diff --git a/src/io/h264_writer/mod.rs b/src/io/h264_writer/mod.rs
index 1510d3f..ed7158f 100644
--- a/src/io/h264_writer/mod.rs
+++ b/src/io/h264_writer/mod.rs
@@ -65,9 +65,9 @@ impl<W: Write + Seek> Writer for H264Writer<W> {
         }
 
         if let Some(cached_packet) = &mut self.cached_packet {
-            cached_packet.depacketize(&packet.payload)?;
+            let payload = cached_packet.depacketize(&packet.payload)?;
 
-            self.writer.write_all(&cached_packet.payload)?;
+            self.writer.write_all(&payload)?;
         }
 
         Ok(())
diff --git a/src/io/ivf_writer/ivf_writer_test.rs b/src/io/ivf_writer/ivf_writer_test.rs
index 8751cbb..41c663c 100644
--- a/src/io/ivf_writer/ivf_writer_test.rs
+++ b/src/io/ivf_writer/ivf_writer_test.rs
@@ -87,33 +87,29 @@ fn test_ivf_writer_add_packet_and_close() -> Result<()> {
 
     // Check valid packet parameters
     let mut vp8packet = rtp::codecs::vp8::Vp8Packet::default();
-    vp8packet.depacketize(&valid_packet.payload)?;
+    let payload = vp8packet.depacketize(&valid_packet.payload)?;
     assert_eq!(1, vp8packet.s, "Start packet S value should be 1");
     assert_eq!(
         1,
-        vp8packet.payload[0] & 0x01,
+        payload[0] & 0x01,
         "Non Keyframe packet P value should be 1"
     );
 
     // Check mid partition packet parameters
     let mut vp8packet = rtp::codecs::vp8::Vp8Packet::default();
-    vp8packet.depacketize(&mid_part_packet.payload)?;
+    let payload = vp8packet.depacketize(&mid_part_packet.payload)?;
     assert_eq!(0, vp8packet.s, "Mid Partition packet S value should be 0");
     assert_eq!(
         1,
-        vp8packet.payload[0] & 0x01,
+        payload[0] & 0x01,
         "Non Keyframe packet P value should be 1"
     );
 
     // Check keyframe packet parameters
     let mut vp8packet = rtp::codecs::vp8::Vp8Packet::default();
-    vp8packet.depacketize(&keyframe_packet.payload)?;
+    let payload = vp8packet.depacketize(&keyframe_packet.payload)?;
     assert_eq!(1, vp8packet.s, "Start packet S value should be 1");
-    assert_eq!(
-        0,
-        vp8packet.payload[0] & 0x01,
-        "Keyframe packet P value should be 0"
-    );
+    assert_eq!(0, payload[0] & 0x01, "Keyframe packet P value should be 0");
 
     let add_packet_test_case = vec![
         (
@@ -170,7 +166,7 @@ fn test_ivf_writer_add_packet_and_close() -> Result<()> {
             assert!(result.is_ok(), "{}", msg1);
         }
 
-        assert_eq!(seen_key_frame, writer.seen_key_frame);
+        assert_eq!(seen_key_frame, writer.seen_key_frame, "{} failed", msg1);
         if count == 1 {
             assert_eq!(0, writer.count);
         } else if count == 2 {
diff --git a/src/io/ivf_writer/mod.rs b/src/io/ivf_writer/mod.rs
index c01ca29..da312a7 100644
--- a/src/io/ivf_writer/mod.rs
+++ b/src/io/ivf_writer/mod.rs
@@ -16,6 +16,7 @@ pub struct IVFWriter<W: Write + Seek> {
     count: u64,
     seen_key_frame: bool,
     current_frame: Option<BytesMut>,
+    is_vp9: bool,
 }
 
 impl<W: Write + Seek> IVFWriter<W> {
@@ -26,6 +27,7 @@ impl<W: Write + Seek> IVFWriter<W> {
             count: 0,
             seen_key_frame: false,
             current_frame: None,
+            is_vp9: &header.four_cc != b"VP80",
         };
 
         w.write_header(header)?;
@@ -54,24 +56,29 @@ impl<W: Write + Seek> IVFWriter<W> {
 impl<W: Write + Seek> Writer for IVFWriter<W> {
     /// write_rtp adds a new packet and writes the appropriate headers for it
     fn write_rtp(&mut self, packet: &rtp::packet::Packet) -> Result<()> {
-        let mut vp8packet = rtp::codecs::vp8::Vp8Packet::default();
-        vp8packet.depacketize(&packet.payload)?;
+        let mut depacketizer: Box<dyn Depacketizer> = if self.is_vp9 {
+            Box::new(rtp::codecs::vp9::Vp9Packet::default())
+        } else {
+            Box::new(rtp::codecs::vp8::Vp8Packet::default())
+        };
+
+        let payload = depacketizer.depacketize(&packet.payload)?;
 
-        let is_key_frame = vp8packet.payload[0] & 0x01;
+        let is_key_frame = payload[0] & 0x01;
 
         if (!self.seen_key_frame && is_key_frame == 1)
-            || (self.current_frame.is_none() && vp8packet.s != 1)
+            || (self.current_frame.is_none() && !depacketizer.is_partition_head(&packet.payload))
         {
             return Ok(());
         }
 
         self.seen_key_frame = true;
         let frame_length = if let Some(current_frame) = &mut self.current_frame {
-            current_frame.extend(vp8packet.payload);
+            current_frame.extend(payload);
             current_frame.len()
         } else {
             let mut current_frame = BytesMut::new();
-            current_frame.extend(vp8packet.payload);
+            current_frame.extend(payload);
             let frame_length = current_frame.len();
             self.current_frame = Some(current_frame);
             frame_length
diff --git a/src/io/ogg_writer/mod.rs b/src/io/ogg_writer/mod.rs
index 649718f..65b2659 100644
--- a/src/io/ogg_writer/mod.rs
+++ b/src/io/ogg_writer/mod.rs
@@ -159,7 +159,7 @@ impl<W: Write + Seek> Writer for OggWriter<W> {
     /// write_rtp adds a new packet and writes the appropriate headers for it
     fn write_rtp(&mut self, packet: &rtp::packet::Packet) -> Result<()> {
         let mut opus_packet = rtp::codecs::opus::OpusPacket::default();
-        opus_packet.depacketize(&packet.payload)?;
+        let payload = opus_packet.depacketize(&packet.payload)?;
 
         // Should be equivalent to sample_rate * duration
         if self.previous_timestamp != 1 {
@@ -169,7 +169,7 @@ impl<W: Write + Seek> Writer for OggWriter<W> {
         self.previous_timestamp = packet.header.timestamp;
 
         self.write_page(
-            &opus_packet.payload,
+            &payload,
             PAGE_HEADER_TYPE_CONTINUATION_OF_STREAM,
             self.previous_granule_position,
             self.page_index,