.0.0.1", gparam['port'])
self.tcpServ = SocketServer.ThreadingTCPServer(ADDR, MyRequestHandler)
break
except Exception,e:
print str(e)
print "port:%d 被占用..更换"%gparam['port']
gparam['port']+=1
self.tcpServ.serve_forever()

def close(self):
self.tcpServ.shutdown()
self.tcpServ.server_close()

class MyRequestHandler(SocketServer.BaseRequestHandler):
def handle(self):
print 'connected from:', self.client_address
file = open(gparam['source'],"rb")

startoffset = gparam['start']
if startoffset<0:startoffset=0

print "start offset="+str(startoffset)
file.seek(startoffset)

left = gparam['length']
while(True):
try:
if(left<BLOCK_SIZE and left!=-1):
buffer_size = left
else:
buffer_size = BLOCK_SIZE
data=file.read(buffer_size)

#print "read data,size="+str(len(data))
#if(left!=-1): print "left size=%d"%left
if not data:
print "data empty! read to file_end,wait.."
finish_filename=gparam['source'].replace(os.path.splitext(gparam['source'])[1],".finish")
if(os.path.exists(finish_filename)):
print ".finish file founded"
break
time.sleep(1)
continue

self.request.sendall(data)

if(left!=-1):
left -= buffer_size
if(left<=0):
print "transfer finished"
break
if(len(data)<buffer_size):
finish_filename=gparam['source'].replace(os.path.splitext(gparam['source'])[1],".finish")
if(os.path.exists(finish_filename)):
print ".finish file founded"
break
else:
print "read to file_end,wait.."
time.sleep(1)
except:
print "exception occured,client stopped"
break
print "work finished"
file.close()
gparam['tcpserversema'].release()

def ffmpegex(source,output,start,length,ffmpeg_argvs):
gparam['source']=source
gparam['output']=output
gparam['start']=start
gparam['length']=length
gparam['ffmpeg_argvs']=ffmpeg_argvs

try:
while True:
gparam['ffmpegsema']=threading.Semaphore(0)
gparam['tcpserversema']=threading.Semaphore(0)
tcpServerThread = MyTcpServerThread()
tcpServerThread.start()
MyFfmpegThread().start()

gparam['ffmpegsema'].acquire()
gparam['tcpserversema'].acquire()
tcpServerThread.close()

filesize = os.path.getsize(gparam['output'])
if(filesize<length/10): #生成失败,将start提前，重做任务
if gparam['start']==0: return False
if gparam['start']-FRONTOFFSET>=0:
gparam['start']-=FRONTOFFSET
else:
gparam['start']=0
else:
return True
except:
return False

if __name__ == "__main__":

for i in range(0,100):
import random
start = random.randrange(0,1024*1024*1024)
print ffmpegex('C:\16942.ts','C:\test2\%d-%d.wmv'%(i,start),start,1024*1024*5,
"-i [filelocate] -acodec wmav2 -vcodec wmv2 -qscale 1 -ab 256k -r 25")

转自：http://blog.csdn.net/rcfalcon/article/details/6863119