read flv data

flv.py

import struct


class FLVParsingError(Exception):

    def __init__(self, value):
        self.value = value

    def __str__(self):
        return repr(self.value)

class FLVTag(object):

    TYPE_AUDIO = 0x08
    TYPE_VIDEO = 0x09
    TYPE_META = 0x12
    VALID_TYPE = [TYPE_AUDIO, TYPE_VIDEO, TYPE_META]

    def __init__(self, file):

        pos = file.tell()
        while not self._find_tag(file):
            pos = pos + 1
            file.seek(pos)

        if not self._valid():
            return

        self.body = file.read(self.body_length)

    def _find_tag(self, file):
        self.prev_tag_size = self.unpack("4b", file.read(4))
        self.type = self.unpack("b", file.read(1))
        self.body_length = self.uint24be(file.read(3))
        self.timestamp = self.uint24be(file.read(3))
        self.padding = self.unpack("4b", file.read(4))
        return self._valid()

    def _valid(self):
        return self.padding == 0 and self.type in FLVTag.VALID_TYPE

    def uint24be(self, data):
        return self.unpack(">I", '\x00' + data)

    def unpack(self, format, data):
        unpacked = struct.unpack(format, data)
        #print unpacked
        return unpacked[0]

    def __str__(self):
        info = {}
        info['prev_tag_size'] = self.prev_tag_size
        info['type'] = self.type
        info['body_length'] = self.body_length
        info['timestamp'] = self.timestamp
        return repr(info)


class FLV(object):

    FLV_MARKER = "FLV"
    FLV_HEADER_SIZE = 9
    FLV_VERSION = 1
    FLV_TAG_HEADER_SIZE = 15

    def __init__(self, file):
        self.file = file
        self._validate_header()

    def _validate_header(self):
        header = self.file.read(FLV.FLV_HEADER_SIZE)
        print struct.unpack("9b", header)

        if FLV.FLV_MARKER == header[:3]:
            version = struct.unpack("b", header[3])[0]
            size = struct.unpack(">I", header[-4:])[0]

            valid = size == FLV.FLV_HEADER_SIZE
            valid = valid and version == FLV.FLV_VERSION
            if not valid:
                raise FLVParsingError("bad flv header")

    def read(self):
        while True:
            try:
                tag = FLVTag(self.file)
                yield tag
            except Exception as e:
                break


if __name__ == "__main__":
    with open("test1.flv", "rb") as f:
        flv = FLV(f)
        for t in flv.read():
            print t