diff --git a/src/main.rs b/src/main.rs
index d87da5a..b679290 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,16 +6,18 @@ use std::{
 };
 
 use rayon::ThreadPool;
+use thiserror::Error;
 
 use crate::controller::*;
 
 mod controller;
 
-fn main() 
+fn main() -> Result <(), TaskError>
 {
     let pool = rayon::ThreadPoolBuilder::new ().build ().unwrap ();
     let mut driver = Driver::new (&pool);
-    driver.main ();
+    driver.main ()?;
+    Ok (())
 }
 
 struct Driver <'a>
@@ -26,9 +28,9 @@ struct Driver <'a>
     
     ctl: Controller,
     
-    capture: Option <Capture>,
-    encoder: EncoderHandle,
-    transmitter: Option <Transmitter>,
+    capture: Task <Capture, ()>,
+    encoder: Task <Encoder, EncoderTaskMetadata>,
+    transmitter: Task <Transmitter, ()>,
 }
 
 impl <'a> Driver <'_>
@@ -45,13 +47,13 @@ impl <'a> Driver <'_>
             
             ctl: Default::default (),
             
-            capture: Some (Default::default ()),
-            encoder: EncoderHandle::Stopped (Default::default ()),
-            transmitter: Some (Default::default ()),
+            capture: Capture::default ().into (),
+            encoder: Encoder::default ().into (),
+            transmitter: Transmitter::default ().into (),
         }
     }
     
-    fn main (&mut self)
+    fn main (&mut self) -> Result <(), TaskError>
     {
         for _ in 0..10
         {
@@ -60,11 +62,11 @@ impl <'a> Driver <'_>
             if let Some (event) = ev.tx
             {
                 dbg! (&event);
-                self.handle_tx_event (event);
+                self.handle_tx_event (event)?;
                 
                 match self.recv.try_recv ()
                 {
-                    Ok (output) => self.handle_task_output (output),
+                    Ok (output) => self.handle_task_output (output)?,
                     Err (_) => (),
                 }
             }
@@ -72,52 +74,41 @@ impl <'a> Driver <'_>
             {
                 match self.recv.recv ()
                 {
-                    Ok (output) => self.handle_task_output (output),
+                    Ok (output) => self.handle_task_output (output)?,
                     Err (_) => (),
                 }
             }
         }
+        
+        Ok (())
     }
     
-    fn handle_task_output (&mut self, output: TaskOutput)
+    fn handle_task_output (&mut self, output: TaskOutput) -> Result <(), TaskError>
     {
         dbg! (&output);
         match output
         {
             TaskOutput::TxCapture ((cap, buf_raw)) =>
             {
-                let _old = match std::mem::replace (&mut self.capture, Some (cap))
-                {
-                    None => (),
-                    _ => panic! ("tried to finish an already finished capture"),
-                };
-                
+                self.capture.stop (cap)?;
                 self.ctl.handle_capture_frame (buf_raw).unwrap ();
             },
             TaskOutput::TxEncode (enc) =>
             {
-                let _metadata = match std::mem::replace (&mut self.encoder, EncoderHandle::Stopped (enc))
-                {
-                    EncoderHandle::Running (_) => (),
-                    _ => panic! ("tried to finish an already finished encode"),
-                };
-                
+                let _metadata = self.encoder.stop (enc)?;
                 self.ctl.handle_encoder_finished ();
             },
             TaskOutput::TxTransmit ((tx, busy)) =>
             {
-                let _old = match std::mem::replace (&mut self.transmitter, Some (tx))
-                {
-                    None => (),
-                    _ => panic! ("tried to finish an already finished transmit"),
-                };
-                
+                self.transmitter.stop (tx)?;
                 self.ctl.handle_network_busy (busy);
             }
         }
+        
+        Ok (())
     }
     
-    fn handle_tx_event (&mut self, event: TxPipelineEvent)
+    fn handle_tx_event (&mut self, event: TxPipelineEvent) -> Result <(), TaskError>
     {
         let dur_capture = Duration::from_millis (30);
         let dur_encode = Duration::from_millis (20);
@@ -128,14 +119,7 @@ impl <'a> Driver <'_>
         match event
         {
             TxPipelineEvent::Capture => {
-                let cap = match std::mem::replace (&mut self.capture, None)
-                {
-                    Some (x) => x,
-                    _ => {
-                        dbg! ("capture is already running");
-                        return;
-                    },
-                };
+                let cap = self.capture.start (())?;
                 
                 self.pool.spawn (move || 
                 {
@@ -149,11 +133,7 @@ impl <'a> Driver <'_>
             },
             TxPipelineEvent::PollEncoder =>
             {
-                let encoder = match &mut self.encoder
-                {
-                    EncoderHandle::Running (_) => panic! ("tried to poll encoder while it was running"),
-                    EncoderHandle::Stopped (x) => x,
-                };
+                let encoder = self.encoder.try_inner_mut ()?;
                 
                 let mut buf = vec! [];
                 
@@ -169,12 +149,7 @@ impl <'a> Driver <'_>
             }
             TxPipelineEvent::Encode (buf_raw) => 
             {
-                let metadata = EncoderTaskMetadata {};
-                let mut encoder = match std::mem::replace (&mut self.encoder, EncoderHandle::Running (metadata))
-                {
-                    EncoderHandle::Stopped (x) => x,
-                    _ => panic! ("tried to run the same encoder twice"),
-                };
+                let mut encoder = self.encoder.start (EncoderTaskMetadata {})?;
                 
                 self.pool.spawn (move || 
                 {
@@ -184,12 +159,7 @@ impl <'a> Driver <'_>
                 });
             },
             TxPipelineEvent::Transmit (_buf_enc) => {
-                let tx = match std::mem::replace (&mut self.transmitter, None)
-                {
-                    Some (x) => x,
-                    _ => panic! ("tried to run the same transmitter twice"),
-                };
-                
+                let tx = self.transmitter.start (())?;
                 self.pool.spawn (move ||
                 {
                     thread::sleep (dur_transmit);
@@ -197,13 +167,75 @@ impl <'a> Driver <'_>
                 });
             },
         }
+        
+        Ok (())
     }
 }
 
-enum EncoderHandle
+/// This is probably just a fancy Cell or something.
+
+enum Task <S, R>
 {
-    Stopped (Encoder),
-    Running (EncoderTaskMetadata),
+    Stopped (S),
+    Running (R),
+}
+
+#[derive (Debug, Error)]
+enum TaskError
+{
+    #[error ("tried to start already-running task")]
+    AlreadyRunning,
+    #[error ("tried to stop already-stopped task")]
+    AlreadyStopped,
+    #[error ("cannot access a task's inner object while it's running")]
+    CantAccessWhileRunning,
+}
+
+impl <S, R> From <S> for Task <S, R>
+{
+    fn from (x: S) -> Self
+    {
+        Self::Stopped (x)
+    }
+}
+
+impl <S, R> Task <S, R>
+{
+    fn try_inner (&self) -> Result <&S, TaskError>
+    {
+        match self
+        {
+            Self::Running (_) => Err (TaskError::CantAccessWhileRunning),
+            Self::Stopped (x) => Ok (x),
+        }
+    }
+    
+    fn try_inner_mut (&mut self) -> Result <&mut S, TaskError>
+    {
+        match self
+        {
+            Self::Running (_) => Err (TaskError::CantAccessWhileRunning),
+            Self::Stopped (x) => Ok (x),
+        }
+    }
+    
+    fn start (&mut self, x: R) -> Result <S, TaskError>
+    {
+        match std::mem::replace (self, Self::Running (x))
+        {
+            Self::Running (_) => Err (TaskError::AlreadyRunning),
+            Self::Stopped (x) => Ok (x),
+        }
+    }
+    
+    fn stop (&mut self, x: S) -> Result <R, TaskError>
+    {
+        match std::mem::replace (self, Self::Stopped (x))
+        {
+            Self::Stopped (_) => Err (TaskError::AlreadyStopped),
+            Self::Running (x) => Ok (x),
+        }
+    }
 }
 
 struct EncoderTaskMetadata