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Changed PCM intro

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Jaroslav Kysela 2002-02-13 23:19:29 +00:00
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src/pcm/pcm.c
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@ -42,7 +42,32 @@
understanding it as general digital audio processing with volume samples understanding it as general digital audio processing with volume samples
generated in continuous time periods.</P> 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 \section pcm_general_overview General overview