def __init__(self, filename, file=None):
        if file is not None:
            raise NotImplementedError('TODO: Load from file stream')

        self._file = av.avbin_open_filename(asbytes_filename(filename))
        if not self._file:
            raise AVbinException('Could not open "%s"' % filename)

        self._video_stream = None
        self._video_stream_index = -1
        self._audio_stream = None
        self._audio_stream_index = -1

        file_info = AVbinFileInfo()
        file_info.structure_size = ctypes.sizeof(file_info)
        av.avbin_file_info(self._file, ctypes.byref(file_info))
        self._duration = timestamp_from_avbin(file_info.duration)

        self.info = SourceInfo()
        self.info.title = file_info.title
        self.info.author = file_info.author
        self.info.copyright = file_info.copyright
        self.info.comment = file_info.comment
        self.info.album = file_info.album
        self.info.year = file_info.year
        self.info.track = file_info.track
        self.info.genre = file_info.genre

        # Pick the first video and audio streams found, ignore others.
        for i in range(file_info.n_streams):
            info = AVbinStreamInfo8()
            info.structure_size = ctypes.sizeof(info)
            av.avbin_stream_info(self._file, i, info)

            if (info.type == AVBIN_STREAM_TYPE_VIDEO and 
                not self._video_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.video_format = VideoFormat(
                    width=info.u.video.width,
                    height=info.u.video.height)
                if info.u.video.sample_aspect_num != 0:
                    self.video_format.sample_aspect = (
                        float(info.u.video.sample_aspect_num) /
                            info.u.video.sample_aspect_den)
                if _have_frame_rate:
                    self.video_format.frame_rate = (
                        float(info.u.video.frame_rate_num) / 
                            info.u.video.frame_rate_den)
                self._video_stream = stream
                self._video_stream_index = i

            elif (info.type == AVBIN_STREAM_TYPE_AUDIO and
                  info.u.audio.sample_bits in (8, 16) and
                  info.u.audio.channels in (1, 2) and 
                  not self._audio_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.audio_format = AudioFormat(
                    channels=info.u.audio.channels,
                    sample_size=info.u.audio.sample_bits,
                    sample_rate=info.u.audio.sample_rate)
                self._audio_stream = stream
                self._audio_stream_index = i

        self._packet = AVbinPacket()
        self._packet.structure_size = ctypes.sizeof(self._packet)
        self._packet.stream_index = -1

        self._events = []

        # Timestamp of last video packet added to decoder queue.
        self._video_timestamp = 0
        self._buffered_audio_data = []

        if self.audio_format:
            self._audio_buffer = \
                (ctypes.c_uint8 * av.avbin_get_audio_buffer_size())()
            
        if self.video_format:
            self._video_packets = []
            self._decode_thread = WorkerThread()
            self._decode_thread.start()
            self._condition = threading.Condition()
Beispiel #2
0
    def __init__(self, filename, file=None):
        if file is not None:
            raise NotImplementedError('TODO: Load from file stream')

        self._file = av.avbin_open_filename(filename)
        if not self._file:
            raise AVbinException('Could not open "%s"' % filename)

        self._video_stream = None
        self._video_stream_index = -1
        self._audio_stream = None
        self._audio_stream_index = -1

        file_info = AVbinFileInfo()
        file_info.structure_size = ctypes.sizeof(file_info)
        av.avbin_file_info(self._file, ctypes.byref(file_info))
        self._duration = timestamp_from_avbin(file_info.duration)

        self.info = SourceInfo()
        self.info.title = file_info.title
        self.info.author = file_info.author
        self.info.copyright = file_info.copyright
        self.info.comment = file_info.comment
        self.info.album = file_info.album
        self.info.year = file_info.year
        self.info.track = file_info.track
        self.info.genre = file_info.genre

        # Pick the first video and audio streams found, ignore others.
        for i in range(file_info.n_streams):
            info = AVbinStreamInfo8()
            info.structure_size = ctypes.sizeof(info)
            av.avbin_stream_info(self._file, i, info)

            if (info.type == AVBIN_STREAM_TYPE_VIDEO and 
                not self._video_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.video_format = VideoFormat(
                    width=info.u.video.width,
                    height=info.u.video.height)
                if info.u.video.sample_aspect_num != 0:
                    self.video_format.sample_aspect = (
                        float(info.u.video.sample_aspect_num) /
                            info.u.video.sample_aspect_den)
                if _have_frame_rate:
                    self.video_format.frame_rate = (
                        float(info.u.video.frame_rate_num) / 
                            info.u.video.frame_rate_den)
                self._video_stream = stream
                self._video_stream_index = i

            elif (info.type == AVBIN_STREAM_TYPE_AUDIO and
                  info.u.audio.sample_bits in (8, 16) and
                  info.u.audio.channels in (1, 2) and 
                  not self._audio_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.audio_format = AudioFormat(
                    channels=info.u.audio.channels,
                    sample_size=info.u.audio.sample_bits,
                    sample_rate=info.u.audio.sample_rate)
                self._audio_stream = stream
                self._audio_stream_index = i

        self._packet = AVbinPacket()
        self._packet.structure_size = ctypes.sizeof(self._packet)
        self._packet.stream_index = -1

        self._events = []

        # Timestamp of last video packet added to decoder queue.
        self._video_timestamp = 0
        self._buffered_audio_data = []

        if self.audio_format:
            self._audio_buffer = \
                (ctypes.c_uint8 * av.avbin_get_audio_buffer_size())()
            
        if self.video_format:
            self._video_packets = []
            self._decode_thread = WorkerThread()
            self._decode_thread.start()
            self._condition = threading.Condition()
class AVbinSource(StreamingSource):
    def __init__(self, filename, file=None):
        if file is not None:
            raise NotImplementedError('TODO: Load from file stream')

        self._file = av.avbin_open_filename(asbytes_filename(filename))
        if not self._file:
            raise AVbinException('Could not open "%s"' % filename)

        self._video_stream = None
        self._video_stream_index = -1
        self._audio_stream = None
        self._audio_stream_index = -1

        file_info = AVbinFileInfo()
        file_info.structure_size = ctypes.sizeof(file_info)
        av.avbin_file_info(self._file, ctypes.byref(file_info))
        self._duration = timestamp_from_avbin(file_info.duration)

        self.info = SourceInfo()
        self.info.title = file_info.title
        self.info.author = file_info.author
        self.info.copyright = file_info.copyright
        self.info.comment = file_info.comment
        self.info.album = file_info.album
        self.info.year = file_info.year
        self.info.track = file_info.track
        self.info.genre = file_info.genre

        # Pick the first video and audio streams found, ignore others.
        for i in range(file_info.n_streams):
            info = AVbinStreamInfo8()
            info.structure_size = ctypes.sizeof(info)
            av.avbin_stream_info(self._file, i, info)

            if (info.type == AVBIN_STREAM_TYPE_VIDEO and 
                not self._video_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.video_format = VideoFormat(
                    width=info.u.video.width,
                    height=info.u.video.height)
                if info.u.video.sample_aspect_num != 0:
                    self.video_format.sample_aspect = (
                        float(info.u.video.sample_aspect_num) /
                            info.u.video.sample_aspect_den)
                if _have_frame_rate:
                    self.video_format.frame_rate = (
                        float(info.u.video.frame_rate_num) / 
                            info.u.video.frame_rate_den)
                self._video_stream = stream
                self._video_stream_index = i

            elif (info.type == AVBIN_STREAM_TYPE_AUDIO and
                  info.u.audio.sample_bits in (8, 16) and
                  info.u.audio.channels in (1, 2) and 
                  not self._audio_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.audio_format = AudioFormat(
                    channels=info.u.audio.channels,
                    sample_size=info.u.audio.sample_bits,
                    sample_rate=info.u.audio.sample_rate)
                self._audio_stream = stream
                self._audio_stream_index = i

        self._packet = AVbinPacket()
        self._packet.structure_size = ctypes.sizeof(self._packet)
        self._packet.stream_index = -1

        self._events = []

        # Timestamp of last video packet added to decoder queue.
        self._video_timestamp = 0
        self._buffered_audio_data = []

        if self.audio_format:
            self._audio_buffer = \
                (ctypes.c_uint8 * av.avbin_get_audio_buffer_size())()
            
        if self.video_format:
            self._video_packets = []
            self._decode_thread = WorkerThread()
            self._decode_thread.start()
            self._condition = threading.Condition()

    def __del__(self):
        if _debug:
            print 'del avbin source'
        try:
            if self._video_stream:
                av.avbin_close_stream(self._video_stream)
            if self._audio_stream:
                av.avbin_close_stream(self._audio_stream)
            av.avbin_close_file(self._file)
        except:
            pass

    # XXX TODO call this / add to source api
    def delete(self):
        if self.video_format:
            self._decode_thread.stop()

    def seek(self, timestamp):
        if _debug:
            print 'AVbin seek', timestamp
        av.avbin_seek_file(self._file, timestamp_to_avbin(timestamp))

        self._audio_packet_size = 0
        del self._events[:]
        del self._buffered_audio_data[:]

        if self.video_format:
            self._video_timestamp = 0
            self._condition.acquire()
            for packet in self._video_packets:
                packet.image = None
            self._condition.notify()
            self._condition.release()
            del self._video_packets[:]

            self._decode_thread.clear_jobs()

    def _get_packet(self):
        # Read a packet into self._packet.  Returns True if OK, False if no
        # more packets are in stream.
        return av.avbin_read(self._file, self._packet) == AVBIN_RESULT_OK

    def _process_packet(self):
        # Returns (packet_type, packet), where packet_type = 'video' or
        # 'audio'; and packet is VideoPacket or AudioData.  In either case,
        # packet is buffered or queued for decoding; no further action is
        # necessary.  Returns (None, None) if packet was neither type.

        if self._packet.stream_index == self._video_stream_index:
            if self._packet.timestamp < 0:
                # XXX TODO
                # AVbin needs hack to decode timestamp for B frames in
                # some containers (OGG?).  See
                # http://www.dranger.com/ffmpeg/tutorial05.html
                # For now we just drop these frames.
                return None, None

            video_packet = VideoPacket(self._packet)

            if _debug:
                print 'Created and queued frame %d (%f)' % \
                    (video_packet.id, video_packet.timestamp)

            self._video_timestamp = max(self._video_timestamp,
                                        video_packet.timestamp)
            self._video_packets.append(video_packet)
            self._decode_thread.put_job(
                lambda: self._decode_video_packet(video_packet))

            return 'video', video_packet

        elif self._packet.stream_index == self._audio_stream_index:
            audio_data = self._decode_audio_packet()
            if audio_data:
                if _debug:
                    print 'Got an audio packet at', audio_data.timestamp
                self._buffered_audio_data.append(audio_data)
                return 'audio', audio_data

        return None, None

    def get_audio_data(self, bytes):
        try:
            audio_data = self._buffered_audio_data.pop(0)
            audio_data_timeend = audio_data.timestamp + audio_data.duration
        except IndexError:
            audio_data = None
            audio_data_timeend = self._video_timestamp + 1

        if _debug:
            print 'get_audio_data'

        have_video_work = False

        # Keep reading packets until we have an audio packet and all the
        # associated video packets have been enqueued on the decoder thread.
        while not audio_data or (
            self._video_stream and self._video_timestamp < audio_data_timeend):
            if not self._get_packet():
                break

            packet_type, packet = self._process_packet()

            if packet_type == 'video':
                have_video_work = True
            elif not audio_data and packet_type == 'audio':
                audio_data = self._buffered_audio_data.pop(0)
                if _debug:
                    print 'Got requested audio packet at', audio_data.timestamp
                audio_data_timeend = audio_data.timestamp + audio_data.duration

        if have_video_work:
            # Give decoder thread a chance to run before we return this audio
            # data.
            time.sleep(0)

        if not audio_data:
            if _debug:
                print 'get_audio_data returning None'
            return None

        while self._events and self._events[0].timestamp <= audio_data_timeend:
            event = self._events.pop(0)
            if event.timestamp >= audio_data.timestamp:
                event.timestamp -= audio_data.timestamp
                audio_data.events.append(event)

        if _debug:
            print 'get_audio_data returning ts %f with events' % \
                audio_data.timestamp, audio_data.events
            print 'remaining events are', self._events
        return audio_data

    def _decode_audio_packet(self):
        packet = self._packet
        size_out = ctypes.c_int(len(self._audio_buffer))

        while True:
            audio_packet_ptr = ctypes.cast(packet.data, ctypes.c_void_p)
            audio_packet_size = packet.size

            used = av.avbin_decode_audio(self._audio_stream,
                audio_packet_ptr, audio_packet_size,
                self._audio_buffer, size_out)

            if used < 0:
                self._audio_packet_size = 0
                break

            audio_packet_ptr.value += used
            audio_packet_size -= used

            if size_out.value <= 0:
                continue

            # XXX how did this ever work?  replaced with copy below
            # buffer = ctypes.string_at(self._audio_buffer, size_out)

            # XXX to actually copy the data.. but it never used to crash, so
            # maybe I'm  missing something
            buffer = ctypes.create_string_buffer(size_out.value)
            ctypes.memmove(buffer, self._audio_buffer, len(buffer))
            buffer = buffer.raw

            duration = float(len(buffer)) / self.audio_format.bytes_per_second
            self._audio_packet_timestamp = \
                timestamp = timestamp_from_avbin(packet.timestamp)
            return AudioData(buffer, len(buffer), timestamp, duration, []) 

    def _decode_video_packet(self, packet):
        width = self.video_format.width
        height = self.video_format.height
        pitch = width * 3
        buffer = (ctypes.c_uint8 * (pitch * height))()
        result = av.avbin_decode_video(self._video_stream, 
                                       packet.data, packet.size, 
                                       buffer)
        if result < 0:
            image_data = None
        else:
            image_data = image.ImageData(width, height, 'RGB', buffer, pitch)
            
        packet.image = image_data

        # Notify get_next_video_frame() that another one is ready.
        self._condition.acquire()
        self._condition.notify()
        self._condition.release()

    def _ensure_video_packets(self):
        '''Process packets until a video packet has been queued (and begun
        decoding).  Return False if EOS.
        '''
        if not self._video_packets:
            if _debug:
                print 'No video packets...'
            # Read ahead until we have another video packet
            self._get_packet()
            packet_type, _ = self._process_packet()
            while packet_type and packet_type != 'video':
                self._get_packet()
                packet_type, _ = self._process_packet()
            if not packet_type:
                return False

            if _debug:
                print 'Queued packet', _
        return True

    def get_next_video_timestamp(self):
        if not self.video_format:
            return

        if self._ensure_video_packets():
            if _debug:
                print 'Next video timestamp is', self._video_packets[0].timestamp
            return self._video_packets[0].timestamp

    def get_next_video_frame(self):
        if not self.video_format:
            return

        if self._ensure_video_packets():
            packet = self._video_packets.pop(0)
            if _debug:
                print 'Waiting for', packet

            # Block until decoding is complete
            self._condition.acquire()
            while packet.image == 0:
                self._condition.wait()
            self._condition.release()

            if _debug:
                print 'Returning', packet
            return packet.image
Beispiel #4
0
class AVbinSource(StreamingSource):
    def __init__(self, filename, file=None):
        if file is not None:
            raise NotImplementedError('TODO: Load from file stream')

        self._file = av.avbin_open_filename(filename)
        if not self._file:
            raise AVbinException('Could not open "%s"' % filename)

        self._video_stream = None
        self._video_stream_index = -1
        self._audio_stream = None
        self._audio_stream_index = -1

        file_info = AVbinFileInfo()
        file_info.structure_size = ctypes.sizeof(file_info)
        av.avbin_file_info(self._file, ctypes.byref(file_info))
        self._duration = timestamp_from_avbin(file_info.duration)

        self.info = SourceInfo()
        self.info.title = file_info.title
        self.info.author = file_info.author
        self.info.copyright = file_info.copyright
        self.info.comment = file_info.comment
        self.info.album = file_info.album
        self.info.year = file_info.year
        self.info.track = file_info.track
        self.info.genre = file_info.genre

        # Pick the first video and audio streams found, ignore others.
        for i in range(file_info.n_streams):
            info = AVbinStreamInfo8()
            info.structure_size = ctypes.sizeof(info)
            av.avbin_stream_info(self._file, i, info)

            if (info.type == AVBIN_STREAM_TYPE_VIDEO and 
                not self._video_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.video_format = VideoFormat(
                    width=info.u.video.width,
                    height=info.u.video.height)
                if info.u.video.sample_aspect_num != 0:
                    self.video_format.sample_aspect = (
                        float(info.u.video.sample_aspect_num) /
                            info.u.video.sample_aspect_den)
                if _have_frame_rate:
                    self.video_format.frame_rate = (
                        float(info.u.video.frame_rate_num) / 
                            info.u.video.frame_rate_den)
                self._video_stream = stream
                self._video_stream_index = i

            elif (info.type == AVBIN_STREAM_TYPE_AUDIO and
                  info.u.audio.sample_bits in (8, 16) and
                  info.u.audio.channels in (1, 2) and 
                  not self._audio_stream):

                stream = av.avbin_open_stream(self._file, i)
                if not stream:
                    continue

                self.audio_format = AudioFormat(
                    channels=info.u.audio.channels,
                    sample_size=info.u.audio.sample_bits,
                    sample_rate=info.u.audio.sample_rate)
                self._audio_stream = stream
                self._audio_stream_index = i

        self._packet = AVbinPacket()
        self._packet.structure_size = ctypes.sizeof(self._packet)
        self._packet.stream_index = -1

        self._events = []

        # Timestamp of last video packet added to decoder queue.
        self._video_timestamp = 0
        self._buffered_audio_data = []

        if self.audio_format:
            self._audio_buffer = \
                (ctypes.c_uint8 * av.avbin_get_audio_buffer_size())()
            
        if self.video_format:
            self._video_packets = []
            self._decode_thread = WorkerThread()
            self._decode_thread.start()
            self._condition = threading.Condition()

    def __del__(self):
        if _debug:
            print 'del avbin source'
        try:
            if self._video_stream:
                av.avbin_close_stream(self._video_stream)
            if self._audio_stream:
                av.avbin_close_stream(self._audio_stream)
            av.avbin_close_file(self._file)
        except:
            pass

    # XXX TODO call this / add to source api
    def delete(self):
        if self.video_format:
            self._decode_thread.stop()

    def seek(self, timestamp):
        if _debug:
            print 'AVbin seek', timestamp
        av.avbin_seek_file(self._file, timestamp_to_avbin(timestamp))

        self._audio_packet_size = 0
        del self._events[:]
        del self._buffered_audio_data[:]

        if self.video_format:
            self._video_timestamp = 0
            self._condition.acquire()
            for packet in self._video_packets:
                packet.image = None
            self._condition.notify()
            self._condition.release()
            del self._video_packets[:]

            self._decode_thread.clear_jobs()

    def _get_packet(self):
        # Read a packet into self._packet.  Returns True if OK, False if no
        # more packets are in stream.
        return av.avbin_read(self._file, self._packet) == AVBIN_RESULT_OK

    def _process_packet(self):
        # Returns (packet_type, packet), where packet_type = 'video' or
        # 'audio'; and packet is VideoPacket or AudioData.  In either case,
        # packet is buffered or queued for decoding; no further action is
        # necessary.  Returns (None, None) if packet was neither type.

        if self._packet.stream_index == self._video_stream_index:
            if self._packet.timestamp < 0:
                # XXX TODO
                # AVbin needs hack to decode timestamp for B frames in
                # some containers (OGG?).  See
                # http://www.dranger.com/ffmpeg/tutorial05.html
                # For now we just drop these frames.
                return None, None

            video_packet = VideoPacket(self._packet)

            if _debug:
                print 'Created and queued frame %d (%f)' % \
                    (video_packet.id, video_packet.timestamp)

            self._video_timestamp = max(self._video_timestamp,
                                        video_packet.timestamp)
            self._video_packets.append(video_packet)
            self._decode_thread.put_job(
                lambda: self._decode_video_packet(video_packet))

            return 'video', video_packet

        elif self._packet.stream_index == self._audio_stream_index:
            audio_data = self._decode_audio_packet()
            if audio_data:
                if _debug:
                    print 'Got an audio packet at', audio_data.timestamp
                self._buffered_audio_data.append(audio_data)
                return 'audio', audio_data

        return None, None

    def get_audio_data(self, bytes):
        try:
            audio_data = self._buffered_audio_data.pop(0)
            audio_data_timeend = audio_data.timestamp + audio_data.duration
        except IndexError:
            audio_data = None
            audio_data_timeend = self._video_timestamp + 1

        if _debug:
            print 'get_audio_data'

        have_video_work = False

        # Keep reading packets until we have an audio packet and all the
        # associated video packets have been enqueued on the decoder thread.
        while not audio_data or (
            self._video_stream and self._video_timestamp < audio_data_timeend):
            if not self._get_packet():
                break

            packet_type, packet = self._process_packet()

            if packet_type == 'video':
                have_video_work = True
            elif not audio_data and packet_type == 'audio':
                audio_data = self._buffered_audio_data.pop(0)
                if _debug:
                    print 'Got requested audio packet at', audio_data.timestamp
                audio_data_timeend = audio_data.timestamp + audio_data.duration

        if have_video_work:
            # Give decoder thread a chance to run before we return this audio
            # data.
            time.sleep(0)

        if not audio_data:
            if _debug:
                print 'get_audio_data returning None'
            return None

        while self._events and self._events[0].timestamp <= audio_data_timeend:
            event = self._events.pop(0)
            if event.timestamp >= audio_data.timestamp:
                event.timestamp -= audio_data.timestamp
                audio_data.events.append(event)

        if _debug:
            print 'get_audio_data returning ts %f with events' % \
                audio_data.timestamp, audio_data.events
            print 'remaining events are', self._events
        return audio_data

    def _decode_audio_packet(self):
        packet = self._packet
        size_out = ctypes.c_int(len(self._audio_buffer))

        while True:
            audio_packet_ptr = ctypes.cast(packet.data, ctypes.c_void_p)
            audio_packet_size = packet.size

            used = av.avbin_decode_audio(self._audio_stream,
                audio_packet_ptr, audio_packet_size,
                self._audio_buffer, size_out)

            if used < 0:
                self._audio_packet_size = 0
                break

            audio_packet_ptr.value += used
            audio_packet_size -= used

            if size_out.value <= 0:
                continue

            # XXX how did this ever work?  replaced with copy below
            # buffer = ctypes.string_at(self._audio_buffer, size_out)

            # XXX to actually copy the data.. but it never used to crash, so
            # maybe I'm  missing something
            buffer = ctypes.create_string_buffer(size_out.value)
            ctypes.memmove(buffer, self._audio_buffer, len(buffer))
            buffer = buffer.raw

            duration = float(len(buffer)) / self.audio_format.bytes_per_second
            self._audio_packet_timestamp = \
                timestamp = timestamp_from_avbin(packet.timestamp)
            return AudioData(buffer, len(buffer), timestamp, duration, []) 

    def _decode_video_packet(self, packet):
        width = self.video_format.width
        height = self.video_format.height
        pitch = width * 3
        buffer = (ctypes.c_uint8 * (pitch * height))()
        result = av.avbin_decode_video(self._video_stream, 
                                       packet.data, packet.size, 
                                       buffer)
        if result < 0:
            image_data = None
        else:
            image_data = image.ImageData(width, height, 'RGB', buffer, pitch)
            
        packet.image = image_data

        # Notify get_next_video_frame() that another one is ready.
        self._condition.acquire()
        self._condition.notify()
        self._condition.release()

    def _ensure_video_packets(self):
        '''Process packets until a video packet has been queued (and begun
        decoding).  Return False if EOS.
        '''
        if not self._video_packets:
            if _debug:
                print 'No video packets...'
            # Read ahead until we have another video packet
            self._get_packet()
            packet_type, _ = self._process_packet()
            while packet_type and packet_type != 'video':
                self._get_packet()
                packet_type, _ = self._process_packet()
            if not packet_type:
                return False

            if _debug:
                print 'Queued packet', _
        return True

    old_stamp = None

    def get_next_video_timestamp(self):
        if not self.video_format:
            return

        if self._ensure_video_packets():
            next_stamp = self._video_packets[0].timestamp

            if _debug:
                print 'Next video timestamp is', next_stamp

            if self.old_stamp == next_stamp:
                return
            self.old_stamp = next_stamp

            return next_stamp

    def get_next_video_frame(self):
        if not self.video_format:
            return

        if self._ensure_video_packets():
            packet = self._video_packets.pop(0)
            if _debug:
                print 'Waiting for', packet

            # Block until decoding is complete
            self._condition.acquire()
            while packet.image == 0:
                self._condition.wait()
            self._condition.release()

            if _debug:
                print 'Returning', packet
            return packet.image