--- amv.pl	2007/08/18 11:21:40	27
+++ amv.pl	2007/08/19 11:45:39	28
@@ -387,47 +387,170 @@
 	print ">> created $frame_nr ", $no_jpeg_header ? 'raw' : '', " jpeg $path ", -s $path, " bytes\n" if $verbose;
 }
 
-my ( $riff, $amv ) = x(12, 'Z4x4Z4');
-die "$path not RIFF but $riff" if $riff ne 'RIFF';
-die "$path not AMV but $amv" if $amv ne 'AMV ';
+#
+# IMA ADPCM decoder
+#
+
+my @index_adjust = ( -1, -1, -1, -1, 2, 4, 6, 8 );
+
+my @step_size = (
+	7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
+	19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
+	50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
+	130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
+	337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
+	876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
+	2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
+	5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
+	15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
+);
 
-my $apath = "$dump_dir/audio.wav";
-open(my $audio_fh, '>', $apath) || die "can't open audio file $apath: $!";
+my $pred_val = 0;
+my $step_idx = 0;
 
-print $audio_fh pack 'a4Va4a4VvvVVv4', (
-	# header 'RIFF', size
-	'RIFF',-1,
-	# type: 'WAVE'
-	'WAVE',
-	'fmt ',0x14,
-	# format: DVI (IMA) ADPCM Wave Type
-	0x11,
-	# channels
-	1,
-	# samples/sec
+# This code is "borrowed" from the ALSA library 
+# http://www.alsa-project.org
+
+sub adpcm_decode_sample {
+	my $code = shift;
+
+	my $pred_diff;	# Predicted difference to next sample
+	my $step;		# holds previous step_size value
+
+	# Separate sign and magnitude
+	my $sign = $code & 0x8;
+	$code &= 0x7;
+
+	# Computes pred_diff = (code + 0.5) * step / 4,
+	# but see comment in adpcm_coder.
+
+	$step = $step_size[$step_idx] || die "no step_size[$step_idx]";
+
+	# Compute difference and new predicted value 
+	$pred_diff = $step >> 3;
+	my $i = 0x4;
+	while( $i ) {
+		if ($code & $i) {
+			$pred_diff += $step;
+		}
+		$i >>= 1;
+		$step >>= 1;
+	}
+	$pred_val += $sign ? -$pred_diff : $pred_diff;
+
+	# Clamp output value 
+	if ($pred_val > 32767) {
+		$pred_val = 32767;
+	} elsif ($pred_val < -32768) {
+		$pred_val = -32768;
+	}
+
+	# Find new step_size index value
+	$step_idx += $index_adjust[$code];
+
+	if ($step_idx < 0) {
+		$step_idx = 0;
+	} elsif ($step_idx > 88) {
+		$step_idx = 88;
+	}
+	return $pred_val;
+}
+
+open(my $au_fh, '>', 'out.au') || die "can't open out.au: $!";
+print $au_fh pack 'a4N5', (
+	# magic
+	'.snd',
+	# data offset
+	24,
+	# data size
+	-1,
+	# encoding - 16-bit linear PCM
+	3,
+	# sample rate
 	22050,
-	# avg. bytes/sec (for esimation)
-	11567,
-	# block align (size of block)
-	0x800,
-	# bits per sample (mono data)
-	4,
-	# cbSize (ADPCM with 7 soefficient pairs)
-	2,
-	# nSamplesPerBlock
-	# (((nBlockAlign - (7 * nChannels)) * 8) / (wBitsPerSample * nChannels)) + 2
-	0x0ff9,
+	#channels
+	1,
 );
 
-print $audio_fh pack 'a4VVa4V', (
-	# time length of the data in samples
-	'fact',4,
-	220500,
-	#
-	'data',-1,
-);
+sub audio_frame {
+	my $data = shift || die "no data?";
+
+	my ( $origin, $index, $bytes ) = unpack 'ssL', substr($data,0,8);
 
-my $riff_header_len = tell($audio_fh);
+warn "audio_frame origin $origin index $index bytes $bytes\n";
+hex_dump( substr($data,0,8) );
+
+	$pred_val = $origin;
+	$step_idx = $index;
+
+	foreach my $b ( map { ord($_) } split(//, substr($data,8)) ) {
+		print $au_fh pack 'n', adpcm_decode_sample( $b >> 4 );		
+		print $au_fh pack 'n', adpcm_decode_sample( $b & 15 );		
+	}
+}
+
+
+sub x_audio_frame {
+	my $data = shift || die "no data?";
+
+	my $apath = sprintf("$dump_dir/%04d.wav", $frame_nr );
+	open(my $audio_fh, '>', $apath) || die "can't open audio file $apath: $!";
+
+	print $audio_fh pack 'a4Va4a4VvvVVv4', (
+		# header 'RIFF', size
+		'RIFF',-1,
+		# type: 'WAVE'
+		'WAVE',
+		'fmt ',0x14,
+		# format: DVI (IMA) ADPCM Wave Type
+		0x11,
+		# channels
+		1,
+		# samples/sec
+		22050,
+		# avg. bytes/sec (for esimation)
+		11567,
+		# block align (size of block)
+		0x800,
+		# bits per sample (mono data)
+		4,
+		# cbSize (ADPCM with 7 soefficient pairs)
+		2,
+		# nSamplesPerBlock
+		# (((nBlockAlign - (7 * nChannels)) * 8) / (wBitsPerSample * nChannels)) + 2
+		0x03f9,
+	);
+
+	print $audio_fh pack 'a4VVa4V', (
+		# time length of the data in samples
+		'fact',4,
+		220500,
+		#
+		'data',-1,
+	);
+
+	my $riff_header_len = tell($audio_fh);
+
+	print $audio_fh $data;
+
+	my $size = tell($audio_fh);
+	warn "## wav file $apath size: $size\n";
+
+	seek( $audio_fh, 4, 0 );
+	print $audio_fh pack("V", $size - 8);
+	seek( $audio_fh, $riff_header_len - 4, 0 );
+	print $audio_fh pack("V", $size - $riff_header_len);
+
+	close($audio_fh) || die "can't close audio file $apath: $!";
+}
+
+#
+# read AMV file
+#
+
+my ( $riff, $amv ) = x(12, 'Z4x4Z4');
+die "$path not RIFF but $riff" if $riff ne 'RIFF';
+die "$path not AMV but $amv" if $amv ne 'AMV ';
 
 while ( ! defined($d->{eof}) ) {
 	my ( $list, $name ) = x(12,'A4x4A4');
@@ -479,7 +602,7 @@
 			}
 
 			# remove 8 bytes of something
-			$audio_frame = substr( $audio_frame, 8 );
+#			$audio_frame = substr( $audio_frame, 8 );
 
 			if ( length($audio_frame) % 2 == 0 ) {
 				print "#### even sized frame!";
@@ -487,7 +610,7 @@
 			}
 
 #			print $audio_fh mp3_frame;
-			print $audio_fh $audio_frame || die "can't write audio frame in $apath: $!";
+			audio_frame( $audio_frame );
 
 			$frame_nr++;
 		};
@@ -500,14 +623,4 @@
 my $cmd = "ffmpeg -i $dump_dir/%04d.jpg -r 16 -y $dump_avi";
 system($cmd) == 0 || die "can't convert frames to avi using $cmd: $!";
 
-my $size = tell($audio_fh);
-warn "## wav file size: $size\n";
-
-seek( $audio_fh, 4, 0 );
-print $audio_fh pack("V", $size - 8);
-seek( $audio_fh, $riff_header_len - 4, 0 );
-print $audio_fh pack("V", $size - $riff_header_len);
-
-close($audio_fh) || die "can't close audio file $apath: $!";
-
-print ">>>> created $frame_nr frames $dump_avi ", -s $dump_avi, " and $apath ", -s $apath, "\n";
+print ">>>> created $frame_nr frames $dump_avi ", -s $dump_avi, "\n";