diff --git a/.gitignore b/.gitignore
index 36b13f1..ff1527d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -173,4 +173,4 @@ cython_debug/
 
 # PyPI configuration file
 .pypirc
-
+/test.mp4
diff --git a/mp4/__init__.py b/mp4/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/mp4/codec.py b/mp4/codec.py
new file mode 100644
index 0000000..ccb9e7f
--- /dev/null
+++ b/mp4/codec.py
@@ -0,0 +1,20 @@
+# RozK
+
+class NullCodec:
+    @property
+    def name(self):
+        return b"<None>"
+
+class Codec:
+    __slots__ = '_ref'
+
+    def __init__(self, ref):
+        self._ref = ref
+
+    @property
+    def _as_parameter_(self):
+        return self._ref
+
+    @property
+    def name(self):
+        return self._ref.contents.name
diff --git a/mp4/context.py b/mp4/context.py
new file mode 100644
index 0000000..c6fbbcd
--- /dev/null
+++ b/mp4/context.py
@@ -0,0 +1,54 @@
+# RozK
+
+from . import libav
+from .codec import Codec
+from .stream import NullStream, Stream
+from .packet import Packet
+
+class Context:
+    __slots__ = '_ref'
+
+    def __init__(self):
+        self._ref = libav.alloc_context()
+        if not self._ref:
+            raise MemoryError
+
+    def __del__(self):
+        if self._ref:
+            libav.free_context(self._ref)
+
+    @property
+    def _as_parameter_(self):
+        return self._ref
+
+    def open_input(self, url):
+        if not self._ref:
+            return
+        errcode = libav.open_input(self._ref, url)
+        if errcode < 0:
+            raise Exception(f"Failed to open: {url}")
+        errcode = libav.find_stream_info(self._ref)
+        if errcode < 0:
+            libav.close_input(self._ref)
+            raise Exception("Failed to find stream info")
+
+    def close_input(self):
+        if self._ref:
+            libav.close_input(self._ref)
+
+    def find_stream(self, type):
+        if not self._ref:
+            return NullStream()
+        index, codec_ref = libav.find_best_stream(self._ref, type)
+        if index < 0 or not codec_ref:
+            return NullStream()
+        return Stream(index, Codec(codec_ref))
+
+    def read_packet(self):
+        if not self._ref:
+            return None
+        packet = Packet()
+        errcode = libav.read_frame(self._ref, packet)
+        if errcode < 0:
+            return None
+        return packet
diff --git a/mp4/demuxer.py b/mp4/demuxer.py
new file mode 100644
index 0000000..fd6d881
--- /dev/null
+++ b/mp4/demuxer.py
@@ -0,0 +1,19 @@
+# RozK
+
+from . import libav
+from .context import Context
+
+class Demuxer:
+    __slots__ = 'context', 'video_stream', 'audio_stream'
+
+    def __init__(self, path):
+        self.context = Context()
+        self.context.open_input("file:" + path)
+        self.video_stream = self.context.find_stream(libav.AVMEDIA_TYPE_VIDEO)
+        self.audio_stream = self.context.find_stream(libav.AVMEDIA_TYPE_AUDIO)
+
+    def read_packet(self):
+        return self.context.read_packet()
+
+    def close(self):
+        self.context.close_input()
diff --git a/mp4/libav.py b/mp4/libav.py
new file mode 100644
index 0000000..3890650
--- /dev/null
+++ b/mp4/libav.py
@@ -0,0 +1,112 @@
+# RozK
+# https://www.ffmpeg.org/doxygen/trunk/group__libavf.html
+
+import ctypes
+
+_avformat = ctypes.cdll.LoadLibrary('libavformat.so')
+_avcodec = ctypes.cdll.LoadLibrary('libavcodec.so')
+
+class AVFormatContext(ctypes.Structure):
+    pass
+
+AVFormatContext_p = ctypes.POINTER(AVFormatContext)
+AVFormatContext_pp = ctypes.POINTER(AVFormatContext_p)
+
+_avformat.avformat_alloc_context.restype = AVFormatContext_p
+_avformat.avformat_alloc_context.argtypes = None
+
+def alloc_context():
+    return _avformat.avformat_alloc_context()
+
+_avformat.avformat_free_context.restype = None
+_avformat.avformat_free_context.argtypes = [AVFormatContext_p] # context
+
+def free_context(context):
+    _avformat.avformat_free_context(context)
+
+_avformat.avformat_open_input.restype = ctypes.c_int
+_avformat.avformat_open_input.argtypes = [
+    AVFormatContext_pp, # context
+    ctypes.c_char_p, # url
+    ctypes.c_void_p, # format
+    ctypes.POINTER(ctypes.c_void_p)] # options
+
+def open_input(context, url):
+    return _avformat.avformat_open_input(ctypes.byref(context), url.encode('ascii', 'ignore'), None, None)
+
+_avformat.avformat_close_input.restype = None
+_avformat.avformat_close_input.argtypes = [AVFormatContext_pp] # context
+
+def close_input(context):
+    _avformat.avformat_close_input(ctypes.byref(context))
+
+_avformat.avformat_find_stream_info.restype = ctypes.c_int
+_avformat.avformat_find_stream_info.argtypes = [
+    AVFormatContext_p, # context
+    ctypes.POINTER(ctypes.c_void_p)] # options
+
+def find_stream_info(context):
+    return _avformat.avformat_find_stream_info(context, None)
+
+AVMEDIA_TYPE_UNKNOWN = -1
+AVMEDIA_TYPE_VIDEO = 0
+AVMEDIA_TYPE_AUDIO = 1
+AVMEDIA_TYPE_DATA = 2
+AVMEDIA_TYPE_SUBTITLE = 3
+AVMEDIA_TYPE_ATTACHMENT = 4
+
+class AVCodec(ctypes.Structure):
+    _fields_ = [
+        ("name", ctypes.c_char_p),
+        ("long_name", ctypes.c_char_p)]
+        # ...
+
+AVCodec_p = ctypes.POINTER(AVCodec)
+AVCodec_pp = ctypes.POINTER(AVCodec_p)
+
+_avformat.av_find_best_stream.restype = ctypes.c_int
+_avformat.av_find_best_stream.argtypes = [
+    AVFormatContext_p, # context
+    ctypes.c_int, # type
+    ctypes.c_int, # wanted stream
+    ctypes.c_int, # related stream
+    AVCodec_pp, # decoder
+    ctypes.c_int] # flags
+
+def find_best_stream(context, type):
+    codec = AVCodec_p()
+    index = _avformat.av_find_best_stream(context, type, -1, -1, ctypes.byref(codec), 0)
+    return index, codec
+
+class AVPacket(ctypes.Structure):
+    _fields_ = [
+        ("buf", ctypes.c_void_p),
+        ("pts", ctypes.c_int64),
+        ("dts", ctypes.c_int64),
+        ("data", ctypes.c_void_p),
+        ("size", ctypes.c_int),
+        ("stream_index", ctypes.c_int)]
+        # ...
+
+AVPacket_p = ctypes.POINTER(AVPacket)
+AVPacket_pp = ctypes.POINTER(AVPacket_p)
+
+_avformat.av_packet_alloc.restype = AVPacket_p
+_avformat.av_packet_alloc.argtypes = None
+
+def packet_alloc():
+    return _avformat.av_packet_alloc()
+
+_avformat.av_packet_free.restype = None
+_avformat.av_packet_free.argtypes = [AVPacket_pp] # packet
+
+def packet_free(packet):
+    _avformat.av_packet_free(ctypes.byref(packet))
+
+_avformat.av_read_frame.restype = ctypes.c_int
+_avformat.av_read_frame.argtypes = [
+    AVFormatContext_p, # context
+    AVPacket_p] # packet
+
+def read_frame(context, packet):
+    return _avformat.av_read_frame(context, packet)
diff --git a/mp4/packet.py b/mp4/packet.py
new file mode 100644
index 0000000..c6aceab
--- /dev/null
+++ b/mp4/packet.py
@@ -0,0 +1,25 @@
+# RozK
+
+from . import libav
+
+class Packet:
+    __slots__ = '_ref'
+
+    def __init__(self):
+        self._ref = libav.packet_alloc()
+        if not self._ref:
+            raise MemoryError
+
+    def __del__(self):
+        if self._ref:
+            libav.packet_free(self._ref)
+
+    @property
+    def _as_parameter_(self):
+        return self._ref
+
+    @property
+    def stream_index(self):
+        if self._ref:
+            return self._ref.contents.stream_index
+        return -1
diff --git a/mp4/stream.py b/mp4/stream.py
new file mode 100644
index 0000000..25c0424
--- /dev/null
+++ b/mp4/stream.py
@@ -0,0 +1,25 @@
+# RozK
+
+from .codec import NullCodec
+
+class NullStream:
+    @property
+    def index(self):
+        return -1
+
+    @property
+    def codec(self):
+        return NullCodec()
+
+    def contains(self, packet):
+        return False
+
+class Stream:
+    __slots__ = 'index', 'codec'
+
+    def __init__(self, index, codec):
+        self.index = index
+        self.codec = codec
+
+    def contains(self, packet):
+        return (self.index == packet.stream_index)
diff --git a/pve.py b/pve.py
new file mode 100644
index 0000000..b00aea0
--- /dev/null
+++ b/pve.py
@@ -0,0 +1,21 @@
+# RozK
+
+from mp4.demuxer import Demuxer
+
+demuxer = Demuxer('test.mp4')
+
+print(demuxer.video_stream.codec.name)
+print(demuxer.audio_stream.codec.name)
+
+while True:
+    packet = demuxer.read_packet()
+    if packet is None:
+        break
+    if demuxer.video_stream.contains(packet):
+        continue
+    elif demuxer.audio_stream.contains(packet):
+        continue
+    else:
+        print("unkown packet")
+
+demuxer.close()