#!/usr/bin/perl -w

# NOTE: This is obsolete!  Mplayer since 1.0_rc2 has a scaletempo audio filter.

# Play media at different speeds without changing audio pitch.
#
# Usage: fastplay <speed> <mplayer args>
# eg: fastplay 1.6 clip.avi
#
# Requires that your system have /dev/fd/# file descriptor accessors
#
# XXX This is a bloody mess.  It should be re-written in scsh.
#
# Pipe diagram:
#
# mplayer1 --> <split> --> sox1 --> soundstretch --> sox2 --> /dev/dsp
#               |           ^
#               |           : (rate information)
#               v           :
#           mplayer2 --> <parse>
#
# mplayer1 reads the media file, displays the video, and dumps the
#          audio into this crazy pipeline
# mplayer2 just tells us what the audio samplerate is.
# sox1     back-converts the audio to the correct rate, undoing the
#          effects of mplayer1's -speed
# soundstretch does the sound stretching
# sox2     dumps the audio into the sound device

use POSIX qw(pipe);

$sounddevice = "/dev/dsp";
$syncmagic = 9000;
$speed = shift @ARGV;
$delay = 1 / $speed;

($READFROMMPLAYER1,$MPLAYER1WRITES) = pipe;
if (fork) {
	POSIX::close $READFROMMPLAYER1;
	# Launch mplayer
	exec "mplayer", "-autosync", $syncmagic, "-delay", $delay, "-speed", $speed, "-ao", "pcm:waveheader:file=/dev/fd/$MPLAYER1WRITES", @ARGV;
;
	die "exec failed";
} else {
	POSIX::close $MPLAYER1WRITES;
	# Split the stream.  Send the first block to mplayer2 to extract
	# the audio sample rate from it.  Send the complete stream to sox1.
	($SOX1READS, $WRITETOSOX1) = pipe;
	$blocksize = 4096;
	open READFROMMPLAYER1, "<&$READFROMMPLAYER1";
	sysread READFROMMPLAYER1,$buf,$blocksize;
	if (fork) {
		POSIX::close $SOX1READS;
		# Pass the stream through unmodified
		open WRITETOSOX1, ">&$WRITETOSOX1";
		syswrite WRITETOSOX1,$buf;
		while (sysread READFROMMPLAYER1,$buf,$blocksize) {
			syswrite WRITETOSOX1,$buf;
		}
		close (READFROMMPLAYER1);
		close (WRITETOSOX1);
		POSIX::close $READFROMMPLAYER1;
		POSIX::close $WRITETOSOX1;
		exit;
	} else {
		POSIX::close $WRITETOSOX1;
		# Duplicate the wav header and give it to another mplayer. (Is
		# there a less heavy-weight program that could be used here?)
		($MPLAYER2READS, $WRITETOMPLAYER2) = pipe;
		($READFROMMPLAYER2, $MPLAYER2WRITES) = pipe;
		if (fork) {
			POSIX::close $MPLAYER2READS;
			POSIX::close $READFROMMPLAYER2;
			POSIX::close $MPLAYER2WRITES;
			# Write the first chunk to mplayer
			open WRITETOMPLAYER2, ">&$WRITETOMPLAYER2";
			syswrite WRITETOMPLAYER2,$buf;
			close WRITETOMPLAYER2;
			POSIX::close $WRITETOMPLAYER2;
			exit;
		} elsif (fork) {
			POSIX::close $WRITETOMPLAYER2;
			POSIX::close $READFROMMPLAYER2;
			# Launch mplayer
			open STDOUT, ">&$MPLAYER2WRITES";
			open STDERR, ">&$MPLAYER2WRITES";
			exec "mplayer -demuxer audio -ao null /dev/fd/$MPLAYER2READS";
			die "exec failed";
		} else {
			POSIX::close $MPLAYER2READS;
			POSIX::close $WRITETOMPLAYER2;
			POSIX::close $MPLAYER2WRITES;
			# Parse mplayer's output
			open READFROMMPLAYER2, "<&$READFROMMPLAYER2";
			while (<READFROMMPLAYER2>) {
				if (/^AUDIO: ([0-9]+) Hz/) {
					$wrongsamplerate = $1;
					$rightsamplerate = $wrongsamplerate / $speed;
					close READFROMMPLAYER2;
					POSIX::close $READFROMMPLAYER2;

					# Found the sample rate.  Launch 
					# 1) sox to change the rate in the wav header
					# 2) soundstretch to do the stretching
					# 3) Another sox to shunt it to the output device
					($SOUNDSTRETCHREADSFROMSOX1,$SOX1WRITESTOSOUNDSTRETCH) = pipe;
					($SOX2READSFROMSOUNDSTRETCH,$SOUNDSTRETCHWRITESTOSOX2) = pipe;
					if (fork) {
						POSIX::close $SOUNDSTRETCHREADSFROMSOX1;
						POSIX::close $SOX2READSFROMSOUNDSTRETCH;
						POSIX::close $SOUNDSTRETCHWRITESTOSOX2;
						exec "sox -t wav -r $rightsamplerate /dev/fd/$SOX1READS -t wav /dev/fd/$SOX1WRITESTOSOUNDSTRETCH";
						die "exec failed";
					} elsif (fork) {
						POSIX::close $SOX1WRITESTOSOUNDSTRETCH;
						POSIX::close $SOX2READSFROMSOUNDSTRETCH;
						exec "soundstretch /dev/fd/$SOUNDSTRETCHREADSFROMSOX1 /dev/fd/$SOUNDSTRETCHWRITESTOSOX2 -tempo=".(($speed - 1) * 100);
						die "exec failed";
					} else {
						POSIX::close $SOUNDSTRETCHREADSFROMSOX1;
						POSIX::close $SOX1WRITESTOSOUNDSTRETCH;
						POSIX::close $SOUNDSTRETCHWRITESTOSOX2;
						exec "sox -t wav /dev/fd/$SOX2READSFROMSOUNDSTRETCH -t ossdsp -w -s $sounddevice";
						die "exec failed";

					}
					
				}
			}
			die "MPlayer output did not contain the magic string";
		}
	}
}