mirror of
https://github.com/liberatedsystems/openCom-Companion.git
synced 2024-11-21 21:10:36 +01:00
274 lines
8.8 KiB
Python
274 lines
8.8 KiB
Python
import ctypes
|
|
|
|
from . import opus
|
|
from .pyogg_error import PyOggError
|
|
|
|
class OpusDecoder:
|
|
def __init__(self):
|
|
self._decoder = None
|
|
self._channels = None
|
|
self._samples_per_second = None
|
|
self._pcm_buffer = None
|
|
self._pcm_buffer_ptr = None
|
|
self._pcm_buffer_size_int = None
|
|
|
|
# TODO: Check if there is clean up that we need to do when
|
|
# closing a decoder.
|
|
|
|
#
|
|
# User visible methods
|
|
#
|
|
|
|
def set_channels(self, n):
|
|
|
|
"""Set the number of channels.
|
|
|
|
n must be either 1 or 2.
|
|
|
|
The decoder is capable of filling in either mono or
|
|
interleaved stereo pcm buffers.
|
|
|
|
"""
|
|
if self._decoder is None:
|
|
if n < 0 or n > 2:
|
|
raise PyOggError(
|
|
"Invalid number of channels in call to "+
|
|
"set_channels()"
|
|
)
|
|
self._channels = n
|
|
else:
|
|
raise PyOggError(
|
|
"Cannot change the number of channels after "+
|
|
"the decoder was created. Perhaps "+
|
|
"set_channels() was called after decode()?"
|
|
)
|
|
self._create_pcm_buffer()
|
|
|
|
def set_sampling_frequency(self, samples_per_second):
|
|
"""Set the number of samples (per channel) per second.
|
|
|
|
samples_per_second must be one of 8000, 12000, 16000,
|
|
24000, or 48000.
|
|
|
|
Internally Opus stores data at 48000 Hz, so that should be
|
|
the default value for Fs. However, the decoder can
|
|
efficiently decode to buffers at 8, 12, 16, and 24 kHz so
|
|
if for some reason the caller cannot use data at the full
|
|
sample rate, or knows the compressed data doesn't use the
|
|
full frequency range, it can request decoding at a reduced
|
|
rate.
|
|
|
|
"""
|
|
if self._decoder is None:
|
|
if samples_per_second in [8000, 12000, 16000, 24000, 48000]:
|
|
self._samples_per_second = samples_per_second
|
|
else:
|
|
raise PyOggError(
|
|
"Specified sampling frequency "+
|
|
"({:d}) ".format(samples_per_second)+
|
|
"was not one of the accepted values"
|
|
)
|
|
else:
|
|
raise PyOggError(
|
|
"Cannot change the sampling frequency after "+
|
|
"the decoder was created. Perhaps "+
|
|
"set_sampling_frequency() was called after decode()?"
|
|
)
|
|
self._create_pcm_buffer()
|
|
|
|
def decode(self, encoded_bytes: memoryview):
|
|
"""Decodes an Opus-encoded packet into PCM.
|
|
|
|
"""
|
|
# If we haven't already created a decoder, do so now
|
|
if self._decoder is None:
|
|
self._decoder = self._create_decoder()
|
|
|
|
# Create a ctypes array from the memoryview (without copying
|
|
# data)
|
|
Buffer = ctypes.c_char * len(encoded_bytes)
|
|
encoded_bytes_ctypes = Buffer.from_buffer(encoded_bytes)
|
|
|
|
# Create pointer to encoded bytes
|
|
encoded_bytes_ptr = ctypes.cast(
|
|
encoded_bytes_ctypes,
|
|
ctypes.POINTER(ctypes.c_ubyte)
|
|
)
|
|
|
|
# Store length of encoded bytes into int32
|
|
len_int32 = opus.opus_int32(
|
|
len(encoded_bytes)
|
|
)
|
|
|
|
# Check that we have a PCM buffer
|
|
if self._pcm_buffer is None:
|
|
raise PyOggError("PCM buffer was not configured.")
|
|
|
|
# Decode the encoded frame
|
|
result = opus.opus_decode(
|
|
self._decoder,
|
|
encoded_bytes_ptr,
|
|
len_int32,
|
|
self._pcm_buffer_ptr,
|
|
self._pcm_buffer_size_int,
|
|
0 # TODO: What's Forward Error Correction about?
|
|
)
|
|
|
|
# Check for any errors
|
|
if result < 0:
|
|
raise PyOggError(
|
|
"An error occurred while decoding an Opus-encoded "+
|
|
"packet: "+
|
|
opus.opus_strerror(result).decode("utf")
|
|
)
|
|
|
|
# Extract just the valid data as bytes
|
|
end_valid_data = (
|
|
result
|
|
* ctypes.sizeof(opus.opus_int16)
|
|
* self._channels
|
|
)
|
|
|
|
# Create memoryview of PCM buffer to avoid copying data during slice.
|
|
mv = memoryview(self._pcm_buffer)
|
|
|
|
# Cast memoryview to chars
|
|
mv = mv.cast('c')
|
|
|
|
# Slice memoryview to extract only valid data
|
|
mv = mv[:end_valid_data]
|
|
|
|
return mv
|
|
|
|
|
|
def decode_missing_packet(self, frame_duration):
|
|
""" Obtain PCM data despite missing a frame.
|
|
|
|
frame_duration is in milliseconds.
|
|
|
|
"""
|
|
|
|
# Consider frame duration in units of 0.1ms in order to
|
|
# avoid floating-point comparisons.
|
|
if int(frame_duration*10) not in [25, 50, 100, 200, 400, 600]:
|
|
raise PyOggError(
|
|
"Frame duration ({:f}) is not one of the accepted values".format(frame_duration)
|
|
)
|
|
|
|
# Calculate frame size
|
|
frame_size = int(
|
|
frame_duration
|
|
* self._samples_per_second
|
|
// 1000
|
|
)
|
|
|
|
# Store frame size as int
|
|
frame_size_int = ctypes.c_int(frame_size)
|
|
|
|
# Decode missing packet
|
|
result = opus.opus_decode(
|
|
self._decoder,
|
|
None,
|
|
0,
|
|
self._pcm_buffer_ptr,
|
|
frame_size_int,
|
|
0 # TODO: What is this Forward Error Correction about?
|
|
)
|
|
|
|
# Check for any errors
|
|
if result < 0:
|
|
raise PyOggError(
|
|
"An error occurred while decoding an Opus-encoded "+
|
|
"packet: "+
|
|
opus.opus_strerror(result).decode("utf")
|
|
)
|
|
|
|
# Extract just the valid data as bytes
|
|
end_valid_data = (
|
|
result
|
|
* ctypes.sizeof(opus.opus_int16)
|
|
* self._channels
|
|
)
|
|
return bytes(self._pcm_buffer)[:end_valid_data]
|
|
|
|
#
|
|
# Internal methods
|
|
#
|
|
|
|
def _create_pcm_buffer(self):
|
|
if (self._samples_per_second is None
|
|
or self._channels is None):
|
|
# We cannot define the buffer yet
|
|
return
|
|
|
|
# Create buffer to hold 120ms of samples. See "opus_decode()" at
|
|
# https://opus-codec.org/docs/opus_api-1.3.1/group__opus__decoder.html
|
|
max_duration = 120 # milliseconds
|
|
max_samples = max_duration * self._samples_per_second // 1000
|
|
PCMBuffer = opus.opus_int16 * (max_samples * self._channels)
|
|
self._pcm_buffer = PCMBuffer()
|
|
self._pcm_buffer_ptr = (
|
|
ctypes.cast(ctypes.pointer(self._pcm_buffer),
|
|
ctypes.POINTER(opus.opus_int16))
|
|
)
|
|
|
|
# Store samples per channel in an int
|
|
self._pcm_buffer_size_int = ctypes.c_int(max_samples)
|
|
|
|
def _create_decoder(self):
|
|
# To create a decoder, we must first allocate resources for it.
|
|
# We want Python to be responsible for the memory deallocation,
|
|
# and thus Python must be responsible for the initial memory
|
|
# allocation.
|
|
|
|
# Check that the sampling frequency has been defined
|
|
if self._samples_per_second is None:
|
|
raise PyOggError(
|
|
"The sampling frequency was not specified before "+
|
|
"attempting to create an Opus decoder. Perhaps "+
|
|
"decode() was called before set_sampling_frequency()?"
|
|
)
|
|
|
|
# The sampling frequency must be passed in as a 32-bit int
|
|
samples_per_second = opus.opus_int32(self._samples_per_second)
|
|
|
|
# Check that the number of channels has been defined
|
|
if self._channels is None:
|
|
raise PyOggError(
|
|
"The number of channels were not specified before "+
|
|
"attempting to create an Opus decoder. Perhaps "+
|
|
"decode() was called before set_channels()?"
|
|
)
|
|
|
|
# The number of channels must also be passed in as a 32-bit int
|
|
channels = opus.opus_int32(self._channels)
|
|
|
|
# Obtain the number of bytes of memory required for the decoder
|
|
size = opus.opus_decoder_get_size(channels);
|
|
|
|
# Allocate the required memory for the decoder
|
|
memory = ctypes.create_string_buffer(size)
|
|
|
|
# Cast the newly-allocated memory as a pointer to a decoder. We
|
|
# could also have used opus.od_p as the pointer type, but writing
|
|
# it out in full may be clearer.
|
|
decoder = ctypes.cast(memory, ctypes.POINTER(opus.OpusDecoder))
|
|
|
|
# Initialise the decoder
|
|
error = opus.opus_decoder_init(
|
|
decoder,
|
|
samples_per_second,
|
|
channels
|
|
);
|
|
|
|
# Check that there hasn't been an error when initialising the
|
|
# decoder
|
|
if error != opus.OPUS_OK:
|
|
raise PyOggError(
|
|
"An error occurred while creating the decoder: "+
|
|
opus.opus_strerror(error).decode("utf")
|
|
)
|
|
|
|
# Return our newly-created decoder
|
|
return decoder
|