我住在世界的另一端（现在是 GMT+1，现在是 GMT+13），我想念我以前的地面广播电台。它有一个 Shoutcast 流，我想简单地将它延迟 12 小时，以便在我想收听它时它始终可用，以使其时区与我的时区同步的方式。
我将其设想为在我的服务器主机上运行的脚本。
一种天真的方法只是在环形缓冲区中分配足够的内存来存储整个 12 小时的延迟，并通过管道输入 streamripper 的输出。但是流是 128kbps 的 mp3，这意味着 (128/8) * 60 * 60 = ~56MB/小时，或者整个 12 小时缓冲区的 675MB，这并不是那么实用。另外，我可能不得不处理我的服务器主机，只是在某个超时后终止进程。
那么，有哪些实际可行的策略呢？
你为什么不直接用 Ripshout 之类的流开膛手下载它呢？
流开膛手将是简单的方式，也可能是正确的方式，但如果你想用程序员的方式来做......
为了回答我自己的问题，这里有一个脚本，它每 30 分钟启动一次 cron 作业。它将传入流以 5 分钟的块（或由 FILE_SECONDS 设置）转储到特定目录。块边界与时钟同步，直到当前时间块结束时才开始写入，因此正在运行的 cronjobs 可以重叠而不会加倍数据或留下间隙。文件被命名为 (epoch time % number of seconds in 24 hours).str 。
我还没有制作播放器，但计划是将输出目录设置为可通过网络访问的某个位置，并编写一个在本地运行的脚本，该脚本使用与此处相同的时间戳计算代码来顺序访问（时间戳 12 小时前).str，将它们重新组合在一起，然后在本地设置为广播服务器。然后我可以将我的音乐播放器指向http://localhost:port并获取它。
编辑：具有超时和更好的错误条件检查的新版本，以及漂亮的日志文件。这目前在我的（便宜的）共享虚拟主机上运行顺利，没有问题。
#!/usr/bin/python
import time
import urllib
import datetime
import os
import socket
# number of seconds for each file
FILE_SECONDS = 300
# run for 30 minutes
RUN_TIME = 60*30
# size in bytes of each read block
# 16384 = 1 second
BLOCK_SIZE = 16384
MAX_TIMEOUTS = 10
# where to save the files
OUTPUT_DIRECTORY = "dir/"
# URL for original stream
URL = "http://url/path:port"
debug = True
log = None
socket.setdefaulttimeout(10)
class DatestampedWriter:
# output_path MUST have trailing '/'
def __init__(self, output_path, run_seconds ):
self.path = output_path
self.file = None
# needs to be -1 to avoid issue when 0 is a real timestamp
self.curr_timestamp = -1
self.running = False
# don't start until the _end_ of the current time block
# so calculate an initial timestamp as (now+FILE_SECONDS)
self.initial_timestamp = self.CalcTimestamp( FILE_SECONDS )
self.final_timestamp = self.CalcTimestamp( run_seconds )
if debug:
log = open(OUTPUT_DIRECTORY+"log_"+str(self.initial_timestamp)+".txt","w")
log.write("initial timestamp "+str(self.initial_timestamp)+", final "+str(self.final_timestamp)+" (diff "+str(self.final_timestamp-self.initial_timestamp)+")\n")
self.log = log
def Shutdown(self):
if self.file != None:
self.file.close()
# write out buf
# returns True when we should stop
def Write(self, buf):
# check that we have the correct file open
# get timestamp
timestamp = self.CalcTimestamp()
if not self.running :
# should we start?
if timestamp == self.initial_timestamp:
if debug:
self.log.write( "starting running now\n" )
self.log.flush()
self.running = True
# should we open a new file?
if self.running and timestamp != self.curr_timestamp:
if debug:
self.log.write( "new timestamp "+str(timestamp)+"\n" )
self.log.flush()
# close old file
if ( self.file != None ):
self.file.close()
# time to stop?
if ( self.curr_timestamp == self.final_timestamp ):
if debug:
self.log.write( " -- time to stop\n" )
self.log.flush()
self.running = False
return True
# open new file
filename = self.path+str(timestamp)+".str"
#if not os.path.exists(filename):
self.file = open(filename, "w")
self.curr_timestamp = int(timestamp)
#else:
# uh-oh
# if debug:
# self.log.write(" tried to open but failed, already there\n")
# self.running = False
# now write bytes
if self.running:
#print("writing "+str(len(buf)))
self.file.write( buf )
return False
def CalcTimestamp(self, seconds_offset=0):
t = datetime.datetime.now()
seconds = time.mktime(t.timetuple())+seconds_offset
# FILE_SECONDS intervals, 24 hour days
timestamp = seconds - ( seconds % FILE_SECONDS )
timestamp = timestamp % 86400
return int(timestamp)
writer = DatestampedWriter(OUTPUT_DIRECTORY, RUN_TIME)
writer_finished = False
# while been running for < (RUN_TIME + 5 minutes)
now = time.mktime(datetime.datetime.now().timetuple())
stop_time = now + RUN_TIME + 5*60
while not writer_finished and time.mktime(datetime.datetime.now().timetuple())<stop_time:
now = time.mktime(datetime.datetime.now().timetuple())
# open the stream
if debug:
writer.log.write("opening stream... "+str(now)+"/"+str(stop_time)+"\n")
writer.log.flush()
try:
u = urllib.urlopen(URL)
except socket.timeout:
if debug:
writer.log.write("timed out, sleeping 60 seconds\n")
writer.log.flush()
time.sleep(60)
continue
except IOError:
if debug:
writer.log.write("IOError, sleeping 60 seconds\n")
writer.log.flush()
time.sleep(60)
continue
# read 1 block of input
buf = u.read(BLOCK_SIZE)
timeouts = 0
while len(buf) > 0 and not writer_finished and now<stop_time and timeouts<MAX_TIMEOUTS:
# write to disc
writer_finished = writer.Write(buf)
# read 1 block of input
try:
buf = u.read(BLOCK_SIZE)
except socket.timeout:
# catch exception but do nothing about it
if debug:
writer.log.write("read timed out ("+str(timeouts)+")\n")
writer.log.flush()
timeouts = timeouts+1
now = time.mktime(datetime.datetime.now().timetuple())
# stream has closed,
if debug:
writer.log.write("read loop bailed out: timeouts "+str(timeouts)+", time "+str(now)+"\n")
writer.log.flush()
u.close();
# sleep 1 second before trying to open the stream again
time.sleep(1)
now = time.mktime(datetime.datetime.now().timetuple())
writer.Shutdown()