Module Name: src
Committed By: isaki
Date: Sat Mar 26 06:49:27 UTC 2022
Modified Files:
src/sys/dev/audio: audio.c
Log Message:
Add terminology comments.
To generate a diff of this commit:
cvs rdiff -u -r1.119 -r1.120 src/sys/dev/audio/audio.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/audio/audio.c
diff -u src/sys/dev/audio/audio.c:1.119 src/sys/dev/audio/audio.c:1.120
--- src/sys/dev/audio/audio.c:1.119 Sat Mar 26 06:43:36 2022
+++ src/sys/dev/audio/audio.c Sat Mar 26 06:49:27 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: audio.c,v 1.119 2022/03/26 06:43:36 isaki Exp $ */
+/* $NetBSD: audio.c,v 1.120 2022/03/26 06:49:27 isaki Exp $ */
/*-
* Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -63,6 +63,49 @@
*/
/*
+ * Terminology: "sample", "channel", "frame", "block", "track":
+ *
+ * channel frame
+ * | ........
+ * v : : \
+ * +------:------:------:- -+------+ : +------+-.. |
+ * #0(L) |sample|sample|sample| .. |sample| : |sample| |
+ * +------:------:------:- -+------+ : +------+-.. |
+ * #1(R) |sample|sample|sample| .. |sample| : |sample| |
+ * +------:------:------:- -+------+ : +------+-.. | track
+ * : : : : |
+ * +------:------:------:- -+------+ : +------+-.. |
+ * |sample|sample|sample| .. |sample| : |sample| |
+ * +------:------:------:- -+------+ : +------+-.. |
+ * : : /
+ * ........
+ *
+ * \--------------------------------/ \--------..
+ * block
+ *
+ * - A "frame" is the minimum unit in the time axis direction, and consists
+ * of samples for the number of channels.
+ * - A "block" is basic length of processing. The audio layer basically
+ * handles audio data stream block by block, asks underlying hardware to
+ * process them block by block, and then the hardware raises interrupt by
+ * each block.
+ * - A "track" is single completed audio stream.
+ *
+ * For example, the hardware block is assumed to be 10 msec, and your audio
+ * track consists of 2.1(=3) channels 44.1kHz 16bit PCM,
+ *
+ * "channel" = 3
+ * "sample" = 2 [bytes]
+ * "frame" = 2 [bytes/sample] * 3 [channels] = 6 [bytes]
+ * "block" = 44100 [Hz] * (10/1000) [seconds] * 6 [bytes/frame] = 2646 [bytes]
+ *
+ * The terminologies shown here are only for this MI audio layer. Note that
+ * different terminologies may be used in each manufacturer's datasheet, and
+ * each MD driver may follow it. For example, what we call a "block" is
+ * called a "frame" in sys/dev/pci/yds.c.
+ */
+
+/*
* Locking: there are three locks per device.
*
* - sc_lock, provided by the underlying driver. This is an adaptive lock,
@@ -138,7 +181,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.119 2022/03/26 06:43:36 isaki Exp $");
+__KERNEL_RCSID(0, "$NetBSD: audio.c,v 1.120 2022/03/26 06:49:27 isaki Exp $");
#ifdef _KERNEL_OPT
#include "audio.h"
