diff options
author | Walter Bender <walter@walter-laptop.(none)> | 2009-02-21 12:43:42 (GMT) |
---|---|---|
committer | Walter Bender <walter@walter-laptop.(none)> | 2009-02-21 12:43:42 (GMT) |
commit | 2876869020584497e61a340d4ca3c4c8a8cbde7f (patch) | |
tree | bb83d328a70fa1e8470d954e8ed90d7bba422ae8 /arch_src/pyalsaaudio-0.2/doc/node7.html | |
parent | 9ac3745fbd4253caca810d607a6f230d2b3b341d (diff) |
undoing pyalsaaudio patchv36
Diffstat (limited to 'arch_src/pyalsaaudio-0.2/doc/node7.html')
-rw-r--r-- | arch_src/pyalsaaudio-0.2/doc/node7.html | 169 |
1 files changed, 0 insertions, 169 deletions
diff --git a/arch_src/pyalsaaudio-0.2/doc/node7.html b/arch_src/pyalsaaudio-0.2/doc/node7.html deleted file mode 100644 index f58333a..0000000 --- a/arch_src/pyalsaaudio-0.2/doc/node7.html +++ /dev/null @@ -1,169 +0,0 @@ -<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> -<html> -<head> -<link rel="STYLESHEET" href="pyalsaaudio.css" type='text/css' /> -<link rel="first" href="pyalsaaudio.html" title='PyAlsaAudio' /> -<link rel='contents' href='contents.html' title="Contents" /> -<link rel='last' href='about.html' title='About this document...' /> -<link rel='help' href='about.html' title='About this document...' /> -<link rel="next" href="pcm-objects.html" /> -<link rel="prev" href="module-alsaaudio.html" /> -<link rel="parent" href="module-alsaaudio.html" /> -<link rel="next" href="pcm-objects.html" /> -<meta name='aesop' content='information' /> -<title>4.1 PCM Terminology and Concepts</title> -</head> -<body> -<DIV CLASS="navigation"> -<div id='top-navigation-panel' xml:id='top-navigation-panel'> -<table align="center" width="100%" cellpadding="0" cellspacing="2"> -<tr> -<td class='online-navigation'><a rel="prev" title="4 alsaaudio" - href="module-alsaaudio.html"><img src='previous.png' - border='0' height='32' alt='Previous Page' width='32' /></A></td> -<td class='online-navigation'><a rel="parent" title="4 alsaaudio" - href="module-alsaaudio.html"><img src='up.png' - border='0' height='32' alt='Up One Level' width='32' /></A></td> -<td class='online-navigation'><a rel="next" title="4.2 PCM Objects" - href="pcm-objects.html"><img src='next.png' - border='0' height='32' alt='Next Page' width='32' /></A></td> -<td align="center" width="100%">PyAlsaAudio</td> -<td class='online-navigation'><a rel="contents" title="Table of Contents" - href="contents.html"><img src='contents.png' - border='0' height='32' alt='Contents' width='32' /></A></td> -<td class='online-navigation'><img src='blank.png' - border='0' height='32' alt='' width='32' /></td> -<td class='online-navigation'><img src='blank.png' - border='0' height='32' alt='' width='32' /></td> -</tr></table> -<div class='online-navigation'> -<b class="navlabel">Previous:</b> -<a class="sectref" rel="prev" href="module-alsaaudio.html">4 alsaaudio</A> -<b class="navlabel">Up:</b> -<a class="sectref" rel="parent" href="module-alsaaudio.html">4 alsaaudio</A> -<b class="navlabel">Next:</b> -<a class="sectref" rel="next" href="pcm-objects.html">4.2 PCM Objects</A> -</div> -<hr /></div> -</DIV> -<!--End of Navigation Panel--> - -<H2><A NAME="SECTION002410000000000000000"> -4.1 PCM Terminology and Concepts</A> -</H2> - -<P> -In order to use PCM devices it is useful to be familiar with some concepts and -terminology. - -<P> -<DL> -<DT><STRONG>Sample</STRONG></DT> -<DD>PCM audio, whether it is input or output, consists at the lowest level -of a number of single samples. A sample represents the sound in a single channel in -a brief interval. If more than one channel is in use, more than one sample is required -for each interval to describe the sound. Samples can be of many different sizes, ranging -from 8 bit to 64 bit presition. The specific format of each sample can also vary - they -can be big endian byte order, little endian byte order, or even floats. - -<P> -</DD> -<DT><STRONG>Frame</STRONG></DT> -<DD>A frame consists of exactly one sample per channel. If there is only one -channel (Mono sound) a frame is simply a single sample. If the sound is stereo, each frame -consists of two samples, etc. - -<P> -</DD> -<DT><STRONG>Frame size</STRONG></DT> -<DD>This is the size in bytes of each frame. This can vary a lot: if each sample is -8 bits, and we're handling mono sound, the frame size is one byte. Similarly in 6 channel audio with -64 bit floating point samples, the frame size is 48 bytes - -<P> -</DD> -<DT><STRONG>Rate</STRONG></DT> -<DD>PCM sound consists of a flow of sound frames. The sound rate controls how often -the current frame is replaced. For example, a rate of 8000 Hz means that a new frame is played -or captured 8000 times per second. - -<P> -</DD> -<DT><STRONG>Data rate</STRONG></DT> -<DD>This is the number of bytes, which must be recorded or provided per second -at a certain frame size and rate. - -<P> -8000 Hz mono sound with 8 bit (1 byte) samples has a data rate of 8000 * 1 * 1 = 8 kb/s - -<P> -At the other end of the scale, 96000 Hz, 6 channel sound with 64 bit (8 bytes) samples -has a data rate of 96000 * 6 * 8 = 4608 kb/s (almost 5 Mb sound data per second) - -<P> -</DD> -<DT><STRONG>Period</STRONG></DT> -<DD>When the hardware processes data this is done in chunks of frames. The time interval -between each processing (A/D or D/A conversion) is known as the period. The size of the period has -direct implication on the latency of the sound input or output. For low-latency the period size should -be very small, while low CPU resource usage would usually demand larger period sizes. With ALSA, the -CPU utilization is not impacted much by the period size, since the kernel layer buffers multiple -periods internally, so each period generates an interrupt and a memory copy, but userspace can be -slower and read or write multiple periods at the same time. - -<P> -</DD> -<DT><STRONG>Period size</STRONG></DT> -<DD>This is the size of each period in Hz. <em>Not bytes, but Hz!.</em> In <tt class="module">alsaaudio</tt> -the period size is set directly, and it is therefore important to understand the significance of this -number. If the period size is configured to for example 32, each write should contain exactly 32 frames -of sound data, and each read will return either 32 frames of data or nothing at all. - -<P> -</DD> -</DL> - -<P> -Once you understand these concepts, you will be ready to actually utilize PCM API. Read on. - -<P> - -<DIV CLASS="navigation"> -<div class='online-navigation'> -<p></p><hr /> -<table align="center" width="100%" cellpadding="0" cellspacing="2"> -<tr> -<td class='online-navigation'><a rel="prev" title="4 alsaaudio" - href="module-alsaaudio.html"><img src='previous.png' - border='0' height='32' alt='Previous Page' width='32' /></A></td> -<td class='online-navigation'><a rel="parent" title="4 alsaaudio" - href="module-alsaaudio.html"><img src='up.png' - border='0' height='32' alt='Up One Level' width='32' /></A></td> -<td class='online-navigation'><a rel="next" title="4.2 PCM Objects" - href="pcm-objects.html"><img src='next.png' - border='0' height='32' alt='Next Page' width='32' /></A></td> -<td align="center" width="100%">PyAlsaAudio</td> -<td class='online-navigation'><a rel="contents" title="Table of Contents" - href="contents.html"><img src='contents.png' - border='0' height='32' alt='Contents' width='32' /></A></td> -<td class='online-navigation'><img src='blank.png' - border='0' height='32' alt='' width='32' /></td> -<td class='online-navigation'><img src='blank.png' - border='0' height='32' alt='' width='32' /></td> -</tr></table> -<div class='online-navigation'> -<b class="navlabel">Previous:</b> -<a class="sectref" rel="prev" href="module-alsaaudio.html">4 alsaaudio</A> -<b class="navlabel">Up:</b> -<a class="sectref" rel="parent" href="module-alsaaudio.html">4 alsaaudio</A> -<b class="navlabel">Next:</b> -<a class="sectref" rel="next" href="pcm-objects.html">4.2 PCM Objects</A> -</div> -</div> -<hr /> -<span class="release-info">Release 0.2.</span> -</DIV> -<!--End of Navigation Panel--> - -</BODY> -</HTML> |