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import struct
def convert_to_wav(audio_data: bytes, mime_type: str) -> bytes:
"""Generates a WAV file header for the given audio data and parameters.
Args:
audio_data: The raw audio data as a bytes object.
mime_type: Mime type of the audio data.
Returns:
A bytes object representing the WAV file header.
"""
parameters = parse_audio_mime_type(mime_type)
bits_per_sample = parameters["bits_per_sample"]
sample_rate = parameters["rate"]
num_channels = 1
data_size = len(audio_data)
bytes_per_sample = bits_per_sample // 8
block_align = num_channels * bytes_per_sample
byte_rate = sample_rate * block_align
chunk_size = 36 + data_size # 36 bytes for header fields before data chunk size
# http://soundfile.sapp.org/doc/WaveFormat/
header = struct.pack(
"<4sI4s4sIHHIIHH4sI",
b"RIFF", # ChunkID
chunk_size, # ChunkSize (total file size - 8 bytes)
b"WAVE", # Format
b"fmt ", # Subchunk1ID
16, # Subchunk1Size (16 for PCM)
1, # AudioFormat (1 for PCM)
num_channels, # NumChannels
sample_rate, # SampleRate
byte_rate, # ByteRate
block_align, # BlockAlign
bits_per_sample, # BitsPerSample
b"data", # Subchunk2ID
data_size # Subchunk2Size (size of audio data)
)
return header + audio_data
def parse_audio_mime_type(mime_type: str) -> dict[str, int | None]:
"""Parses bits per sample and rate from an audio MIME type string.
Assumes bits per sample is encoded like "L16" and rate as "rate=xxxxx".
Args:
mime_type: The audio MIME type string (e.g., "audio/L16;rate=24000").
Returns:
A dictionary with "bits_per_sample" and "rate" keys. Values will be
integers if found, otherwise None.
"""
bits_per_sample = 16
rate = 24000
# Extract rate from parameters
parts = mime_type.split(";")
for param in parts: # Skip the main type part
param = param.strip()
if param.lower().startswith("rate="):
try:
rate_str = param.split("=", 1)[1]
rate = int(rate_str)
except (ValueError, IndexError):
# Handle cases like "rate=" with no value or non-integer value
pass # Keep rate as default
elif param.startswith("audio/L"):
try:
bits_per_sample = int(param.split("L", 1)[1])
except (ValueError, IndexError):
pass # Keep bits_per_sample as default if conversion fails
return {"bits_per_sample": bits_per_sample, "rate": rate}
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