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author | Guido van Rossum <guido@python.org> | 1995-03-13 10:03:32 (GMT) |
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committer | Guido van Rossum <guido@python.org> | 1995-03-13 10:03:32 (GMT) |
commit | 6bb1adc7ee688be85b839b747cf25a9e6254cc22 (patch) | |
tree | 8cb910de69fa0322275e60763bfc93a1ea12386f /Doc/libaudioop.tex | |
parent | a8a8d4aadd49e3776e2212318331105c939974b4 (diff) | |
download | cpython-6bb1adc7ee688be85b839b747cf25a9e6254cc22.zip cpython-6bb1adc7ee688be85b839b747cf25a9e6254cc22.tar.gz cpython-6bb1adc7ee688be85b839b747cf25a9e6254cc22.tar.bz2 |
small changes by Soren Larsen
Diffstat (limited to 'Doc/libaudioop.tex')
-rw-r--r-- | Doc/libaudioop.tex | 56 |
1 files changed, 25 insertions, 31 deletions
diff --git a/Doc/libaudioop.tex b/Doc/libaudioop.tex index 61ab7fc..03e074d 100644 --- a/Doc/libaudioop.tex +++ b/Doc/libaudioop.tex @@ -1,8 +1,8 @@ \section{Built-in module \sectcode{audioop}} \bimodindex{audioop} -The audioop module contains some useful operations on sound fragments. -It operates on sound fragments consisting of signed integer samples of +The \code{audioop} module contains some useful operations on sound fragments. +It operates on sound fragments consisting of signed integer samples 8, 16 or 32 bits wide, stored in Python strings. This is the same format as used by the \code{al} and \code{sunaudiodev} modules. All scalar items are integers, unless specified otherwise. @@ -19,7 +19,7 @@ per sample, etc. \end{excdesc} \begin{funcdesc}{add}{fragment1\, fragment2\, width} -This function returns a fragment that is the addition of the two samples +This function returns a fragment which is the addition of the two samples passed as parameters. \var{width} is the sample width in bytes, either \code{1}, \code{2} or \code{4}. Both fragments should have the same length. \end{funcdesc} @@ -60,8 +60,8 @@ passed as an argument. \begin{funcdesc}{findfactor}{fragment\, reference} This routine (which only accepts 2-byte sample fragments) calculates a factor \var{F} such that \code{rms(add(fragment, mul(reference, -F)))} -is minimal, i.e. it calculates the factor with which you should -multiply \var{reference} to make it match as good as possible to +is minimal, i.e.\ it calculates the factor with which you should +multiply \var{reference} to make it match as well as possible to \var{fragment}. The fragments should be the same size. The time taken by this routine is proportional to \code{len(fragment)}. @@ -69,7 +69,7 @@ The time taken by this routine is proportional to \code{len(fragment)}. \begin{funcdesc}{findfit}{fragment\, reference} This routine (which only accepts 2-byte sample fragments) tries to -match \var{reference} as good as possible to a portion of +match \var{reference} as well as possible to a portion of \var{fragment} (which should be the longer fragment). It (conceptually) does this by taking slices out of \var{fragment}, using \code{findfactor} to compute the best match, and minimizing the @@ -81,8 +81,8 @@ and \var{factor} the floating-point factor as per \code{findfactor}. \begin{funcdesc}{findmax}{fragment\, length} This routine (which only accepts 2-byte sample fragments) searches -\var{fragment} for a slice of length \var{length} samples (not bytes!) -with maximum energy, i.e. it returns \var{i} for which +\var{fragment} for a slice of length \var{length} samples (not bytes!)\ +with maximum energy, i.e.\ it returns \var{i} for which \code{rms(fragment[i*2:(i+length)*2])} is maximal. The routine takes time proportional to \code{len(fragment)}. @@ -140,7 +140,7 @@ This function returns the maximum peak-peak value in the sound fragment. \end{funcdesc} \begin{funcdesc}{mul}{fragment\, width\, factor} -Mul returns a fragment that has all samples in the original framgent +Return a fragment that has all samples in the original framgent multiplied by the floating-point value \var{factor}. Overflow is silently ignored. \end{funcdesc} @@ -150,25 +150,6 @@ This function reverses the samples in a fragment and returns the modified fragment. \end{funcdesc} -\begin{funcdesc}{tomono}{fragment\, width\, lfactor\, rfactor} -This function converts a stereo fragment to a mono fragment. The left -channel is multiplied by \var{lfactor} and the right channel by -\var{rfactor} before adding the two channels to give a mono signal. -\end{funcdesc} - -\begin{funcdesc}{tostereo}{fragment\, width\, lfactor\, rfactor} -This function generates a stereo fragment from a mono fragment. Each -pair of samples in the stereo fragment are computed from the mono -sample, whereby left channel samples are multiplied by \var{lfactor} -and right channel samples by \var{rfactor}. -\end{funcdesc} - -\begin{funcdesc}{mul}{fragment\, width\, factor} -Mul returns a fragment that has all samples in the original framgent -multiplied by the floating-point value \var{factor}. Overflow is -silently ignored. -\end{funcdesc} - \begin{funcdesc}{rms}{fragment\, width\, factor} Returns the root-mean-square of the fragment, i.e. \iftexi @@ -184,6 +165,19 @@ divided by the sumber of samples. This is a measure of the power in an audio signal. \end{funcdesc} +\begin{funcdesc}{tomono}{fragment\, width\, lfactor\, rfactor} +This function converts a stereo fragment to a mono fragment. The left +channel is multiplied by \var{lfactor} and the right channel by +\var{rfactor} before adding the two channels to give a mono signal. +\end{funcdesc} + +\begin{funcdesc}{tostereo}{fragment\, width\, lfactor\, rfactor} +This function generates a stereo fragment from a mono fragment. Each +pair of samples in the stereo fragment are computed from the mono +sample, whereby left channel samples are multiplied by \var{lfactor} +and right channel samples by \var{rfactor}. +\end{funcdesc} + \begin{funcdesc}{ulaw2lin}{fragment\, width} This function converts sound fragments in ULAW encoding to linearly encoded sound fragments. ULAW encoding always uses 8 bits samples, so @@ -191,7 +185,7 @@ encoded sound fragments. ULAW encoding always uses 8 bits samples, so \end{funcdesc} Note that operations such as \code{mul} or \code{max} make no -distinction between mono and stereo fragments, i.e. all samples are +distinction between mono and stereo fragments, i.e.\ all samples are treated equal. If this is a problem the stereo fragment should be split into two mono fragments first and recombined later. Here is an example of how to do that: @@ -207,10 +201,10 @@ def mul_stereo(sample, width, lfactor, rfactor): \end{verbatim}\ecode If you use the ADPCM coder to build network packets and you want your -protocol to be stateless (i.e. to be able to tolerate packet loss) +protocol to be stateless (i.e.\ to be able to tolerate packet loss) you should not only transmit the data but also the state. Note that you should send the \var{initial} state (the one you passed to -lin2adpcm) along to the decoder, not the final state (as returned by +\code{lin2adpcm}) along to the decoder, not the final state (as returned by the coder). If you want to use \code{struct} to store the state in binary you can code the first element (the predicted value) in 16 bits and the second (the delta index) in 8. |