16 Dec
2002
16 Dec
'02
12:19 a.m.
Hi, Haakmat,
I'm so glad to see your reply. But I'm still wondering
how I can implement the full duplex operation on sound
card, i.e. playback and record audio on the same card
at same time. I don't think it's a good idea that
reopen the device when switch between reading and
writting, because I found it sometime took much time
to open the device and that means the quality wouldn't
be good. Do u have another solution to it? Anybody
have experience with it ? I really need suggestion
about it and I also believe there must be some tricks
which I havn't understood.
Thanks a lot anyway. This is my first question in this
group and it's my pleasure to get your help.
leo.
--- Pascal Haakmat <a.haakmat(a)chello.nl> wrote:
13/12/02 15:46, leo zhu wrote:
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Hi, guys,
I am working on a project in which I need to
implement
palyback and recording on the same sound card and
in
the same time.
I open the soundcard with RDWR mode and used
'select'
to wait for sound data on card and read it.
After
that, I receive audio data from socket and write
this
data into buffer on card. for now. I tested it
and
i
found if just one way, ie. just read or write,
it
works fine, the quality of sound is fine. but if
two
way, ie. play&record, the sound is horrible
and
the
weird is that I always get better sound quality
from
playback that what i got from recording. (I heard
the
audio from two ends). by the way, I used
SNDCTL_DSP_TRIGGER to syncronyse them.
can this method implement full-duplex functions ?
if
not, what should I do? thanks in advance
Yes, it's possible in principle, and it can work.
Although some
cards/drivers do it better than others... On Linux I
believe the
easiest way is to open the audio device twice: once
for reading and
once for writing. There might be other portability
problems with that
method as well.
I've never gotten SNDCTL_DSP_TRIGGER to work as
expected, but that may just have been impatience.