From 81dba1327121e0f62fdf42de61402979b7de5da6 Mon Sep 17 00:00:00 2001
From: Sigrid <ftrvxmtrx@gmail.com>
Date: Wed, 12 Aug 2020 10:43:46 +0200
Subject: [PATCH] audio/mp3dec: add -s SECONDS option

---
 sys/man/1/audio                 |  3 +++
 sys/src/cmd/audio/mp3dec/main.c | 26 +++++++++++++++++++++++++-
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/sys/man/1/audio b/sys/man/1/audio
index 5bbe072a5..511182c98 100644
--- a/sys/man/1/audio
+++ b/sys/man/1/audio
@@ -4,6 +4,9 @@ mp3dec, mp3enc, oggdec, oggenc, flacdec, sundec, wavdec, pcmconv, mixfs \- decod
 .SH SYNOPSIS
 .B audio/mp3dec
 [
+.B -s
+.I seconds
+] [
 .B -d
 ]
 .br
diff --git a/sys/src/cmd/audio/mp3dec/main.c b/sys/src/cmd/audio/mp3dec/main.c
index ee90ce0bd..20d2d0774 100644
--- a/sys/src/cmd/audio/mp3dec/main.c
+++ b/sys/src/cmd/audio/mp3dec/main.c
@@ -7,6 +7,7 @@
 
 /* Current input file */
 vlong offset;
+double seekto = 0.0, curpos = 0.0;
 int debug = 0;
 int ifd = -1;
 
@@ -29,6 +30,22 @@ input(void *, struct mad_stream *stream)
 	return MAD_FLOW_CONTINUE;
 }
 
+static enum mad_flow
+header(void *, struct mad_header const* header)
+{
+	if(seekto > 0 && (header->duration.seconds > 0 || header->duration.fraction > 0)){
+		double dur = header->duration.seconds + (double)header->duration.fraction / MAD_TIMER_RESOLUTION;
+		seekto -= dur;
+		if(seekto > 0){
+			curpos += dur;
+			return MAD_FLOW_IGNORE;
+		}
+		fprint(2, "time: %g\n", curpos);
+		seekto = 0;
+	}
+	return MAD_FLOW_CONTINUE;
+}
+
 static enum mad_flow
 output(void *, struct mad_header const* header, struct mad_pcm *pcm)
 {
@@ -39,6 +56,9 @@ output(void *, struct mad_header const* header, struct mad_pcm *pcm)
 	int i, j, n;
 	uchar *p;
 
+	if(seekto > 0)
+		return MAD_FLOW_CONTINUE;
+
 	/* start converter if format changed */
 	if(rate != pcm->samplerate || chans != pcm->channels){
 		int pid, pfd[2];
@@ -145,11 +165,15 @@ main(int argc, char **argv)
 	case 'd':
 		debug++;
 		break;
+	case 's':
+		seekto = atof(EARGF(usage()));
+		if(seekto >= 0.0)
+			break;
 	default:
 		usage();
 	}ARGEND
 
-	mad_decoder_init(&decoder, nil, input, nil, nil, output, error, nil);
+	mad_decoder_init(&decoder, nil, input, header, nil, output, error, nil);
 	mad_decoder_run(&decoder, MAD_DECODER_MODE_SYNC);
 	mad_decoder_finish(&decoder);