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Simple HTTP FLAC streamer
from hashlib import md5
from audiotools.bitstream import BitstreamReader
from audiotools.flac import FlacAudio
from audiotools.flac import InvalidFLAC
from audiotools.id3 import skip_id3v2_comment
from audiotools.py_decoders import FlacDecoder
from audiotools.text import ERR_FLAC_INVALID_BLOCK
import requests
class StreamingFlacDecoder(FlacDecoder):
def __init__(self, url, channel_mask):
response = requests.get(url, stream=True)
self.reader = BitstreamReader(response.raw, 0)
if (self.reader.read_bytes(4) != 'fLaC'):
raise ValueError("invalid FLAC file")
self.current_md5sum = md5()
#locate the STREAMINFO,
#which is sometimes needed to handle non-subset streams
for (block_id,
block_size,
block_reader) in self.metadata_blocks(self.reader):
logger.info('Block info: %s, %d', block_id, block_size)
if (block_id == 0):
#read STREAMINFO
self.minimum_block_size = block_reader.read(16)
self.maximum_block_size = block_reader.read(16)
self.minimum_frame_size = block_reader.read(24)
self.maximum_frame_size = block_reader.read(24)
self.sample_rate = block_reader.read(20)
self.channels = block_reader.read(3) + 1
self.channel_mask = channel_mask
self.bits_per_sample = block_reader.read(5) + 1
self.total_frames = block_reader.read64(36)
self.md5sum = block_reader.read_bytes(16)
#these are frame header lookup tables
#which vary slightly depending on STREAMINFO's values
self.BLOCK_SIZE = [self.maximum_block_size,
192, 576, 1152,
2304, 4608, None, None,
256, 512, 1024, 2048,
4096, 8192, 16384, 32768]
self.SAMPLE_RATE = [self.sample_rate,
88200, 176400, 192000,
8000, 16000, 22050, 24000,
32000, 44100, 48000, 96000,
None, None, None, None]
self.BITS_PER_SAMPLE = [self.bits_per_sample,
8, 12, None, 16, 20, 24, None]
class StreamingFlacAudio(FlacAudio):
def __init__(self, url):
"""url is a plain string"""
FlacAudio.__init__(self, url)
# FIXME: use metadata from API
self.__channels__ = 2
self.__samplerate__ = 44100
def __read_streaminfo__(self):
pass
def to_pcm(self):
"""returns a PCMReader object containing the track's PCM data"""
from audiotools import PCMReaderError
try:
return StreamingFlacDecoder(self.filename,
self.channel_mask())
except (IOError, ValueError), msg:
#The only time this is likely to occur is
#if the FLAC is modified between when FlacAudio
#is initialized and when to_pcm() is called.
return PCMReaderError(error_message=str(msg),
sample_rate=self.sample_rate(),
channels=self.channels(),
channel_mask=int(self.channel_mask()),
bits_per_sample=self.bits_per_sample())
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