wip

bumble/a2dp.py

@@ -17,12 +17,14 @@
 # -----------------------------------------------------------------------------
 from __future__ import annotations
 
-import dataclasses
-import struct
-import logging
 from collections.abc import AsyncGenerator
+import dataclasses
+import enum
+import logging
+import struct
 from typing import List, Callable, Awaitable
 
+from .codecs import AacAudioRtpPacket
 from .company_ids import COMPANY_IDENTIFIERS
 from .sdp import (
     DataElement,
@@ -535,6 +537,7 @@ class SbcFrame:
     block_count: int
     channel_mode: int
     subband_count: int
+    bitpool: int
     payload: bytes
 
     @property
@@ -555,6 +558,7 @@ class SbcFrame:
             f'cm={self.channel_mode},'
             f'br={self.bitrate},'
             f'sc={self.sample_count},'
+            f'bp={self.bitpool},'
             f'size={len(self.payload)})'
         )
 
@@ -602,7 +606,7 @@ class SbcParser:
 
                 # Emit the next frame
                 yield SbcFrame(
-                    sampling_frequency, blocks, channel_mode, subbands, payload
+                    sampling_frequency, blocks, channel_mode, subbands, bitpool, payload
                 )
 
         return generate_frames()
@@ -632,13 +636,12 @@ class SbcPacketSource:
             # NOTE: this doesn't support frame fragments
             sbc_parser = SbcParser(self.read)
             async for frame in sbc_parser.frames:
-                print(frame)
-
                 if (
                     frames_size + len(frame.payload) > max_rtp_payload
                     or len(frames) == 16
                 ):
                     # Need to flush what has been accumulated so far
+                    logger.debug(f"yielding {len(frames)} frames")
 
                     # Emit a packet
                     sbc_payload = bytes([len(frames)]) + b''.join(
@@ -663,3 +666,140 @@ class SbcPacketSource:
                     frames_size += len(frame.payload)
 
         return generate_packets()
+
+
+# -----------------------------------------------------------------------------
+@dataclasses.dataclass
+class AacFrame:
+    class Profile(enum.IntEnum):
+        MAIN = 0
+        LC = 1
+        SSR = 2
+        LTP = 3
+
+    profile: Profile
+    sampling_frequency: int
+    channel_configuration: int
+    payload: bytes
+
+    @property
+    def sample_count(self) -> int:
+        return 1024
+
+    @property
+    def duration(self) -> float:
+        return self.sample_count / self.sampling_frequency
+
+    def __str__(self) -> str:
+        return (
+            f'AAC(sf={self.sampling_frequency},'
+            f'ch={self.channel_configuration},'
+            f'size={len(self.payload)})'
+        )
+
+
+# -----------------------------------------------------------------------------
+ADTS_AAC_SAMPLING_FREQUENCIES = [
+    96000,
+    88200,
+    64000,
+    48000,
+    44100,
+    32000,
+    24000,
+    22050,
+    16000,
+    12000,
+    11025,
+    8000,
+    7350,
+    0,
+    0,
+    0,
+]
+
+
+# -----------------------------------------------------------------------------
+class AacParser:
+    """Parser for AAC frames in an ADTS stream"""
+
+    def __init__(self, read: Callable[[int], Awaitable[bytes]]) -> None:
+        self.read = read
+
+    @property
+    def frames(self) -> AsyncGenerator[AacFrame, None]:
+        async def generate_frames() -> AsyncGenerator[AacFrame, None]:
+            while True:
+                header = await self.read(7)
+                if not header:
+                    return
+
+                sync_word = (header[0] << 4) | (header[1] >> 4)
+                if sync_word != 0b111111111111:
+                    raise ValueError(f"invalid sync word ({sync_word:06x})")
+                layer = (header[1] >> 1) & 0b11
+                profile = AacFrame.Profile((header[2] >> 6) & 0b11)
+                sampling_frequency = ADTS_AAC_SAMPLING_FREQUENCIES[
+                    (header[2] >> 2) & 0b1111
+                ]
+                channel_configuration = ((header[2] & 0b1) << 2) | (header[3] >> 6)
+                frame_length = (
+                    ((header[3] & 0b11) << 11) | (header[4] << 3) | (header[5] >> 5)
+                )
+
+                if layer != 0:
+                    raise ValueError("layer must be 0")
+
+                payload = await self.read(frame_length - 7)
+                if payload:
+                    yield AacFrame(
+                        profile, sampling_frequency, channel_configuration, payload
+                    )
+
+        return generate_frames()
+
+
+# -----------------------------------------------------------------------------
+class AacPacketSource:
+    def __init__(
+        self, read: Callable[[int], Awaitable[bytes]], mtu: int, codec_capabilities
+    ) -> None:
+        self.read = read
+        self.mtu = mtu
+        self.codec_capabilities = codec_capabilities
+
+    @property
+    def packets(self):
+        async def generate_packets():
+            # pylint: disable=import-outside-toplevel
+            from .avdtp import MediaPacket  # Import here to avoid a circular reference
+
+            sequence_number = 0
+            timestamp = 0
+
+            aac_parser = AacParser(self.read)
+            async for frame in aac_parser.frames:
+                logger.debug("yielding one AAC frame")
+
+                # Emit a packet
+                aac_payload = bytes(
+                    AacAudioRtpPacket.for_simple_aac(
+                        frame.sampling_frequency,
+                        frame.channel_configuration,
+                        frame.payload,
+                    )
+                )
+                packet = MediaPacket(
+                    2, 0, 0, 0, sequence_number, timestamp, 0, [], 96, aac_payload
+                )
+                packet.timestamp_seconds = timestamp / frame.sampling_frequency
+                yield packet
+
+                # Prepare for next packets
+                sequence_number += 1
+                sequence_number &= 0xFFFF
+                timestamp += frame.sample_count
+                timestamp &= 0xFFFFFFFF
+                frames = [frame]
+
+        return generate_packets()

bumble/avc.py

@@ -119,7 +119,7 @@ class Frame:
             # Not supported
             raise NotImplementedError("extended subunit types not supported")
 
-        if subunit_id < 5:
+        if subunit_id < 5 or subunit_id == 7:
             opcode_offset = 2
         elif subunit_id == 5:
             # Extended to the next byte
@@ -132,7 +132,6 @@ class Frame:
             else:
                 subunit_id = 5 + extension
                 opcode_offset = 3
-
         elif subunit_id == 6:
             raise core.InvalidPacketError("reserved subunit ID")
 

bumble/avdtp.py

@@ -377,6 +377,7 @@ class MediaPacketPump:
         self.packets = packets
         self.clock = clock
         self.pump_task = None
+        self.completed = asyncio.Event()
 
     async def start(self, rtp_channel: l2cap.ClassicChannel) -> None:
         async def pump_packets():
@@ -406,6 +407,8 @@ class MediaPacketPump:
                     )
             except asyncio.exceptions.CancelledError:
                 logger.debug('pump canceled')
+            finally:
+                self.completed.set()
 
         # Pump packets
         self.pump_task = asyncio.create_task(pump_packets())
@@ -417,6 +420,9 @@ class MediaPacketPump:
             await self.pump_task
             self.pump_task = None
 
+    async def wait_for_completion(self) -> None:
+        await self.completed.wait()
+
 
 # -----------------------------------------------------------------------------
 class MessageAssembler:
@@ -1316,10 +1322,20 @@ class Protocol(EventEmitter):
         return None
 
     def add_source(
-        self, codec_capabilities: MediaCodecCapabilities, packet_pump: MediaPacketPump
+        self,
+        codec_capabilities: MediaCodecCapabilities,
+        packet_pump: MediaPacketPump,
+        delay_reporting: bool = False,
     ) -> LocalSource:
         seid = len(self.local_endpoints) + 1
-        source = LocalSource(self, seid, codec_capabilities, packet_pump)
+        service_capabilities = (
+            [ServiceCapabilities(AVDTP_DELAY_REPORTING_SERVICE_CATEGORY)]
+            if delay_reporting
+            else []
+        )
+        source = LocalSource(
+            self, seid, codec_capabilities, service_capabilities, packet_pump
+        )
         self.local_endpoints.append(source)
 
         return source
@@ -2180,12 +2196,13 @@ class LocalSource(LocalStreamEndPoint):
         protocol: Protocol,
         seid: int,
         codec_capabilities: MediaCodecCapabilities,
+        other_capabilitiles: Iterable[ServiceCapabilities],
         packet_pump: MediaPacketPump,
     ) -> None:
         capabilities = [
             ServiceCapabilities(AVDTP_MEDIA_TRANSPORT_SERVICE_CATEGORY),
             codec_capabilities,
-        ]
+        ] + list(other_capabilitiles)
         super().__init__(
             protocol,
             seid,

bumble/avrcp.py

@@ -1491,10 +1491,14 @@ class Protocol(pyee.EventEmitter):
             f"<<< AVCTP Command, transaction_label={transaction_label}: " f"{command}"
         )
 
-        # Only the PANEL subunit type with subunit ID 0 is supported in this profile.
-        if (
-            command.subunit_type != avc.Frame.SubunitType.PANEL
-            or command.subunit_id != 0
+        # Only addressing the unit, or the PANEL subunit with subunit ID 0 is supported
+        # in this profile.
+        if not (
+            command.subunit_type == avc.Frame.SubunitType.UNIT
+            and command.subunit_id == 7
+        ) and not (
+            command.subunit_type == avc.Frame.SubunitType.PANEL
+            and command.subunit_id == 0
         ):
             logger.debug("subunit not supported")
             self.send_not_implemented_response(transaction_label, command)
@@ -1528,8 +1532,8 @@ class Protocol(pyee.EventEmitter):
             # TODO: delegate
             response = avc.PassThroughResponseFrame(
                 avc.ResponseFrame.ResponseCode.ACCEPTED,
-                avc.Frame.SubunitType.PANEL,
-                0,
+                command.subunit_type,
+                command.subunit_id,
                 command.state_flag,
                 command.operation_id,
                 command.operation_data,
@@ -1846,6 +1850,15 @@ class Protocol(pyee.EventEmitter):
             RejectedResponse(pdu_id, status_code),
         )
 
+    def send_not_implemented_avrcp_response(
+        self, transaction_label: int, pdu_id: Protocol.PduId
+    ) -> None:
+        self.send_avrcp_response(
+            transaction_label,
+            avc.ResponseFrame.ResponseCode.NOT_IMPLEMENTED,
+            NotImplementedResponse(pdu_id, b''),
+        )
+
     def _on_get_capabilities_command(
         self, transaction_label: int, command: GetCapabilitiesCommand
     ) -> None:
@@ -1891,29 +1904,35 @@ class Protocol(pyee.EventEmitter):
         async def register_notification():
             # Check if the event is supported.
             supported_events = await self.delegate.get_supported_events()
-            if command.event_id in supported_events:
-                if command.event_id == EventId.VOLUME_CHANGED:
-                    volume = await self.delegate.get_absolute_volume()
-                    response = RegisterNotificationResponse(VolumeChangedEvent(volume))
-                    self.send_avrcp_response(
-                        transaction_label,
-                        avc.ResponseFrame.ResponseCode.INTERIM,
-                        response,
-                    )
-                    self._register_notification_listener(transaction_label, command)
-                    return
+            if command.event_id not in supported_events:
+                logger.debug("event not supported")
+                self.send_not_implemented_avrcp_response(
+                    transaction_label, self.PduId.REGISTER_NOTIFICATION
+                )
+                return
 
-                if command.event_id == EventId.PLAYBACK_STATUS_CHANGED:
-                    # TODO: testing only, use delegate
-                    response = RegisterNotificationResponse(
-                        PlaybackStatusChangedEvent(play_status=PlayStatus.PLAYING)
-                    )
-                    self.send_avrcp_response(
-                        transaction_label,
-                        avc.ResponseFrame.ResponseCode.INTERIM,
-                        response,
-                    )
-                    self._register_notification_listener(transaction_label, command)
-                    return
+            if command.event_id == EventId.VOLUME_CHANGED:
+                volume = await self.delegate.get_absolute_volume()
+                response = RegisterNotificationResponse(VolumeChangedEvent(volume))
+                self.send_avrcp_response(
+                    transaction_label,
+                    avc.ResponseFrame.ResponseCode.INTERIM,
+                    response,
+                )
+                self._register_notification_listener(transaction_label, command)
+                return
+
+            if command.event_id == EventId.PLAYBACK_STATUS_CHANGED:
+                # TODO: testing only, use delegate
+                response = RegisterNotificationResponse(
+                    PlaybackStatusChangedEvent(play_status=PlayStatus.PLAYING)
+                )
+                self.send_avrcp_response(
+                    transaction_label,
+                    avc.ResponseFrame.ResponseCode.INTERIM,
+                    response,
+                )
+                self._register_notification_listener(transaction_label, command)
+                return
 
         self._delegate_command(transaction_label, command, register_notification())

bumble/codecs.py

@@ -17,6 +17,7 @@
 # -----------------------------------------------------------------------------
 from __future__ import annotations
 from dataclasses import dataclass
+from typing_extensions import Self
 
 from bumble import core
 
@@ -101,12 +102,40 @@ class BitReader:
                 break
 
 
+# -----------------------------------------------------------------------------
+class BitWriter:
+    """Simple but not optimized bit stream writer."""
+
+    data: int
+    bit_count: int
+
+    def __init__(self) -> None:
+        self.data = 0
+        self.bit_count = 0
+
+    def write(self, value: int, bit_count: int) -> None:
+        self.data = (self.data << bit_count) | value
+        self.bit_count += bit_count
+
+    def write_bytes(self, data: bytes) -> None:
+        bit_count = 8 * len(data)
+        self.data = (self.data << bit_count) | int.from_bytes(data, 'big')
+        self.bit_count += bit_count
+
+    def __bytes__(self) -> bytes:
+        return (self.data << ((8 - (self.bit_count % 8)) % 8)).to_bytes(
+            (self.bit_count + 7) // 8, 'big'
+        )
+
+
 # -----------------------------------------------------------------------------
 class AacAudioRtpPacket:
     """AAC payload encapsulated in an RTP packet payload"""
 
+    audio_mux_element: AudioMuxElement
+
     @staticmethod
-    def latm_value(reader: BitReader) -> int:
+    def read_latm_value(reader: BitReader) -> int:
         bytes_for_value = reader.read(2)
         value = 0
         for _ in range(bytes_for_value + 1):
@@ -114,24 +143,33 @@ class AacAudioRtpPacket:
         return value
 
     @staticmethod
-    def program_config_element(reader: BitReader):
-        raise core.InvalidPacketError('program_config_element not supported')
+    def read_audio_object_type(reader: BitReader):
+        # GetAudioObjectType - ISO/EIC 14496-3 Table 1.16
+        audio_object_type = reader.read(5)
+        if audio_object_type == 31:
+            audio_object_type = 32 + reader.read(6)
+
+        return audio_object_type
 
     @dataclass
     class GASpecificConfig:
-        def __init__(
-            self, reader: BitReader, channel_configuration: int, audio_object_type: int
-        ) -> None:
+        audio_object_type: int
+        # NOTE: other fields not supported
+
+        @classmethod
+        def from_bits(
+            cls, reader: BitReader, channel_configuration: int, audio_object_type: int
+        ) -> Self:
             # GASpecificConfig - ISO/EIC 14496-3 Table 4.1
             frame_length_flag = reader.read(1)
             depends_on_core_coder = reader.read(1)
             if depends_on_core_coder:
-                self.core_coder_delay = reader.read(14)
+                core_coder_delay = reader.read(14)
             extension_flag = reader.read(1)
             if not channel_configuration:
-                AacAudioRtpPacket.program_config_element(reader)
+                raise core.InvalidPacketError('program_config_element not supported')
             if audio_object_type in (6, 20):
-                self.layer_nr = reader.read(3)
+                layer_nr = reader.read(3)
             if extension_flag:
                 if audio_object_type == 22:
                     num_of_sub_frame = reader.read(5)
@@ -144,14 +182,13 @@ class AacAudioRtpPacket:
                 if extension_flag_3 == 1:
                     raise core.InvalidPacketError('extensionFlag3 == 1 not supported')
 
-    @staticmethod
-    def audio_object_type(reader: BitReader):
-        # GetAudioObjectType - ISO/EIC 14496-3 Table 1.16
-        audio_object_type = reader.read(5)
-        if audio_object_type == 31:
-            audio_object_type = 32 + reader.read(6)
+            return cls(audio_object_type)
 
-        return audio_object_type
+        def to_bits(self, writer: BitWriter) -> None:
+            assert self.audio_object_type in (1, 2)
+            writer.write(0, 1)  # frame_length_flag = 0
+            writer.write(0, 1)  # depends_on_core_coder = 0
+            writer.write(0, 1)  # extension_flag = 0
 
     @dataclass
     class AudioSpecificConfig:
@@ -159,6 +196,7 @@ class AacAudioRtpPacket:
         sampling_frequency_index: int
         sampling_frequency: int
         channel_configuration: int
+        ga_specific_config: AacAudioRtpPacket.GASpecificConfig
         sbr_present_flag: int
         ps_present_flag: int
         extension_audio_object_type: int
@@ -182,44 +220,73 @@ class AacAudioRtpPacket:
             7350,
         ]
 
-        def __init__(self, reader: BitReader) -> None:
-            # AudioSpecificConfig - ISO/EIC 14496-3 Table 1.15
-            self.audio_object_type = AacAudioRtpPacket.audio_object_type(reader)
-            self.sampling_frequency_index = reader.read(4)
-            if self.sampling_frequency_index == 0xF:
-                self.sampling_frequency = reader.read(24)
-            else:
-                self.sampling_frequency = self.SAMPLING_FREQUENCIES[
-                    self.sampling_frequency_index
-                ]
-            self.channel_configuration = reader.read(4)
-            self.sbr_present_flag = -1
-            self.ps_present_flag = -1
-            if self.audio_object_type in (5, 29):
-                self.extension_audio_object_type = 5
-                self.sbc_present_flag = 1
-                if self.audio_object_type == 29:
-                    self.ps_present_flag = 1
-                self.extension_sampling_frequency_index = reader.read(4)
-                if self.extension_sampling_frequency_index == 0xF:
-                    self.extension_sampling_frequency = reader.read(24)
-                else:
-                    self.extension_sampling_frequency = self.SAMPLING_FREQUENCIES[
-                        self.extension_sampling_frequency_index
-                    ]
-                self.audio_object_type = AacAudioRtpPacket.audio_object_type(reader)
-                if self.audio_object_type == 22:
-                    self.extension_channel_configuration = reader.read(4)
-            else:
-                self.extension_audio_object_type = 0
+        @classmethod
+        def for_simple_aac(
+            cls,
+            audio_object_type: int,
+            sampling_frequency: int,
+            channel_configuration: int,
+        ) -> Self:
+            if sampling_frequency not in cls.SAMPLING_FREQUENCIES:
+                raise ValueError(f'invalid sampling frequency {sampling_frequency}')
 
-            if self.audio_object_type in (1, 2, 3, 4, 6, 7, 17, 19, 20, 21, 22, 23):
-                ga_specific_config = AacAudioRtpPacket.GASpecificConfig(
-                    reader, self.channel_configuration, self.audio_object_type
+            ga_specific_config = AacAudioRtpPacket.GASpecificConfig(audio_object_type)
+
+            return cls(
+                audio_object_type=audio_object_type,
+                sampling_frequency_index=cls.SAMPLING_FREQUENCIES.index(
+                    sampling_frequency
+                ),
+                sampling_frequency=sampling_frequency,
+                channel_configuration=channel_configuration,
+                ga_specific_config=ga_specific_config,
+                sbr_present_flag=0,
+                ps_present_flag=0,
+                extension_audio_object_type=0,
+                extension_sampling_frequency_index=0,
+                extension_sampling_frequency=0,
+                extension_channel_configuration=0,
+            )
+
+        @classmethod
+        def from_bits(cls, reader: BitReader) -> Self:
+            # AudioSpecificConfig - ISO/EIC 14496-3 Table 1.15
+            audio_object_type = AacAudioRtpPacket.read_audio_object_type(reader)
+            sampling_frequency_index = reader.read(4)
+            if sampling_frequency_index == 0xF:
+                sampling_frequency = reader.read(24)
+            else:
+                sampling_frequency = cls.SAMPLING_FREQUENCIES[sampling_frequency_index]
+            channel_configuration = reader.read(4)
+            sbr_present_flag = 0
+            ps_present_flag = 0
+            extension_sampling_frequency_index = 0
+            extension_sampling_frequency = 0
+            extension_channel_configuration = 0
+            extension_audio_object_type = 0
+            if audio_object_type in (5, 29):
+                extension_audio_object_type = 5
+                sbr_present_flag = 1
+                if audio_object_type == 29:
+                    ps_present_flag = 1
+                extension_sampling_frequency_index = reader.read(4)
+                if extension_sampling_frequency_index == 0xF:
+                    extension_sampling_frequency = reader.read(24)
+                else:
+                    extension_sampling_frequency = cls.SAMPLING_FREQUENCIES[
+                        extension_sampling_frequency_index
+                    ]
+                audio_object_type = AacAudioRtpPacket.read_audio_object_type(reader)
+                if audio_object_type == 22:
+                    extension_channel_configuration = reader.read(4)
+
+            if audio_object_type in (1, 2, 3, 4, 6, 7, 17, 19, 20, 21, 22, 23):
+                ga_specific_config = AacAudioRtpPacket.GASpecificConfig.from_bits(
+                    reader, channel_configuration, audio_object_type
                 )
             else:
                 raise core.InvalidPacketError(
-                    f'audioObjectType {self.audio_object_type} not supported'
+                    f'audioObjectType {audio_object_type} not supported'
                 )
 
             # if self.extension_audio_object_type != 5 and bits_to_decode >= 16:
@@ -248,13 +315,44 @@ class AacAudioRtpPacket:
             #                     self.extension_sampling_frequency = self.SAMPLING_FREQUENCIES[self.extension_sampling_frequency_index]
             #             self.extension_channel_configuration = reader.read(4)
 
+            return cls(
+                audio_object_type,
+                sampling_frequency_index,
+                sampling_frequency,
+                channel_configuration,
+                ga_specific_config,
+                sbr_present_flag,
+                ps_present_flag,
+                extension_audio_object_type,
+                extension_sampling_frequency_index,
+                extension_sampling_frequency,
+                extension_channel_configuration,
+            )
+
+        def to_bits(self, writer: BitWriter) -> None:
+            if self.sampling_frequency_index >= 15:
+                raise ValueError(
+                    f"unsupported sampling frequency index {self.sampling_frequency_index}"
+                )
+
+            if self.audio_object_type not in (1, 2):
+                raise ValueError(
+                    f"unsupported audio object type {self.audio_object_type} "
+                )
+
+            writer.write(self.audio_object_type, 5)
+            writer.write(self.sampling_frequency_index, 4)
+            writer.write(self.channel_configuration, 4)
+            self.ga_specific_config.to_bits(writer)
+
     @dataclass
     class StreamMuxConfig:
         other_data_present: int
         other_data_len_bits: int
         audio_specific_config: AacAudioRtpPacket.AudioSpecificConfig
 
-        def __init__(self, reader: BitReader) -> None:
+        @classmethod
+        def from_bits(cls, reader: BitReader) -> Self:
             # StreamMuxConfig - ISO/EIC 14496-3 Table 1.42
             audio_mux_version = reader.read(1)
             if audio_mux_version == 1:
@@ -264,7 +362,7 @@ class AacAudioRtpPacket:
             if audio_mux_version_a != 0:
                 raise core.InvalidPacketError('audioMuxVersionA != 0 not supported')
             if audio_mux_version == 1:
-                tara_buffer_fullness = AacAudioRtpPacket.latm_value(reader)
+                tara_buffer_fullness = AacAudioRtpPacket.read_latm_value(reader)
             stream_cnt = 0
             all_streams_same_time_framing = reader.read(1)
             num_sub_frames = reader.read(6)
@@ -275,13 +373,13 @@ class AacAudioRtpPacket:
             if num_layer != 0:
                 raise core.InvalidPacketError('num_layer != 0 not supported')
             if audio_mux_version == 0:
-                self.audio_specific_config = AacAudioRtpPacket.AudioSpecificConfig(
+                audio_specific_config = AacAudioRtpPacket.AudioSpecificConfig.from_bits(
                     reader
                 )
             else:
-                asc_len = AacAudioRtpPacket.latm_value(reader)
+                asc_len = AacAudioRtpPacket.read_latm_value(reader)
                 marker = reader.bit_position
-                self.audio_specific_config = AacAudioRtpPacket.AudioSpecificConfig(
+                audio_specific_config = AacAudioRtpPacket.AudioSpecificConfig.from_bits(
                     reader
                 )
                 audio_specific_config_len = reader.bit_position - marker
@@ -299,36 +397,49 @@ class AacAudioRtpPacket:
                     f'frame_length_type {frame_length_type} not supported'
                 )
 
-            self.other_data_present = reader.read(1)
-            if self.other_data_present:
+            other_data_present = reader.read(1)
+            other_data_len_bits = 0
+            if other_data_present:
                 if audio_mux_version == 1:
-                    self.other_data_len_bits = AacAudioRtpPacket.latm_value(reader)
+                    other_data_len_bits = AacAudioRtpPacket.read_latm_value(reader)
                 else:
-                    self.other_data_len_bits = 0
                     while True:
-                        self.other_data_len_bits *= 256
+                        other_data_len_bits *= 256
                         other_data_len_esc = reader.read(1)
-                        self.other_data_len_bits += reader.read(8)
+                        other_data_len_bits += reader.read(8)
                         if other_data_len_esc == 0:
                             break
             crc_check_present = reader.read(1)
             if crc_check_present:
                 crc_checksum = reader.read(8)
 
+            return cls(other_data_present, other_data_len_bits, audio_specific_config)
+
+        def to_bits(self, writer: BitWriter) -> None:
+            writer.write(0, 1)  # audioMuxVersion = 0
+            writer.write(1, 1)  # allStreamsSameTimeFraming = 1
+            writer.write(0, 6)  # numSubFrames = 0
+            writer.write(0, 4)  # numProgram = 0
+            writer.write(0, 3)  # numLayer = 0
+            self.audio_specific_config.to_bits(writer)
+            writer.write(0, 3)  # frameLengthType = 0
+            writer.write(0, 8)  # latmBufferFullness = 0
+            writer.write(0, 1)  # otherDataPresent = 0
+            writer.write(0, 1)  # crcCheckPresent = 0
+
     @dataclass
     class AudioMuxElement:
-        payload: bytes
         stream_mux_config: AacAudioRtpPacket.StreamMuxConfig
+        payload: bytes
 
-        def __init__(self, reader: BitReader, mux_config_present: int):
-            if mux_config_present == 0:
-                raise core.InvalidPacketError('muxConfigPresent == 0 not supported')
-
+        @classmethod
+        def from_bits(cls, reader: BitReader) -> Self:
             # AudioMuxElement - ISO/EIC 14496-3 Table 1.41
+            # (only supports mux_config_present=1)
             use_same_stream_mux = reader.read(1)
             if use_same_stream_mux:
                 raise core.InvalidPacketError('useSameStreamMux == 1 not supported')
-            self.stream_mux_config = AacAudioRtpPacket.StreamMuxConfig(reader)
+            stream_mux_config = AacAudioRtpPacket.StreamMuxConfig.from_bits(reader)
 
             # We only support:
             # allStreamsSameTimeFraming == 1
@@ -344,19 +455,46 @@ class AacAudioRtpPacket:
                 if tmp != 255:
                     break
 
-            self.payload = reader.read_bytes(mux_slot_length_bytes)
+            payload = reader.read_bytes(mux_slot_length_bytes)
 
-            if self.stream_mux_config.other_data_present:
-                reader.skip(self.stream_mux_config.other_data_len_bits)
+            if stream_mux_config.other_data_present:
+                reader.skip(stream_mux_config.other_data_len_bits)
 
             # ByteAlign
             while reader.bit_position % 8:
                 reader.read(1)
 
-    def __init__(self, data: bytes) -> None:
+            return cls(stream_mux_config, payload)
+
+        def to_bits(self, writer: BitWriter) -> None:
+            writer.write(0, 1)  # useSameStreamMux = 0
+            self.stream_mux_config.to_bits(writer)
+            mux_slot_length_bytes = len(self.payload)
+            while mux_slot_length_bytes > 255:
+                writer.write(255, 8)
+                mux_slot_length_bytes -= 255
+            writer.write(mux_slot_length_bytes, 8)
+            if mux_slot_length_bytes == 255:
+                writer.write(0, 8)
+            writer.write_bytes(self.payload)
+
+    @classmethod
+    def from_bytes(cls, data: bytes) -> Self:
         # Parse the bit stream
         reader = BitReader(data)
-        self.audio_mux_element = self.AudioMuxElement(reader, mux_config_present=1)
+        return cls(cls.AudioMuxElement.from_bits(reader))
+
+    @classmethod
+    def for_simple_aac(
+        cls, sampling_frequency: int, channel_configuration: int, payload: bytes
+    ) -> Self:
+        audio_specific_config = cls.AudioSpecificConfig.for_simple_aac(
+            2, sampling_frequency, channel_configuration
+        )
+        stream_mux_config = cls.StreamMuxConfig(0, 0, audio_specific_config)
+        audio_mux_element = cls.AudioMuxElement(stream_mux_config, payload)
+
+        return cls(audio_mux_element)
 
     def to_adts(self):
         # pylint: disable=line-too-long
@@ -383,3 +521,11 @@ class AacAudioRtpPacket:
             )
             + self.audio_mux_element.payload
         )
+
+    def __init__(self, audio_mux_element: AudioMuxElement) -> None:
+        self.audio_mux_element = audio_mux_element
+
+    def __bytes__(self) -> bytes:
+        writer = BitWriter()
+        self.audio_mux_element.to_bits(writer)
+        return bytes(writer)