[ecasound] Re: "Active format" in ecasound? (fwd)

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Subject: [ecasound] Re: "Active format" in ecasound? (fwd)
From: Kai Vehmanen (kaiv@wakkanet.fi)
Date: Sat Jun 10 2000 - 15:22:45 EEST

> ecasound -f:s32_le,2,44100 -i tape32-3.wav -f:s16_le,2,44100 -o disc.wav
> and ecasound said it was first switching the active format to
> s32_le,2,44100, then to s16_le,2,44100! Is the default active format
> overriding what I put on the command line? Is ecasound doing its work
> internally in 32 bits, or is it quantizing to 16 bits internally?

Hmm, "default active format" is a bit misleading. Basicly it is only used
when parsing the command-line setup. If no "-f" options are given,
ecasound defaults to "-f:s16_le,2,44100". When it parses the command-line,
this format is used for all audio objects (raw sound files, soundcard,
etc). However, this doesn't apply to formats which contain format info
(wav/aiff/mp3/etc inputs). If you do specify an "-f" option, it applies to
all _following_ audio objects, or until a new "-f" option is given.

When processing, ecasound always uses its internal format (currently
float-32bit, 44100Hz). You can change the internal sampling rate with
-sr:rate option, but sample format is set at compile time. In other words,
all input data is converted to internal format before any processing, and
similarly, before before output, data is converted from internal format to
output format.

So in your example above, the first "-f:" option isn't actually
needed as "tape32-3.wav" knows its format. The second "-f" however
is important. As "disc.wav" is a new file, ecasound has to set the file

Kai Vehmanen <k@eca.cx> ---------------- CS, University of Turku .
 . audio software for linux .. http://www.eca.cx 		 .
 . armchair-tunes mp3/wav/ra . http://www.wakkanet.fi/sculpscape .

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