Sun audio device buffering

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2 total messages Started by Dan Frankowski Thu, 19 Nov 1992 19:16

#1810

Author: Dan Frankowski
Date: Thu, 19 Nov 1992 19:16

25 lines
1492 bytes

Sorry to waste bandwidth, but I don't know the proper place to post
this question.

We are using the Sun audio device by opening it (sometimes blocking,
sometimes nonblocking-- it's irrelevant for the question).  We use a
read call:

count = read(record_fd, sound_bytes_ptr, sound_bytes_left);

where record_fd is the file descriptor of the sound device opened
for recording, sound_bytes_ptr is a pointer to the 0th element of
an array of chars, and sound_bytes_left is usually 800.

The very first call seems to return a small number of bytes (5 or 6).
After that, it always returns data in multiples of 1K.  I read the
audio man pages, looked in Sun documentation, tried fstat(), and I
just cannot seem to find why the device returns chunks in multiples of
1K.  It is important to us to be able to get smaller chunks.  Does
anyone know how to do this?

Thanks for your time.

Dan
--
Dan Frankowski                dfrankow@cs.umn.edu

Re: Sun audio device buffering

#1813

Author: Dan Frankowski
Date: Thu, 19 Nov 1992 23:06

19 lines
1189 bytes

In <dfrankow.722200575@peca> dfrankow@peca.cs.umn.edu (Dan Frankowski) writes:

>Sorry to waste bandwidth, but I don't know the proper place to post
>this question.

>count = read(record_fd, sound_bytes_ptr, sound_bytes_left);

>.. and sound_bytes_left is usually 800.

Argh!  Typo!  s_b_l is usually 8000.  This is essentially the call:

count = read(fd, buf, 8000);

Sometimes it gives less than 8000.  No problem, since it only has the
sound since I last asked it.  The problem is that it only gives me
1024 bytes, or 2048, or 3072, or 4096, etc.  It holds anything less
than 1K to itself.  I want to get all the data, even if it's less than 1K.

Dan

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