使用PJSUA2建立SIP呼叫时媒体会话创建失败（PJ_EBUSY）求助

我使用PJSUA2与某应用建立完整SIP呼叫，需执行流程：接听呼叫→播放消息→等待我方播放消息→回复播放另一消息后挂断。目前呼叫已连接至服务器（可查看呼叫ID及相关日志），但媒体会话无法创建，报错信息为Unable to create media session: Object is busy (PJ_EBUSY) [status=70011]。

相关日志流程：

• 我方发送INVITE请求
• 收到100 TRYING响应
• 收到200 OK响应
• SDP协商成功
• 呼叫进入CONNECTING状态
• 随即抛出上述媒体会话创建失败错误

以下是运行的Python 3.11代码：

import pjsua2 as pj
import time
import random

    
endpoint_config = pj.EpConfig()
endpoint_config.logConfig.level = 9
endpoint_config.medConfig.sndClockRate = 8000

endpoint = pj.Endpoint()

endpoint.libCreate()
endpoint.libInit(endpoint_config)
print("Endpoint initialized..")

# Create SIP transport
sip_transport_config = pj.TransportConfig()
transport_type = pj.PJSIP_TRANSPORT_TCP
sip_transport_config.port = 5060

endpoint.transportCreate(transport_type, sip_transport_config)
print("Transport created..")

# Start the library
endpoint.libStart()
print("Endpoint started..")

endpoint.libHandleEvents(10)

# Subclass to extend the Account and get notifications etc.
class MyAccount(pj.Account):
    def __init__(self):
        super().__init__()

    def onRegState(self, prm):
        ai = self.getInfo()
        print("*** Register: code=" if ai.regIsActive else "*** Unregister: code=", prm.code)

class MyCall(pj.Call):
    def __init__(self, account, call_id):
        super().__init__(account, call_id)
        self.acc = account
        self.connected = False

    def onCallState(self, prm):
        
        time.sleep(5)
        print(f"THE STATE OF THE CALL HAS CHANGED: {prm}")

        call_info = self.getInfo()
        self.connected = call_info.state == pj.PJSIP_INV_STATE_CONFIRMED

        print("CONNECTED:", self.connected)
        print("current state is " + str(call_info.state) + " " + call_info.stateText)
        print("GET ID:", self.getId())
        print("HAS MEDIA:", self.hasMedia())

    def onMediaState(self):
        
        print("ON MEDIA STATE")


# pjsua2 test function
def pj_test():
    account_config.idUri = "sip:111@111.111.1.1"

    account = MyAccount()
    try:
        account.create(account_config)
        print("ACCOUNT?", account)
        print("\nAccount created/registered..\n")

    except pj.Error as err:
        print("ERR acc:",err)

    call = MyCall(account, pj.PJSUA_INVALID_ID)
    

    prm = pj.CallOpParam(True)

    try:
        print("Attempting to make a call...")

        # USE prm.txOption – Optional headers etc to be added to outgoing INVITE request.
        call.makeCall("sip:+12011124111@sip.address:5060;transport=tcp", prm) ## Dev

        
        print("CALLINFO",callinfo := call.getInfo())
        print("STATE:", callinfo.state)
        print("CALLID:", callinfo.id)
        print("GET ID:", call.getId())
        print("HAS MEDIA:", call.hasMedia())

        
    except Exception as err:
        print("ERR:",err)
    # call.dump()

    endpoint.libDestroy()
if __name__ == "__main__":
    pj_test()

排查思路与解决方法 #

1. 检查资源占用冲突 #

PJ_EBUSY通常意味着媒体资源（音频设备、端口）被占用：

• 确认系统中无其他进程占用音频输入/输出设备（如浏览器、其他通话软件）；
• 用netstat -ano（Windows）或ss -tulpn（Linux）检查SDP协商的RTP端口及5060端口是否被占用。

2. 修复过早销毁Endpoint的问题 #

代码中调用call.makeCall()后立刻执行endpoint.libDestroy()，此时呼叫异步流程未完成，媒体资源被强制销毁导致冲突：

• 替换原有的endpoint.libDestroy()，添加事件循环监听呼叫状态，直到通话结束再销毁资源：

  # 替换原来的endpoint.libDestroy()
  while True:
      endpoint.libHandleEvents(10)
      call_info = call.getInfo()
      if call_info.state == pj.PJSIP_INV_STATE_DISCONNECTED:
          print("Call disconnected, exiting...")
          break
      time.sleep(0.1)
  endpoint.libDestroy()
  

3. 移除回调中的阻塞操作 #

onCallState里的time.sleep(5)会阻塞PJSUA2事件处理线程，导致媒体会话创建超时：

• 直接移除该睡眠语句，改用状态标记做后续异步处理。

4. 优化媒体配置 #

• 确认medConfig.sndClockRate与远端协商的媒体时钟速率一致，若远端用16000Hz，本地8000Hz可能导致初始化失败；
• 显式指定RTP端口范围避免冲突：

  endpoint_config.medConfig.rtpPortRange = pj.PjPortRange(5000, 5100)
  

5. 启用更详细的媒体日志 #

将日志级别调至10，重点查看pjmedia相关日志，定位具体被占用的资源：

endpoint_config.logConfig.level = 10

内容的提问来源于stack exchange，提问作者Barns89