Only in v13: snd_ut.py
diff -ur v12/snddiv.py v13/snddiv.py
--- v12/snddiv.py	2020-09-23 20:59:26.000000000 +0900
+++ v13/snddiv.py	2022-05-02 18:32:46.842678228 +0900
@@ -10,15 +10,16 @@
 import dbg
 import arg
 
-def play_new(dat, inf, sudo_passwd='', r_rate=1.0):
+#nc_out = lambda s: cmd_ut.call( 'echo {} | nc -N localhost 7075'.format( s ) )
+
+def play_new( load_div, inf, sudo_passwd='', r_rate=1.0 ):
 	e = empty.new()
-	e.dat = dat
 	e.run = False
 	e.sec = 0
 	e.rbuf = ''
 	e.evt = thr.event_new()
 
-	last_sec = inf.byte_to_sec( len(dat) )
+	last_sec = load_div.all_sec
 
 	def proc_new():
 		cmd = 'play {} -'.format( inf.get_raw_opt(r_rate) )
@@ -50,10 +51,14 @@
 			update(s)
 
 	def wfunc(f):
-		try:
-			f.write(dat)
-		except:
-			pass
+		while True:
+			b = load_div.get_dat()
+			if not b:
+				break
+			try:
+				f.write( b )
+			except:
+				break
 		f.close()
 
 	proc = proc_new()
@@ -76,15 +81,27 @@
 
 	return empty.to_attr( e, locals() )
 
-def snd_new(data, sudo_passwd):
+def snd_new( data, sudo_passwd, cache ):
 	inf = data.inf
 	last_sec = inf.smp_to_sec( inf.smp_n )
 	dbg.out( 'last_sec={}'.format( last_sec ) )
 
-	b = data.get_bytes()
 	n = inf.byte_per_smp
-	smp_lst = list( map( lambda i: b[i*n:i*n+n], range( inf.smp_n ) ) )
-	smp_rlst = smp_lst[::-1]
+	b = None
+	smp_lst = None
+	smp_rlst = None
+
+	def bytes_to_smp( b ):
+		smp_n = len( b ) // n
+		return list( map( lambda i: b[ i * n : i * n + n ], range( smp_n ) ) )
+
+	def smp_to_bytes( lst ):
+		return b''.join( lst )
+
+	if cache:
+		b = data.get_bytes()
+		smp_lst = bytes_to_smp( b )
+		smp_rlst = smp_lst[::-1]
 
 	e = empty.new()
 	e.sec = 0
@@ -102,16 +119,23 @@
 		lst = get_smp_sec(sec, reverse)
 		if shift > 0:
 			lst = lst[:: 2**shift ]
-		return b''.join(lst)
+		return smp_to_bytes( lst )
 
 	def get_smp_from_to(sec_f, sec_t):
-		f = inf.smp_sec(sec_f)
-		t = inf.smp_sec(sec_t)
-		return smp_lst[f:t]
+		if cache:
+			f = inf.smp_sec(sec_f)
+			t = inf.smp_sec(sec_t)
+			return smp_lst[f:t]
+
+		b = get_dat_from_to( sec_f, sec_t )
+		return bytes_to_smp( b )
 
 	def get_dat_from_to(sec_f, sec_t):
-		lst = get_smp_from_to(sec_f, sec_t)
-		return b''.join(lst)
+		if cache:
+			lst = get_smp_from_to(sec_f, sec_t)
+			return smp_to_bytes( lst )
+
+		return data.get_bytes( sec_f, sec_t, cache=False )
 
 	def get_sec():
 		add = 0
@@ -121,13 +145,59 @@
 				add = -add
 		return e.sec + add
 
+	def load_div_new( sec, reverse, shift ):
+		e = empty.new()
+		e.fin = False
+		e.sec = sec
+
+		all_sec = ( sec if reverse else last_sec - sec )
+
+		def get_dat():
+			if e.fin:
+			#if e.sec <= fin_sec if reverse else e.sec >= fin_sec:
+				return None
+
+			if cache:
+				e.fin = True
+				return get_dat_sec( e.sec, reverse, shift )
+
+			step_sec = 5.0
+
+			if reverse:
+				sec_t = e.sec
+				sec_f = max( e.sec - step_sec, 0 )
+				b = get_dat_from_to( sec_f, sec_t )
+				e.sec = sec_f
+				e.fin = ( e.sec <= 0 )
+			else:
+				sec_f = e.sec
+				sec_t = min( e.sec + step_sec, fin_sec )
+				b = get_dat_from_to( sec_f, sec_t )
+				e.sec = sec_t
+				e.fin = ( e.sec >= last_sec )
+
+			if not reverse and shift == 0:
+				return b
+
+			lst = bytes_to_smp( b )
+
+			if reverse:
+				lst = lst[ :: -1 ]
+
+			if shift > 0:
+				lst = lst[ :: 2 ** shift ]
+
+			return smp_to_bytes( lst )
+
+		return empty.add( e, locals() )
+
 	def start():
 		if e.play:
 			stop()
 
-		dat = get_dat_sec( e.sec, e.reverse, max(e.shift, 0) )
+		load_div = load_div_new( e.sec, e.reverse, max( e.shift, 0 ) )
 
-		e.play = play_new( dat, inf, sudo_passwd, min(2**e.shift, 1.0) )
+		e.play = play_new( load_div, inf, sudo_passwd, min(2**e.shift, 1.0) )
 		e.play.start()
 
 	def stop():
@@ -203,6 +273,7 @@
 
 	sudo_passwd = a.pop_str('-S')
 	silent = a.is_pop('-silent')
+	cache = a.is_pop( '-cache' )
 	filename_mp3 = a.pop()
 	if not filename_mp3:
 		dbg.help_exit( '[-g] [-S sudo_passwd] [-silent] filename_mp3' )
@@ -212,7 +283,7 @@
 
 	data = snd_ut.data_new(filename_mp3)
 
-	snd = snd_new(data, sudo_passwd)
+	snd = snd_new( data, sudo_passwd, cache )
 
 	rdr = io_ut.reader_new( sys.stdin, 1, no_buf=True )