addTrack/inputFrame接口支持返回值；新增全局添加静音音频接口

src/Rtp/GB28181Process.cpp

@@ -149,6 +149,7 @@ bool GB28181Process::inputRtp(bool, const char *data, size_t data_len) {
         //设置frame回调
         _rtp_decoder[pt]->addDelegate(std::make_shared<FrameWriterInterfaceHelper>([this](const Frame::Ptr &frame) {
             onRtpDecode(frame);
+            return true;
         }));
     }