Python code to write FLAC mandatory headers for a stream (adapted from mutagen code)

flac_haders.py

import struct
from StringIO import StringIO


def write_flac_header(sample_rate, channels, bits_per_sample):
    total_samples = 0
    f = StringIO()

    # write FLAC header
    f.write("fLaC")

    # write METADATA_BLOCK_HEADER(STREAMINFO)
    f.write(chr(128))
    f.write(struct.pack(">I", 34)[-3:])

    # write METADATA_BLOCK(STREAMINFO)
    f.write(struct.pack(">I", 4096)[-2:])
    f.write(struct.pack(">I", 4096)[-2:])
    f.write(struct.pack(">I", 0)[-3:])
    f.write(struct.pack(">I", 0)[-3:])

    # first 16 bits of sample rate
    f.write(struct.pack(">I", sample_rate >> 4)[-2:])
    # 4 bits sample, 3 channel, 1 bps
    byte = (sample_rate & 0xF) << 4
    byte += ((channels - 1) & 7) << 1
    byte += ((bits_per_sample - 1) >> 4) & 1
    f.write(chr(byte))
    # 4 bits of bps, 4 of sample count
    byte = ((bits_per_sample - 1) & 0xF) << 4
    byte += (total_samples >> 32) & 0xF
    f.write(chr(byte))
    # last 32 of sample count
    f.write(struct.pack(">I", 0 & 0xFFFFFFFFL))
    # MD5 signature (unknown)
    sig = 0
    f.write(struct.pack(
        ">4I", (sig >> 96) & 0xFFFFFFFFL, (sig >> 64) & 0xFFFFFFFFL,
               (sig >> 32) & 0xFFFFFFFFL, sig & 0xFFFFFFFFL))