playback_buffer.py

import sys
import time
import threading

class PlaybackBuffer:
    def __init__(self, buffer_size, debug=False):
        self.segments = []
        self.buffer_size = buffer_size
        self.buffer = 0 # Number of seconds in buffer
        self.current_rate = 0
        self.lock = threading.Lock()
        self.debug = debug

    def start(self):
        t = threading.Thread(target=PlaybackBuffer.run_forever, args=(self,))
        t.setDaemon(True)
        t.start()

    def _run_forever(self):
        interval = 0.5
        while True:
            time.sleep(interval)
            self.lock.acquire()
            if self.buffer > 0:
                self.buffer = self.buffer - 0.5
                self.debug_print("Drain buffer %f" % self.buffer)
            self.lock.release()

    def run_forever(self):
        try:
            self._run_forever()
        except Exception as e:
            print '----- error in buffer -----'
            print e
            import traceback
            traceback.print_exc()
            sys.stdout.flush()

    # Assume available_bytes is checked before adding
    def add_four_second_segment(self, nbytes_four_second):
        self.lock.acquire()
        self.buffer = self.buffer + 4 # Each buffer element is a 4 second chunk 
        self.debug_print("Add buffer %f" % self.buffer)
        self.lock.release()

    def available_bytes(self):
        available = 0
        self.lock.acquire()
        if (self.buffer <= self.buffer_size): # Buffer contains 240 seconds of video play
            available = 1
        self.lock.release()
        return available

    def debug_print(self, msg):
        if self.debug:
            print msg
            sys.stdout.flush()