diff --git a/bumble/hci.py b/bumble/hci.py
index 0e85e3f..30ea1da 100644
--- a/bumble/hci.py
+++ b/bumble/hci.py
@@ -1721,6 +1721,15 @@ class CodecID(SpecableEnum):
     VENDOR_SPECIFIC = 0xFF
 
 
+# From Bluetooth Assigned Numbers, 2.10 PCM_Data_Format
+class PcmDataFormat(SpecableEnum):
+    NA = 0x00
+    ONES_COMPLEMENT = 0x01
+    TWOS_COMPLEMENT = 0x02
+    SIGN_MAGNITUDE = 0x03
+    UNSIGNED = 0x04
+
+
 @dataclasses.dataclass(frozen=True)
 class CodingFormat:
     codec_id: CodecID
@@ -1729,7 +1738,7 @@ class CodingFormat:
 
     @classmethod
     def parse_from_bytes(cls, data: bytes, offset: int) -> tuple[int, CodingFormat]:
-        (codec_id, company_id, vendor_specific_codec_id) = struct.unpack_from(
+        codec_id, company_id, vendor_specific_codec_id = struct.unpack_from(
             '<BHH', data, offset
         )
         return offset + 5, cls(
@@ -2063,7 +2072,7 @@ class HCI_Object:
                 )
                 continue
 
-            (field_name, field_type) = object_field
+            field_name, field_type = object_field
             result += HCI_Object.serialize_field(hci_object[field_name], field_type)
 
         return bytes(result)
@@ -3106,8 +3115,8 @@ class HCI_Enhanced_Setup_Synchronous_Connection_Command(HCI_AsyncCommand):
     output_coding_format: int = field(metadata=metadata(CodingFormat.parse_from_bytes))
     input_coded_data_size: int = field(metadata=metadata(2))
     output_coded_data_size: int = field(metadata=metadata(2))
-    input_pcm_data_format: int = field(metadata=metadata(1))
-    output_pcm_data_format: int = field(metadata=metadata(1))
+    input_pcm_data_format: int = field(metadata=PcmDataFormat.type_metadata(1))
+    output_pcm_data_format: int = field(metadata=PcmDataFormat.type_metadata(1))
     input_pcm_sample_payload_msb_position: int = field(metadata=metadata(1))
     output_pcm_sample_payload_msb_position: int = field(metadata=metadata(1))
     input_data_path: int = field(metadata=metadata(1))
@@ -3118,13 +3127,6 @@ class HCI_Enhanced_Setup_Synchronous_Connection_Command(HCI_AsyncCommand):
     packet_type: int = field(metadata=metadata(2))
     retransmission_effort: int = field(metadata=metadata(1))
 
-    class PcmDataFormat(SpecableEnum):
-        NA = 0x00
-        ONES_COMPLEMENT = 0x01
-        TWOS_COMPLEMENT = 0x02
-        SIGN_MAGNITUDE = 0x03
-        UNSIGNED = 0x04
-
     class DataPath(SpecableEnum):
         HCI = 0x00
         PCM = 0x01
@@ -3171,8 +3173,8 @@ class HCI_Enhanced_Accept_Synchronous_Connection_Request_Command(HCI_AsyncComman
     output_coding_format: int = field(metadata=metadata(CodingFormat.parse_from_bytes))
     input_coded_data_size: int = field(metadata=metadata(2))
     output_coded_data_size: int = field(metadata=metadata(2))
-    input_pcm_data_format: int = field(metadata=metadata(1))
-    output_pcm_data_format: int = field(metadata=metadata(1))
+    input_pcm_data_format: int = field(metadata=PcmDataFormat.type_metadata(1))
+    output_pcm_data_format: int = field(metadata=PcmDataFormat.type_metadata(1))
     input_pcm_sample_payload_msb_position: int = field(metadata=metadata(1))
     output_pcm_sample_payload_msb_position: int = field(metadata=metadata(1))
     input_data_path: int = field(metadata=metadata(1))
diff --git a/bumble/hfp.py b/bumble/hfp.py
index e22aa1b..df6cc3b 100644
--- a/bumble/hfp.py
+++ b/bumble/hfp.py
@@ -44,6 +44,7 @@ from bumble.hci import (
     CodecID,
     CodingFormat,
     HCI_Enhanced_Setup_Synchronous_Connection_Command,
+    PcmDataFormat,
 )
 
 # -----------------------------------------------------------------------------
@@ -1954,12 +1955,8 @@ class EscoParameters:
     output_coding_format: CodingFormat = CodingFormat(CodecID.LINEAR_PCM)
     input_coded_data_size: int = 16
     output_coded_data_size: int = 16
-    input_pcm_data_format: (
-        HCI_Enhanced_Setup_Synchronous_Connection_Command.PcmDataFormat
-    ) = HCI_Enhanced_Setup_Synchronous_Connection_Command.PcmDataFormat.TWOS_COMPLEMENT
-    output_pcm_data_format: (
-        HCI_Enhanced_Setup_Synchronous_Connection_Command.PcmDataFormat
-    ) = HCI_Enhanced_Setup_Synchronous_Connection_Command.PcmDataFormat.TWOS_COMPLEMENT
+    input_pcm_data_format: PcmDataFormat = PcmDataFormat.TWOS_COMPLEMENT
+    output_pcm_data_format: PcmDataFormat = PcmDataFormat.TWOS_COMPLEMENT
     input_pcm_sample_payload_msb_position: int = 0
     output_pcm_sample_payload_msb_position: int = 0
     input_data_path: HCI_Enhanced_Setup_Synchronous_Connection_Command.DataPath = (
diff --git a/bumble/transport/usb.py b/bumble/transport/usb.py
index 81e3750..b6e684f 100644
--- a/bumble/transport/usb.py
+++ b/bumble/transport/usb.py
@@ -58,6 +58,8 @@ USB_BT_HCI_CLASS_TUPLE = (
     USB_DEVICE_PROTOCOL_BLUETOOTH_PRIMARY_CONTROLLER,
 )
 
+MAX_SCO_PACKET_SIZE = 1024
+
 
 # -----------------------------------------------------------------------------
 def load_libusb():
@@ -227,7 +229,17 @@ class UsbPacketSink:
         self.bulk_out = bulk_out
         self.isochronous_out = isochronous_out
         self.bulk_or_control_out_transfer = device.getTransfer()
-        self.isochronous_out_transfer = device.getTransfer(iso_packets=1)
+        self.isochronous_out_transfer = (
+            device.getTransfer(
+                iso_packets=(
+                    MAX_SCO_PACKET_SIZE // isochronous_out.getMaxPacketSize()
+                    if isochronous_out.getMaxPacketSize()
+                    else 1
+                )
+            )
+            if isochronous_out is not None
+            else None
+        )
         self.out_transfer_ready = asyncio.Semaphore(1)
         self.packets: asyncio.Queue[bytes] = (
             asyncio.Queue()
@@ -298,17 +310,29 @@ class UsbPacketSink:
                     self.bulk_or_control_out_transfer.submit()
                     submitted = True
                 elif packet_type == hci.HCI_SYNCHRONOUS_DATA_PACKET:
-                    if self.isochronous_out is None:
+                    if self.isochronous_out_transfer is None:
                         logger.warning(
                             color('isochronous packets not supported', 'red')
                         )
                         self.out_transfer_ready.release()
                         continue
 
+                    # Setup a list of packet lengths, each up to the max packet size
+                    iso_max_packet_size = self.isochronous_out.getMaxPacketSize()
+                    iso_packet_count = (
+                        len(packet_payload) + iso_max_packet_size - 1
+                    ) // iso_max_packet_size
+                    iso_packet_lengths = [iso_max_packet_size] * (iso_packet_count - 1)
+                    iso_packet_lengths.append(
+                        len(packet_payload) - sum(iso_packet_lengths)
+                    )
+
+                    # Set up and submit the isochronous transfer
                     self.isochronous_out_transfer.setIsochronous(
                         self.isochronous_out.getAddress(),
                         packet_payload,
                         callback=self.transfer_callback,
+                        iso_transfer_length_list=iso_packet_lengths,
                     )
                     self.isochronous_out_transfer.submit()
                     submitted = True
@@ -340,6 +364,9 @@ class UsbPacketSink:
             self.bulk_or_control_out_transfer,
             self.isochronous_out_transfer,
         ):
+            if transfer is None:
+                continue
+
             if transfer.isSubmitted():
                 # Try to cancel the transfer, but that may fail because it may have
                 # already completed
@@ -352,6 +379,11 @@ class UsbPacketSink:
                 except usb1.USBError as error:
                     logger.debug(f'OUT transfer likely already completed ({error})')
 
+            try:
+                transfer.close()
+            except usb1.USBError as error:
+                logger.warning(f'failed to close transfer ({error})')
+
 
 READ_SIZE = 4096
 
@@ -585,7 +617,7 @@ class UsbTransport(Transport):
         sink.start()
 
         # Create a thread to process events
-        self.event_thread = threading.Thread(target=self.run)
+        self.event_thread = threading.Thread(target=self.run, daemon=True)
         self.event_thread.start()
 
     def run(self):
diff --git a/examples/run_hfp_handsfree.py b/examples/run_hfp_handsfree.py
index efce3a2..29ad55a 100644
--- a/examples/run_hfp_handsfree.py
+++ b/examples/run_hfp_handsfree.py
@@ -41,28 +41,27 @@ output_wav: wave.Wave_write | None = None
 def on_audio_packet(packet: hci.HCI_SynchronousDataPacket) -> None:
     if (
         packet.packet_status
-        == hci.HCI_SynchronousDataPacket.Status.CORRECTLY_RECEIVED_DATA
+        != hci.HCI_SynchronousDataPacket.Status.CORRECTLY_RECEIVED_DATA
     ):
-        if output_wav:
-            # Save the PCM audio to the output
-            output_wav.writeframes(packet.data)
-    else:
         print('!!! discarding packet with status ', packet.packet_status.name)
+        return
+
+    frame_count = len(packet.data) // 2
+    print(f">>> received {frame_count} PCM samples")
+
+    if output_wav:
+        # Save the PCM audio to the output
+        output_wav.writeframes(packet.data)
 
     if input_wav and hf_protocol:
-        # Send PCM audio from the input
-        frame_count = len(packet.data) // 2
-        while frame_count:
-            # NOTE: we use a fixed number of frames here, this should likely be adjusted
-            # based on the transport parameters (like the USB max packet size)
-            chunk_size = min(frame_count, 16)
-            if not (pcm_data := input_wav.readframes(chunk_size)):
-                return
-            frame_count -= chunk_size
-            hf_protocol.dlc.multiplexer.l2cap_channel.connection.device.host.send_sco_sdu(
-                connection_handle=packet.connection_handle,
-                sdu=pcm_data,
-            )
+        # Send PCM audio from the input, same amount as what was received
+        while not (pcm_data := input_wav.readframes(frame_count)):
+            input_wav.setpos(0)  # Loop
+        print(f">>> sending {frame_count} PCM samples")
+        hf_protocol.dlc.multiplexer.l2cap_channel.connection.device.host.send_sco_sdu(
+            connection_handle=packet.connection_handle,
+            sdu=pcm_data,
+        )
 
 
 # -----------------------------------------------------------------------------
@@ -123,6 +122,16 @@ def on_sco_request(
         print('!!! no supported command for SCO connection request')
         return
 
+    global output_wav
+    if output_wav:
+        output_wav.setnchannels(1)
+        output_wav.setsampwidth(2)
+        match protocol.active_codec:
+            case hfp.AudioCodec.CVSD:
+                output_wav.setframerate(8000)
+            case hfp.AudioCodec.MSBC:
+                output_wav.setframerate(16000)
+
     connection.on('sco_connection', on_sco_connection)
 
 
@@ -159,15 +168,6 @@ def on_ag_indicator(indicator):
 # -----------------------------------------------------------------------------
 def on_codec_negotiation(codec: hfp.AudioCodec):
     print(f'### Negotiated codec: {codec.name}')
-    global output_wav
-    if output_wav:
-        output_wav.setnchannels(1)
-        output_wav.setsampwidth(2)
-        match codec:
-            case hfp.AudioCodec.CVSD:
-                output_wav.setframerate(8000)
-            case hfp.AudioCodec.MSBC:
-                output_wav.setframerate(16000)
 
 
 # -----------------------------------------------------------------------------