diff --git a/CHANGELOG.md b/CHANGELOG.md
index ed4833f..c06becd 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -22,6 +22,8 @@
 *   BREAKING: `retina::client::PacketItem::SenderReport` has been replaced with
     `retina::client::PacketItem::Rtcp`, to expose full RTCP compound packets.
     Likewise `retina::codec::CodecItem`.
+*   BREAKING: `retina::codec::Parameters` is now `retina::codec::ParametersRef`,
+    which references parameters stored within the `Stream` to reduce copying.
 *   minimum Rust version is now 1.59.
 
 ## `v0.3.10` (2022-05-09)
diff --git a/examples/client/mp4.rs b/examples/client/mp4.rs
index b6f9067..27641dd 100644
--- a/examples/client/mp4.rs
+++ b/examples/client/mp4.rs
@@ -23,7 +23,7 @@ use futures::{Future, StreamExt};
 use log::{debug, info, warn};
 use retina::{
     client::{SetupOptions, Transport},
-    codec::{AudioParameters, CodecItem, Parameters, VideoParameters},
+    codec::{AudioParameters, CodecItem, ParametersRef, VideoParameters},
 };
 
 use std::num::NonZeroU32;
@@ -98,7 +98,7 @@ macro_rules! write_box {
 pub struct Mp4Writer<W: AsyncWrite + AsyncSeek + Send + Unpin> {
     mdat_start: u32,
     mdat_pos: u32,
-    video_params: Vec<Box<VideoParameters>>,
+    video_params: Vec<VideoParameters>,
 
     /// The most recently used 1-based index within `video_params`.
     cur_video_params_sample_description_index: Option<u32>,
@@ -548,13 +548,13 @@ impl<W: AsyncWrite + AsyncSeek + Send + Unpin> Mp4Writer<W> {
             i
         } else {
             match stream.parameters() {
-                Some(Parameters::Video(params)) => {
+                Some(ParametersRef::Video(params)) => {
                     log::info!("new video params: {:?}", params);
-                    let pos = self.video_params.iter().position(|p| **p == params);
+                    let pos = self.video_params.iter().position(|p| p == params);
                     if let Some(pos) = pos {
                         u32::try_from(pos + 1)?
                     } else {
-                        self.video_params.push(Box::new(params));
+                        self.video_params.push(params.clone());
                         u32::try_from(self.video_params.len())?
                     }
                 }
@@ -767,7 +767,7 @@ pub async fn run(opts: Opts) -> Result<(), Error> {
             .find_map(|(i, s)| match s.parameters() {
                 // Only consider audio streams that can produce a .mp4 sample
                 // entry.
-                Some(retina::codec::Parameters::Audio(a)) if a.sample_entry().is_some() => {
+                Some(retina::codec::ParametersRef::Audio(a)) if a.sample_entry().is_some() => {
                     log::info!("Using {} audio stream (rfc 6381 codec {})", s.encoding_name(), a.rfc6381_codec().unwrap());
                     Some((i, Box::new(a.clone())))
                 }
diff --git a/examples/client/onvif.rs b/examples/client/onvif.rs
index 4e716e8..2d49467 100644
--- a/examples/client/onvif.rs
+++ b/examples/client/onvif.rs
@@ -38,7 +38,12 @@ async fn run_inner(opts: Opts, session_group: Arc<SessionGroup>) -> Result<(), E
     let onvif_stream_i = session
         .streams()
         .iter()
-        .position(|s| matches!(s.parameters(), Some(retina::codec::Parameters::Message(..))))
+        .position(|s| {
+            matches!(
+                s.parameters(),
+                Some(retina::codec::ParametersRef::Message(..))
+            )
+        })
         .ok_or_else(|| anyhow!("couldn't find onvif stream"))?;
     session
         .setup(onvif_stream_i, SetupOptions::default())
diff --git a/src/client/mod.rs b/src/client/mod.rs
index 70dce99..6ce484c 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -814,7 +814,7 @@ impl Stream {
     /// When directly using [`Session`]'s packet-by-packet `futures::Stream` impl, codec
     /// depacketization logic is bypassed. The parameters returned by this function may be out of
     /// date.
-    pub fn parameters(&self) -> Option<crate::codec::Parameters> {
+    pub fn parameters(&self) -> Option<crate::codec::ParametersRef> {
         self.depacketizer.as_ref().ok().and_then(|d| d.parameters())
     }
 
diff --git a/src/client/parse.rs b/src/client/parse.rs
index 1633289..9373cd0 100644
--- a/src/client/parse.rs
+++ b/src/client/parse.rs
@@ -669,7 +669,7 @@ mod tests {
     use bytes::Bytes;
     use url::Url;
 
-    use crate::{client::StreamStateInit, codec::Parameters};
+    use crate::{client::StreamStateInit, codec::ParametersRef};
     use crate::{StreamContext, StreamContextInner, TcpStreamContext};
 
     use super::super::StreamState;
@@ -744,7 +744,7 @@ mod tests {
         assert_eq!(p.streams[0].rtp_payload_type, 96);
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.64001E");
                 assert_eq!(v.pixel_dimensions(), (704, 480));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -763,7 +763,7 @@ mod tests {
         assert_eq!(p.streams[1].rtp_payload_type, 97);
         assert_eq!(p.streams[1].clock_rate_hz, 48_000);
         match p.streams[1].parameters() {
-            Some(Parameters::Audio(_)) => {}
+            Some(ParametersRef::Audio(_)) => {}
             _ => panic!(),
         }
 
@@ -778,7 +778,7 @@ mod tests {
         assert_eq!(p.streams[2].clock_rate_hz, 90_000);
         assert!(matches!(
             p.streams[2].parameters(),
-            Some(Parameters::Message(_))
+            Some(ParametersRef::Message(_))
         ));
 
         // SETUP.
@@ -825,7 +825,7 @@ mod tests {
         assert_eq!(p.streams[1].encoding_name(), "pcma");
         assert_eq!(p.streams[1].rtp_payload_type, 8);
         match p.streams[1].parameters().unwrap() {
-            Parameters::Audio(_) => {}
+            ParametersRef::Audio(_) => {}
             _ => panic!(),
         };
     }
@@ -856,7 +856,7 @@ mod tests {
         assert_eq!(p.streams[0].rtp_payload_type, 96);
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.4D0029");
                 assert_eq!(v.pixel_dimensions(), (1920, 1080));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -876,7 +876,7 @@ mod tests {
         assert_eq!(p.streams[1].clock_rate_hz, 90_000);
         assert!(matches!(
             p.streams[1].parameters(),
-            Some(Parameters::Message(_))
+            Some(ParametersRef::Message(_))
         ));
 
         // SETUP.
@@ -936,7 +936,7 @@ mod tests {
         assert_eq!(p.streams[0].rtp_payload_type, 96);
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.640033");
                 assert_eq!(v.pixel_dimensions(), (2560, 1440));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -955,7 +955,7 @@ mod tests {
         assert_eq!(p.streams[1].rtp_payload_type, 97);
         assert_eq!(p.streams[1].clock_rate_hz, 16_000);
         match p.streams[1].parameters() {
-            Some(Parameters::Audio(_)) => {}
+            Some(ParametersRef::Audio(_)) => {}
             _ => panic!(),
         }
 
@@ -1019,7 +1019,7 @@ mod tests {
         assert_eq!(p.streams[0].clock_rate_hz, 12_000);
         assert_eq!(p.streams[0].channels, NonZeroU16::new(2));
         match p.streams[0].parameters() {
-            Some(Parameters::Audio(_)) => {}
+            Some(ParametersRef::Audio(_)) => {}
             _ => panic!(),
         }
 
@@ -1033,7 +1033,7 @@ mod tests {
         assert_eq!(p.streams[1].rtp_payload_type, 97);
         assert_eq!(p.streams[1].clock_rate_hz, 90_000);
         match p.streams[1].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.42C01E");
                 assert_eq!(v.pixel_dimensions(), (240, 160));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -1118,7 +1118,7 @@ mod tests {
         assert_eq!(p.streams[0].rtp_payload_type, 96);
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.4D001F");
                 assert_eq!(v.pixel_dimensions(), (1280, 720));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -1138,7 +1138,7 @@ mod tests {
         assert_eq!(p.streams[1].clock_rate_hz, 8_000);
         assert_eq!(p.streams[1].channels, NonZeroU16::new(1));
         match p.streams[1].parameters().unwrap() {
-            Parameters::Audio(_) => {}
+            ParametersRef::Audio(_) => {}
             _ => panic!(),
         };
     }
@@ -1165,7 +1165,7 @@ mod tests {
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
 
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.4D002A");
                 assert_eq!(v.pixel_dimensions(), (1920, 1080));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -1185,7 +1185,7 @@ mod tests {
         assert_eq!(p.streams[1].clock_rate_hz, 8_000);
         assert_eq!(p.streams[1].channels, NonZeroU16::new(1));
         match p.streams[1].parameters().unwrap() {
-            Parameters::Audio(_) => {}
+            ParametersRef::Audio(_) => {}
             _ => panic!(),
         };
     }
@@ -1211,7 +1211,7 @@ mod tests {
         assert_eq!(p.streams[0].rtp_payload_type, 96);
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.4D002A");
                 assert_eq!(v.pixel_dimensions(), (1920, 1080));
                 assert_eq!(v.pixel_aspect_ratio(), None);
@@ -1231,7 +1231,7 @@ mod tests {
         assert_eq!(p.streams[1].clock_rate_hz, 8_000);
         assert_eq!(p.streams[1].channels, NonZeroU16::new(1));
         match p.streams[1].parameters().unwrap() {
-            Parameters::Audio(_) => {}
+            ParametersRef::Audio(_) => {}
             _ => panic!(),
         };
 
@@ -1308,7 +1308,7 @@ mod tests {
         assert_eq!(p.streams[0].rtp_payload_type, 96);
         assert_eq!(p.streams[0].clock_rate_hz, 90_000);
         match p.streams[0].parameters().unwrap() {
-            Parameters::Video(v) => {
+            ParametersRef::Video(v) => {
                 assert_eq!(v.rfc6381_codec(), "avc1.4D001E");
                 assert_eq!(v.pixel_dimensions(), (720, 480));
                 assert_eq!(v.pixel_aspect_ratio(), None);
diff --git a/src/codec/aac.rs b/src/codec/aac.rs
index a6c8fcf..12c389e 100644
--- a/src/codec/aac.rs
+++ b/src/codec/aac.rs
@@ -23,7 +23,7 @@ use std::{
 
 use crate::{error::ErrorInt, rtp::ReceivedPacket, ConnectionContext, Error, StreamContext};
 
-use super::CodecItem;
+use super::{AudioParameters, CodecItem};
 
 /// An AudioSpecificConfig as in ISO/IEC 14496-3 section 1.6.2.1.
 ///
@@ -432,6 +432,7 @@ fn parse_format_specific_params(
 #[derive(Debug)]
 pub(crate) struct Depacketizer {
     config: AudioSpecificConfig,
+    parameters: AudioParameters,
     state: DepacketizerState,
 }
 
@@ -527,14 +528,16 @@ impl Depacketizer {
                 channels, config.channels
             ));
         }
+        let parameters = config.to_parameters();
         Ok(Self {
             config,
+            parameters,
             state: DepacketizerState::default(),
         })
     }
 
-    pub(super) fn parameters(&self) -> Option<super::Parameters> {
-        Some(super::Parameters::Audio(self.config.to_parameters()))
+    pub(super) fn parameters(&self) -> Option<super::ParametersRef> {
+        Some(super::ParametersRef::Audio(&self.parameters))
     }
 
     pub(super) fn push(&mut self, pkt: ReceivedPacket) -> Result<(), String> {
diff --git a/src/codec/g723.rs b/src/codec/g723.rs
index 9d1c6df..486c7bd 100644
--- a/src/codec/g723.rs
+++ b/src/codec/g723.rs
@@ -7,11 +7,14 @@ use std::num::NonZeroU32;
 
 use bytes::Bytes;
 
+use super::AudioParameters;
+
 const FIXED_CLOCK_RATE: u32 = 8_000;
 
 #[derive(Debug)]
 pub(crate) struct Depacketizer {
     pending: Option<super::AudioFrame>,
+    parameters: AudioParameters,
 }
 
 impl Depacketizer {
@@ -23,17 +26,20 @@ impl Depacketizer {
                 FIXED_CLOCK_RATE, clock_rate
             ));
         }
-        Ok(Self { pending: None })
+        Ok(Self {
+            pending: None,
+            parameters: AudioParameters {
+                rfc6381_codec: None,
+                frame_length: NonZeroU32::new(240),
+                clock_rate: FIXED_CLOCK_RATE,
+                extra_data: Bytes::new(),
+                sample_entry: None,
+            },
+        })
     }
 
-    pub(super) fn parameters(&self) -> Option<super::Parameters> {
-        Some(super::Parameters::Audio(super::AudioParameters {
-            rfc6381_codec: None,
-            frame_length: NonZeroU32::new(240),
-            clock_rate: FIXED_CLOCK_RATE,
-            extra_data: Bytes::new(),
-            sample_entry: None,
-        }))
+    pub(super) fn parameters(&self) -> Option<super::ParametersRef> {
+        Some(super::ParametersRef::Audio(&self.parameters))
     }
 
     fn validate(pkt: &crate::rtp::ReceivedPacket) -> bool {
diff --git a/src/codec/h264.rs b/src/codec/h264.rs
index c5af1ed..994ed7a 100644
--- a/src/codec/h264.rs
+++ b/src/codec/h264.rs
@@ -127,10 +127,10 @@ impl Depacketizer {
         })
     }
 
-    pub(super) fn parameters(&self) -> Option<super::Parameters> {
+    pub(super) fn parameters(&self) -> Option<super::ParametersRef> {
         self.parameters
             .as_ref()
-            .map(|p| super::Parameters::Video(p.generic_parameters.clone()))
+            .map(|p| super::ParametersRef::Video(&p.generic_parameters))
     }
 
     pub(super) fn push(&mut self, pkt: ReceivedPacket) -> Result<(), String> {
@@ -1360,7 +1360,7 @@ mod tests {
     fn depacketize_parameter_change() {
         let mut d = super::Depacketizer::new(90_000, Some("a=fmtp:96 profile-level-id=420029; packetization-mode=1; sprop-parameter-sets=Z01AHppkBYHv/lBgYGQAAA+gAAE4gBA=,aO48gA==")).unwrap();
         match d.parameters() {
-            Some(crate::codec::Parameters::Video(v)) => {
+            Some(crate::codec::ParametersRef::Video(v)) => {
                 assert_eq!(v.pixel_dimensions(), (704, 480));
             }
             _ => unreachable!(),
@@ -1426,7 +1426,7 @@ mod tests {
         // After pull, new_parameters and parameters() both reflect the change.
         assert!(frame.has_new_parameters);
         match d.parameters() {
-            Some(crate::codec::Parameters::Video(v)) => {
+            Some(crate::codec::ParametersRef::Video(v)) => {
                 assert_eq!(v.pixel_dimensions(), (640, 480));
             }
             _ => unreachable!(),
diff --git a/src/codec/mod.rs b/src/codec/mod.rs
index d33a3e6..9de37df 100644
--- a/src/codec/mod.rs
+++ b/src/codec/mod.rs
@@ -35,7 +35,7 @@ pub enum CodecItem {
     Rtcp(crate::rtcp::ReceivedCompoundPacket),
 }
 
-/// Parameters which describe a stream.
+/// Reference to parameters which describe a stream.
 ///
 /// Parameters are often, but not always, available immediately
 /// after `DESCRIBE` via [`crate::client::Stream::parameters`]. They should
@@ -47,10 +47,10 @@ pub enum CodecItem {
 ///
 /// Currently audio and message streams' parameters never change mid-stream.
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
-pub enum Parameters {
-    Video(VideoParameters),
-    Audio(AudioParameters),
-    Message(MessageParameters),
+pub enum ParametersRef<'a> {
+    Video(&'a VideoParameters),
+    Audio(&'a AudioParameters),
+    Message(&'a MessageParameters),
 }
 
 /// Parameters which describe a video stream.
@@ -514,7 +514,7 @@ impl Depacketizer {
     /// If the caller has called `push` more recently than `pull`, it's currently undefined
     /// whether the depacketizer returns parameters as of the most recently pulled or the upcoming
     /// frame.
-    pub fn parameters(&self) -> Option<Parameters> {
+    pub fn parameters(&self) -> Option<ParametersRef> {
         match &self.0 {
             DepacketizerInner::Aac(d) => d.parameters(),
             DepacketizerInner::G723(d) => d.parameters(),
@@ -595,7 +595,6 @@ mod tests {
                 "SenderReport",
                 std::mem::size_of::<crate::client::rtp::SenderReport>(),
             ),
-            ("Parameters", std::mem::size_of::<Parameters>()),
             ("VideoParameters", std::mem::size_of::<VideoParameters>()),
             ("AudioParameters", std::mem::size_of::<AudioParameters>()),
             (
diff --git a/src/codec/onvif.rs b/src/codec/onvif.rs
index b312dba..6e6a77f 100644
--- a/src/codec/onvif.rs
+++ b/src/codec/onvif.rs
@@ -10,7 +10,7 @@
 
 use bytes::{Buf, BufMut, BytesMut};
 
-use super::CodecItem;
+use super::{CodecItem, MessageParameters};
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum CompressionType {
@@ -22,7 +22,7 @@ pub enum CompressionType {
 
 #[derive(Debug)]
 pub(crate) struct Depacketizer {
-    compression_type: CompressionType,
+    parameters: MessageParameters,
     state: State,
     high_water_size: usize,
 }
@@ -45,16 +45,14 @@ struct InProgress {
 impl Depacketizer {
     pub(super) fn new(compression_type: CompressionType) -> Self {
         Depacketizer {
-            compression_type,
+            parameters: MessageParameters(compression_type),
             state: State::Idle,
             high_water_size: 0,
         }
     }
 
-    pub(super) fn parameters(&self) -> Option<super::Parameters> {
-        Some(super::Parameters::Message(super::MessageParameters(
-            self.compression_type,
-        )))
+    pub(super) fn parameters(&self) -> Option<super::ParametersRef> {
+        Some(super::ParametersRef::Message(&self.parameters))
     }
 
     pub(super) fn push(&mut self, pkt: crate::rtp::ReceivedPacket) -> Result<(), String> {
diff --git a/src/codec/simple_audio.rs b/src/codec/simple_audio.rs
index 74ac405..1be2c29 100644
--- a/src/codec/simple_audio.rs
+++ b/src/codec/simple_audio.rs
@@ -8,11 +8,11 @@ use std::num::NonZeroU32;
 
 use bytes::Bytes;
 
-use super::CodecItem;
+use super::{AudioParameters, CodecItem};
 
 #[derive(Debug)]
 pub(crate) struct Depacketizer {
-    clock_rate: u32,
+    parameters: AudioParameters,
     pending: Option<super::AudioFrame>,
     bits_per_sample: u32,
 }
@@ -21,20 +21,20 @@ impl Depacketizer {
     /// Creates a new Depacketizer.
     pub(super) fn new(clock_rate: u32, bits_per_sample: u32) -> Self {
         Self {
-            clock_rate,
+            parameters: AudioParameters {
+                rfc6381_codec: None,
+                frame_length: None, // variable
+                clock_rate,
+                extra_data: Bytes::new(),
+                sample_entry: None,
+            },
             bits_per_sample,
             pending: None,
         }
     }
 
-    pub(super) fn parameters(&self) -> Option<super::Parameters> {
-        Some(super::Parameters::Audio(super::AudioParameters {
-            rfc6381_codec: None,
-            frame_length: None, // variable
-            clock_rate: self.clock_rate,
-            extra_data: Bytes::new(),
-            sample_entry: None,
-        }))
+    pub(super) fn parameters(&self) -> Option<super::ParametersRef> {
+        Some(super::ParametersRef::Audio(&self.parameters))
     }
 
     fn frame_length(&self, payload_len: usize) -> Option<NonZeroU32> {