Re: aplay patch to add a --seek parameter

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

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Clemens Ladisch <clemens@ladisch.de> writes:

> Please provide a Signed-off-by tag, document whether this option takes
> samples, frames, or (milli)seconds, and add this option to the man page.
> Furthermore, the code doesn't look as if it correctly skips over chunks
> in VOC files.

The --seek number is in bytes, so it assumes that the caller knows what
the internal structure of the file is.  For my usage (which is a simple
visual wave form editor), this makes sense, but specifying it in
milliseconds would probably be even more useful, I guess?

I'm not that familiar with the aplay internals, but so if someone who
are familiar were to transform the patch into "seek to millisecond X",
that would be nice.

Signed-off-by: Lars Magne Ingebrigtsen <larsi@gnus.org>


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--- aplay.c.orig	2011-01-31 15:19:55.000000000 +0100
+++ aplay.c	2011-04-16 02:45:43.000000000 +0200
@@ -86,6 +86,7 @@
 	unsigned int rate;
 } hwparams, rhwparams;
 static int timelimit = 0;
+static int seek_length = 0;
 static int quiet_mode = 0;
 static int file_type = FORMAT_DEFAULT;
 static int open_mode = 0;
@@ -186,6 +187,7 @@
 "-c, --channels=#        channels\n"
 "-f, --format=FORMAT     sample format (case insensitive)\n"
 "-r, --rate=#            sample rate\n"
+"-S, --seek=#            seek to position # (in bytes) before playing\n"
 "-d, --duration=#        interrupt after # seconds\n"
 "-M, --mmap              mmap stream\n"
 "-N, --nonblock          nonblocking mode\n"
@@ -404,7 +406,7 @@
 int main(int argc, char *argv[])
 {
 	int option_index;
-	static const char short_options[] = "hnlLD:qt:c:f:r:d:MNF:A:R:T:B:vV:IPC";
+	static const char short_options[] = "hnlLD:qt:c:f:r:S:d:MNF:A:R:T:B:vV:IPC";
 	static const struct option long_options[] = {
 		{"help", 0, 0, 'h'},
 		{"version", 0, 0, OPT_VERSION},
@@ -417,6 +419,7 @@
 		{"channels", 1, 0, 'c'},
 		{"format", 1, 0, 'f'},
 		{"rate", 1, 0, 'r'},
+		{"seek", 1, 0, 'S'},
 		{"duration", 1, 0 ,'d'},
 		{"mmap", 0, 0, 'M'},
 		{"nonblock", 0, 0, 'N'},
@@ -550,6 +553,9 @@
 				return 1;
 			}
 			break;
+		case 'S':
+			seek_length = atoi(optarg);
+			break;
 		case 'd':
 			timelimit = strtol(optarg, NULL, 0);
 			break;
@@ -2457,6 +2463,8 @@
 	}
 	if (test_au(fd, audiobuf) >= 0) {
 		rhwparams.format = hwparams.format;
+		if (seek_length != 0)
+		        lseek(fd, seek_length, SEEK_SET);
 		pbrec_count = calc_count();
 		playback_go(fd, 0, pbrec_count, FORMAT_AU, name);
 		goto __end;
@@ -2468,17 +2476,23 @@
 		prg_exit(EXIT_FAILURE);;
 	}
 	if ((ofs = test_vocfile(audiobuf)) >= 0) {
+		if (seek_length != 0)
+		        lseek(fd, seek_length, SEEK_SET);
 		pbrec_count = calc_count();
 		voc_play(fd, ofs, name);
 		goto __end;
 	}
 	/* read bytes for WAVE-header */
 	if ((dtawave = test_wavefile(fd, audiobuf, dta)) >= 0) {
+		if (seek_length != 0)
+		        lseek(fd, seek_length, SEEK_SET);
 		pbrec_count = calc_count();
 		playback_go(fd, dtawave, pbrec_count, FORMAT_WAVE, name);
 	} else {
 		/* should be raw data */
 		init_raw_data();
+		if (seek_length != 0)
+		        lseek(fd, seek_length, SEEK_SET);
 		pbrec_count = calc_count();
 		playback_go(fd, dta, pbrec_count, FORMAT_RAW, name);
 	}
--- aplay.1.orig	2011-04-16 02:46:57.000000000 +0200
+++ aplay.1	2011-04-16 02:49:55.000000000 +0200
@@ -77,6 +77,9 @@
 A value of zero means infinity.
 The default is zero, so if this option is omitted then the arecord process will run until it is killed.
 .TP
+\fI\-S, \-\-seek=#\fP
+Seek to position # (in bytes) before starting to play.  This option mostly makes sense on raw files.
+.TP
 \fI\-s, \-\-sleep\-min=#\fP
 Min ticks to sleep. The default is not to sleep.
 .TP

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-- 
(domestic pets only, the antidote for overdose, milk.)
  bloggy blog http://lars.ingebrigtsen.no/

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