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Gilles Boccon-Gibod
381
bumble/codecs.py
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381
bumble/codecs.py
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# Copyright 2023 Google LLC
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# -----------------------------------------------------------------------------
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# Imports
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# -----------------------------------------------------------------------------
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from __future__ import annotations
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from dataclasses import dataclass
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# -----------------------------------------------------------------------------
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class BitReader:
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"""Simple but not optimized bit stream reader."""
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data: bytes
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bytes_position: int
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bit_position: int
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cache: int
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bits_cached: int
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def __init__(self, data: bytes):
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self.data = data
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self.byte_position = 0
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self.bit_position = 0
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self.cache = 0
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self.bits_cached = 0
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def read(self, bits: int) -> int:
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""" "Read up to 32 bits."""
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if bits > 32:
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raise ValueError('maximum read size is 32')
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if self.bits_cached >= bits:
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# We have enough bits.
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self.bits_cached -= bits
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self.bit_position += bits
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return (self.cache >> self.bits_cached) & ((1 << bits) - 1)
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# Read more cache, up to 32 bits
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feed_bytes = self.data[self.byte_position : self.byte_position + 4]
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feed_size = len(feed_bytes)
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feed_int = int.from_bytes(feed_bytes, byteorder='big')
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if 8 * feed_size + self.bits_cached < bits:
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raise ValueError('trying to read past the data')
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self.byte_position += feed_size
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# Combine the new cache and the old cache
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cache = self.cache & ((1 << self.bits_cached) - 1)
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new_bits = bits - self.bits_cached
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self.bits_cached = 8 * feed_size - new_bits
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result = (feed_int >> self.bits_cached) | (cache << new_bits)
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self.cache = feed_int
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self.bit_position += bits
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return result
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def read_bytes(self, count: int):
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if self.bit_position + 8 * count > 8 * len(self.data):
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raise ValueError('not enough data')
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if self.bit_position % 8:
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# Not byte aligned
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result = bytearray(count)
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for i in range(count):
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result[i] = self.read(8)
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return bytes(result)
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# Byte aligned
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self.byte_position = self.bit_position // 8
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self.bits_cached = 0
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self.cache = 0
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offset = self.bit_position // 8
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self.bit_position += 8 * count
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return self.data[offset : offset + count]
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def bits_left(self) -> int:
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return (8 * len(self.data)) - self.bit_position
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def skip(self, bits: int) -> None:
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# Slow, but simple...
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while bits:
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if bits > 32:
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self.read(32)
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bits -= 32
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else:
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self.read(bits)
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break
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# -----------------------------------------------------------------------------
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class AacAudioRtpPacket:
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"""AAC payload encapsulated in an RTP packet payload"""
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@staticmethod
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def latm_value(reader: BitReader) -> int:
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bytes_for_value = reader.read(2)
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value = 0
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for _ in range(bytes_for_value + 1):
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value = value * 256 + reader.read(8)
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return value
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@staticmethod
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def program_config_element(reader: BitReader):
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raise ValueError('program_config_element not supported')
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@dataclass
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class GASpecificConfig:
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def __init__(
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self, reader: BitReader, channel_configuration: int, audio_object_type: int
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) -> None:
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# GASpecificConfig - ISO/EIC 14496-3 Table 4.1
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frame_length_flag = reader.read(1)
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depends_on_core_coder = reader.read(1)
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if depends_on_core_coder:
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self.core_coder_delay = reader.read(14)
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extension_flag = reader.read(1)
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if not channel_configuration:
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AacAudioRtpPacket.program_config_element(reader)
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if audio_object_type in (6, 20):
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self.layer_nr = reader.read(3)
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if extension_flag:
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if audio_object_type == 22:
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num_of_sub_frame = reader.read(5)
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layer_length = reader.read(11)
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if audio_object_type in (17, 19, 20, 23):
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aac_section_data_resilience_flags = reader.read(1)
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aac_scale_factor_data_resilience_flags = reader.read(1)
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aac_spectral_data_resilience_flags = reader.read(1)
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extension_flag_3 = reader.read(1)
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if extension_flag_3 == 1:
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raise ValueError('extensionFlag3 == 1 not supported')
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@staticmethod
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def audio_object_type(reader: BitReader):
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# GetAudioObjectType - ISO/EIC 14496-3 Table 1.16
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audio_object_type = reader.read(5)
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if audio_object_type == 31:
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audio_object_type = 32 + reader.read(6)
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return audio_object_type
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@dataclass
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class AudioSpecificConfig:
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audio_object_type: int
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sampling_frequency_index: int
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sampling_frequency: int
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channel_configuration: int
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sbr_present_flag: int
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ps_present_flag: int
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extension_audio_object_type: int
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extension_sampling_frequency_index: int
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extension_sampling_frequency: int
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extension_channel_configuration: int
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SAMPLING_FREQUENCIES = [
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96000,
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88200,
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64000,
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48000,
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44100,
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32000,
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24000,
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22050,
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16000,
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12000,
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11025,
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8000,
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7350,
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]
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def __init__(self, reader: BitReader) -> None:
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# AudioSpecificConfig - ISO/EIC 14496-3 Table 1.15
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self.audio_object_type = AacAudioRtpPacket.audio_object_type(reader)
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self.sampling_frequency_index = reader.read(4)
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if self.sampling_frequency_index == 0xF:
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self.sampling_frequency = reader.read(24)
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else:
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self.sampling_frequency = self.SAMPLING_FREQUENCIES[
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self.sampling_frequency_index
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]
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self.channel_configuration = reader.read(4)
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self.sbr_present_flag = -1
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self.ps_present_flag = -1
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if self.audio_object_type in (5, 29):
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self.extension_audio_object_type = 5
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self.sbc_present_flag = 1
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if self.audio_object_type == 29:
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self.ps_present_flag = 1
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self.extension_sampling_frequency_index = reader.read(4)
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if self.extension_sampling_frequency_index == 0xF:
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self.extension_sampling_frequency = reader.read(24)
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else:
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self.extension_sampling_frequency = self.SAMPLING_FREQUENCIES[
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self.extension_sampling_frequency_index
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]
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self.audio_object_type = AacAudioRtpPacket.audio_object_type(reader)
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if self.audio_object_type == 22:
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self.extension_channel_configuration = reader.read(4)
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else:
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self.extension_audio_object_type = 0
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if self.audio_object_type in (1, 2, 3, 4, 6, 7, 17, 19, 20, 21, 22, 23):
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ga_specific_config = AacAudioRtpPacket.GASpecificConfig(
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reader, self.channel_configuration, self.audio_object_type
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)
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else:
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raise ValueError(
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f'audioObjectType {self.audio_object_type} not supported'
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)
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# if self.extension_audio_object_type != 5 and bits_to_decode >= 16:
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# sync_extension_type = reader.read(11)
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# if sync_extension_type == 0x2B7:
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# self.extension_audio_object_type = AacAudioRtpPacket.audio_object_type(reader)
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# if self.extension_audio_object_type == 5:
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# self.sbr_present_flag = reader.read(1)
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# if self.sbr_present_flag:
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# self.extension_sampling_frequency_index = reader.read(4)
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# if self.extension_sampling_frequency_index == 0xF:
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# self.extension_sampling_frequency = reader.read(24)
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# else:
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# self.extension_sampling_frequency = self.SAMPLING_FREQUENCIES[self.extension_sampling_frequency_index]
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# if bits_to_decode >= 12:
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# sync_extension_type = reader.read(11)
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# if sync_extension_type == 0x548:
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# self.ps_present_flag = reader.read(1)
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# elif self.extension_audio_object_type == 22:
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# self.sbr_present_flag = reader.read(1)
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# if self.sbr_present_flag:
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# self.extension_sampling_frequency_index = reader.read(4)
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# if self.extension_sampling_frequency_index == 0xF:
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# self.extension_sampling_frequency = reader.read(24)
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# else:
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# self.extension_sampling_frequency = self.SAMPLING_FREQUENCIES[self.extension_sampling_frequency_index]
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# self.extension_channel_configuration = reader.read(4)
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@dataclass
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class StreamMuxConfig:
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other_data_present: int
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other_data_len_bits: int
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audio_specific_config: AacAudioRtpPacket.AudioSpecificConfig
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def __init__(self, reader: BitReader) -> None:
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# StreamMuxConfig - ISO/EIC 14496-3 Table 1.42
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audio_mux_version = reader.read(1)
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if audio_mux_version == 1:
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audio_mux_version_a = reader.read(1)
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else:
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audio_mux_version_a = 0
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if audio_mux_version_a != 0:
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raise ValueError('audioMuxVersionA != 0 not supported')
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if audio_mux_version == 1:
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tara_buffer_fullness = AacAudioRtpPacket.latm_value(reader)
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stream_cnt = 0
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all_streams_same_time_framing = reader.read(1)
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num_sub_frames = reader.read(6)
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num_program = reader.read(4)
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if num_program != 0:
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raise ValueError('num_program != 0 not supported')
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num_layer = reader.read(3)
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if num_layer != 0:
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raise ValueError('num_layer != 0 not supported')
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if audio_mux_version == 0:
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self.audio_specific_config = AacAudioRtpPacket.AudioSpecificConfig(
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reader
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)
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else:
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asc_len = AacAudioRtpPacket.latm_value(reader)
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marker = reader.bit_position
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self.audio_specific_config = AacAudioRtpPacket.AudioSpecificConfig(
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reader
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)
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audio_specific_config_len = reader.bit_position - marker
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if asc_len < audio_specific_config_len:
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raise ValueError('audio_specific_config_len > asc_len')
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asc_len -= audio_specific_config_len
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reader.skip(asc_len)
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frame_length_type = reader.read(3)
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if frame_length_type == 0:
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latm_buffer_fullness = reader.read(8)
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elif frame_length_type == 1:
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frame_length = reader.read(9)
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else:
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raise ValueError(f'frame_length_type {frame_length_type} not supported')
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self.other_data_present = reader.read(1)
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if self.other_data_present:
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if audio_mux_version == 1:
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self.other_data_len_bits = AacAudioRtpPacket.latm_value(reader)
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else:
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self.other_data_len_bits = 0
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while True:
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self.other_data_len_bits *= 256
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other_data_len_esc = reader.read(1)
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self.other_data_len_bits += reader.read(8)
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if other_data_len_esc == 0:
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break
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crc_check_present = reader.read(1)
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if crc_check_present:
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crc_checksum = reader.read(8)
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@dataclass
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class AudioMuxElement:
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payload: bytes
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stream_mux_config: AacAudioRtpPacket.StreamMuxConfig
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def __init__(self, reader: BitReader, mux_config_present: int):
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if mux_config_present == 0:
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raise ValueError('muxConfigPresent == 0 not supported')
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# AudioMuxElement - ISO/EIC 14496-3 Table 1.41
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use_same_stream_mux = reader.read(1)
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if use_same_stream_mux:
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raise ValueError('useSameStreamMux == 1 not supported')
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self.stream_mux_config = AacAudioRtpPacket.StreamMuxConfig(reader)
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# We only support:
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# allStreamsSameTimeFraming == 1
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# audioMuxVersionA == 0,
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# numProgram == 0
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# numSubFrames == 0
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# numLayer == 0
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mux_slot_length_bytes = 0
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while True:
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tmp = reader.read(8)
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mux_slot_length_bytes += tmp
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if tmp != 255:
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break
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self.payload = reader.read_bytes(mux_slot_length_bytes)
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if self.stream_mux_config.other_data_present:
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reader.skip(self.stream_mux_config.other_data_len_bits)
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# ByteAlign
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while reader.bit_position % 8:
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reader.read(1)
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def __init__(self, data: bytes) -> None:
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# Parse the bit stream
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reader = BitReader(data)
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self.audio_mux_element = self.AudioMuxElement(reader, mux_config_present=1)
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def to_adts(self):
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# pylint: disable=line-too-long
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sampling_frequency_index = (
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self.audio_mux_element.stream_mux_config.audio_specific_config.sampling_frequency_index
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)
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channel_configuration = (
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self.audio_mux_element.stream_mux_config.audio_specific_config.channel_configuration
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)
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frame_size = len(self.audio_mux_element.payload)
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return (
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bytes(
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[
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0xFF,
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0xF1, # 0xF9 (MPEG2)
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0x40
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| (sampling_frequency_index << 2)
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| (channel_configuration >> 2),
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((channel_configuration & 0x3) << 6) | ((frame_size + 7) >> 11),
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((frame_size + 7) >> 3) & 0xFF,
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(((frame_size + 7) << 5) & 0xFF) | 0x1F,
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0xFC,
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]
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)
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+ self.audio_mux_element.payload
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)
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