From d91e0649c94f74451b88beb107adc0fa83f6be05 Mon Sep 17 00:00:00 2001
From: Jaroslav Kysela <perex@perex.cz>
Date: Wed, 13 Feb 2002 23:19:29 +0000
Subject: [PATCH] Changed PCM intro

---
 src/pcm/pcm.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 8132ec59..e7d85a26 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -42,7 +42,32 @@
 understanding it as general digital audio processing with volume samples
 generated in continuous time periods.</P>
 
-<P>Write some description about digital audio here.</P>
+<P>The analog signal is recorded via analog to digital converters (ADC).
+The digital value (de-facto a volume at a specific time) obtained
+from ADC can be further processed. The following picture shows a perfect
+sinus waveform:</P>
+
+<BR>
+\image html wave1.gif
+
+<P>Next image shows digitized representation:</P>
+
+<BR>
+\image html wave2.gif
+
+<P>As you may see, the quality of digital audio signal depends on the time
+(recording rate) and voltage resolution (usually in an linear integer
+representation with basic unit one bit).</P>
+
+<P>The stored digital signal can be converted back to voltage (analog)
+representation via digital to analog converters (DAC).</P>
+
+<P>One digital value is called sample. More samples are collected to frames
+(frame is terminology for ALSA) depending on count of converters used at one
+specific time. One frame might contain one sample (when only one converter is
+used - mono) or more samples (for example: stereo has signals from two converters
+recorded at same time). Digital audio stream contains collection of frames
+recorded at boundaries of continous time periods.</P>
 
 \section pcm_general_overview General overview
 
-- 
2.47.1