16 May
2016
16 May
'16
11:44 p.m.
I've been knocking my head against a wall for more
than a year trying to
figure out how to correctly mix two streams of audio while using
libsndfile for input and libao for output. My main requirement is that
I cannot assume anything about the output drivers -- that is, I cannot
depend on the output driver (ALSA, OSS, Sun, etc) being able to do the
mixing for me. Many of my target platforms lack any sort of mixing
services. I need to do this myself. I tried starting a mixer/player
thread that would work in a producer/consumer relationship with one or
two audio file decoder threads. I can play one sound at a time just
fine. When I try to do both, I get distortion followed by a segfault.
Hi,
not sure if I understood correctly: do you just want to mix N files?
Like you I'm learning libsndfile and libao so this is my attempt to mix
some audio files:
http://pastebin.com/dm7z8b3Z
HTH,
Andrea
P.S.
Can someone explain line 88 (I already read the sndfile FAQ)?
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---------- Forwarded message ----------
From: Andrea Del Signore <sejerpz(a)gmail.com>
To: linux-audio-dev(a)lists.linuxaudio.org
Cc:
Date: Mon, 16 May 2016 21:26:40 +0000 (UTC)
Subject: Re: [LAD] mixing while using libao and libsndfile
On Sun, 15 May 2016 16:34:34 +0000, David Griffith wrote:
I've been knocking my head against a wall for
more than a year trying to
figure out how to correctly mix two streams of audio while using
libsndfile for input and libao for output. My main requirement is that
I cannot assume anything about the output drivers -- that is, I cannot
depend on the output driver (ALSA, OSS, Sun, etc) being able to do the
mixing for me. Many of my target platforms lack any sort of mixing
services. I need to do this myself. I tried starting a mixer/player
thread that would work in a producer/consumer relationship with one or
two audio file decoder threads. I can play one sound at a time just
fine. When I try to do both, I get distortion followed by a segfault.
So, I'm back to a demo program. What must I do to this program to cause
it to start playing one audio file, then play another N seconds later?
David Griffith dave(a)661.org
Hi,
not sure if I understood correctly: do you just want to mix N files?
I'm a noob with both libsndfile and libao :)
Here my code: http://pastebin.com/dm7z8b3Z
HTH,
Andrea
P.S.
Can someone explain line 88 (I already read the sndfile FAQ)?
17 May
17 May
12:25 a.m.
New subject: [LAD] mixing while using libao and libsndfile
On Mon, 16 May 2016, Andrea Del Signore wrote:
I'm not simply trying to mix two files. My main project is a game engine
in which two sounds are allowed at any one time. For instance, there can
be constant background music punctuated by sound effects. I can't get
these to mix correctly.
Regarding your line 88, I had trouble with this too:
sf_count_t item_read = sf_read_float (sndfile[i], filebuffer, BUFFSIZE);
// WHY BUFFSIZE? Shouldn't be BUFFSIZE * channels?
The third parameter is for the number of items or frames. A frame is made
up of one sample per channel. Earlier you set up filebuffer like this:
buflen = BUFFSIZE * sf_info[0].channels;
filebuffer = malloc(buflen * sizeof(float));
The size of filebuffer is BUFFSIZE float-sized frames. Therefore when you
specify BUFFSIZE as the number of floats to read, they all fit in
filebuffer.
--
David Griffith
dave(a)661.org
I've been
knocking my head against a wall for more than a year trying to
figure out how to correctly mix two streams of audio while using
libsndfile for input and libao for output. My main requirement is that
I cannot assume anything about the output drivers -- that is, I cannot
depend on the output driver (ALSA, OSS, Sun, etc) being able to do the
mixing for me. Many of my target platforms lack any sort of mixing
services. I need to do this myself. I tried starting a mixer/player
thread that would work in a producer/consumer relationship with one or
two audio file decoder threads. I can play one sound at a time just
fine. When I try to do both, I get distortion followed by a segfault.
Hi,
not sure if I understood correctly: do you just want to mix N files?
Like you I'm learning libsndfile and libao so this is my attempt to mix some audio
files:
http://pastebin.com/dm7z8b3Z
HTH,
Andrea
P.S.
Can someone explain line 88 (I already read the sndfile FAQ)?
2:50 a.m.
New subject: [LAD] mixing while using libao and libsndfile
On May 16, 2016 3:25:48 PM PDT, David Griffith <dave(a)661.org> wrote:
Earlier you set up filebuffer like this:
buflen = BUFFSIZE * sf_info[0].channels;
filebuffer = malloc(buflen * sizeof(float));
The size of filebuffer is BUFFSIZE float-sized frames. Therefore when
you
specify BUFFSIZE as the number of floats to read, they all fit in
filebuffer.
Sorry. I meant BUFFSIZE as the number of /frames/.
--
David Griffith
dave(a)661.org
7:42 a.m.
New subject: [LAD] mixing while using libao and libsndfile
On Mon, 16 May 2016 17:50:24 -0700, David Griffith wrote:
On May 16, 2016 3:25:48 PM PDT, David Griffith
<dave(a)661.org> wrote:
Yes, but if I understand correctly when using sf_read_* functions,
sndfile expect the number of items as the third parameters and NOT the
number of frames.
As per FAQ a frame is 1 item per channel, so I expect BUFFSIZE * channels
to be the correct value to pass, but it doesn't work!?
Ciao,
Andrea
Earlier you set up filebuffer like this:
buflen = BUFFSIZE * sf_info[0].channels;
filebuffer = malloc(buflen * sizeof(float));
The size of filebuffer is BUFFSIZE float-sized frames. Therefore when
you specify BUFFSIZE as the number of floats to read, they all fit in
filebuffer.
Sorry. I meant BUFFSIZE as the number of /frames/.
7:32 a.m.
New subject: [LAD] mixing while using libao and libsndfile
On Tue, May 17, 2016 at 12:25 AM, David Griffith <dave(a)661.org> wrote:
On Mon, 16 May 2016, Andrea Del Signore wrote:
Hi,
in that case you can just skip the right number of frames before starting
playing sounds.
I modified my code to take the start time for each file and schedule the
play time with frame accuracy.
http://pastebin.com/0PMyfPvK
If you want your timing to be sample accurate the algorithm is a bit more
complex.
Ciao,
Andrea
I've been knocking my head against a wall for
more than a year trying to
I'm not simply trying to mix two files. My main project is a game engine
in which two sounds are allowed at any one time. For instance, there can
be constant background music punctuated by sound effects. I can't get
these to mix correctly.
figure out how to correctly mix two streams of
audio while using
libsndfile for input and libao for output. My main requirement is that
I cannot assume anything about the output drivers -- that is, I cannot
depend on the output driver (ALSA, OSS, Sun, etc) being able to do the
mixing for me. Many of my target platforms lack any sort of mixing
services. I need to do this myself. I tried starting a mixer/player
thread that would work in a producer/consumer relationship with one or
two audio file decoder threads. I can play one sound at a time just
fine. When I try to do both, I get distortion followed by a segfault.
Hi,
not sure if I understood correctly: do you just want to mix N files?
Like you I'm learning libsndfile and libao so this is my attempt to mix
some audio files:
http://pastebin.com/dm7z8b3Z
HTH,
Andrea
P.S.
Can someone explain line 88 (I already read the sndfile FAQ)?
10:26 a.m.
New subject: [LAD] mixing while using libao and libsndfile
On Tue, 17 May 2016, Andrea Del Signore wrote:
On Tue, May 17, 2016 at 12:25 AM, David Griffith
<dave(a)661.org> wrote:
On Mon, 16 May 2016, Andrea Del Signore wrote:
That won't work. Your code schedules things ahead of time before anything
else happens. I need to be able to fire off sound effects the instant the
player does something to cause them. I can't know in advance.
--
David Griffith
dave(a)661.org
I'm not simply trying to mix two files. My
main project is a
game engine in which two sounds are allowed at any one time.
For instance, there can be constant background music punctuated
by sound effects. I can't get these to mix correctly.
Hi,
in that case you can just skip the right number of frames before starting
playing sounds.
I modified my code to take the start time for each file and schedule the
play time with frame accuracy.
http://pastebin.com/0PMyfPvK
If you want your timing to be sample accurate the algorithm is a bit more
complex.
10:50 a.m.
New subject: [LAD] mixing while using libao and libsndfile
On Tue, May 17, 2016 at 10:26 AM, David Griffith <dave(a)661.org> wrote:
On Tue, 17 May 2016, Andrea Del Signore wrote:
On Tue, May 17, 2016 at 12:25 AM, David Griffith <dave(a)661.org> wrote:
Yes my code for now implements only your initial request (play 2 sounds
spaced by few seconds), and it shows how to schedule N sound files of
different length at different times.
I'll try to write a simple mixer for my next learning exercise :)
Have a good day,
Andrea
On Mon, 16 May 2016, Andrea Del Signore wrote:
That won't work. Your code schedules things ahead of time before anything
else happens. I need to be able to fire off sound effects the instant the
player does something to cause them. I can't know in advance.
--
David Griffith
dave(a)661.org I'm not simply trying to mix two files. My
main project is a
game engine in which two sounds are allowed at any one time.
For instance, there can be constant background music punctuated
by sound effects. I can't get these to mix correctly.
Hi,
in that case you can just skip the right number of frames before starting
playing sounds.
I modified my code to take the start time for each file and schedule the
play time with frame accuracy.
http://pastebin.com/0PMyfPvK
If you want your timing to be sample accurate the algorithm is a bit more
complex.
2:08 p.m.
New subject: [LAD] mixing while using libao and libsndfile
Your design is way too simple and fundamentally wrong.
If you want low latency you need to use a pull model (aka callback model)
for audio i/o to the device. Let the device tell you when it wants audio
data, and deliver it,on time, without blocking (which means no on-demand
file i/o in the same thread as the device audio i/o). See
http://www.rossbencina.com/code/real-time-audio-programming-101-time-waits-…
On Tue, May 17, 2016 at 4:26 AM, David Griffith <dave(a)661.org> wrote:
On Tue, 17 May 2016, Andrea Del Signore wrote:
On Tue, May 17, 2016 at 12:25 AM, David Griffith <dave(a)661.org> wrote:
On Mon, 16 May 2016, Andrea Del Signore wrote:
That won't work. Your code schedules things ahead of time before anything
else happens. I need to be able to fire off sound effects the instant the
player does something to cause them. I can't know in advance.
--
David Griffith
dave(a)661.org
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Linux-audio-dev(a)lists.linuxaudio.org
http://lists.linuxaudio.org/listinfo/linux-audio-dev
I'm not simply trying to mix two files. My
main project is a
game engine in which two sounds are allowed at any one time.
For instance, there can be constant background music punctuated
by sound effects. I can't get these to mix correctly.
Hi,
in that case you can just skip the right number of frames before starting
playing sounds.
I modified my code to take the start time for each file and schedule the
play time with frame accuracy.
http://pastebin.com/0PMyfPvK
If you want your timing to be sample accurate the algorithm is a bit more
complex.
2:18 p.m.
New subject: [LAD] mixing while using libao and libsndfile
On Tue, 17 May 2016 08:08:00 -0400, Paul Davis wrote:
Hi Paul,
thanks for your input! I'm aware of "most" of the design issues of that
code. It's only an example that I've done to understand basic libsndfile
api (or just an excuse to write something fun in C ;) )
My next version will be better, but it will mantains the push model in
the api, in order to keep things very simple.
Thanks again,
Andrea
Your design is way too simple and fundamentally wrong.
If you want low latency you need to use a pull model (aka callback
model)
for audio i/o to the device. Let the device tell you when it wants audio
data, and deliver it,on time, without blocking (which means no on-demand
file i/o in the same thread as the device audio i/o). See
http://www.rossbencina.com/code/real-time-audio-programming-101-time-
waits-for-nothing
10:23 p.m.
New subject: [LAD] mixing while using libao and libsndfile
On Tue, 17 May 2016 08:26:17 +0000, David Griffith wrote:
On Tue, 17 May 2016, Andrea Del Signore wrote:
Hi,
another code iteraction: http://pastebin.com/v8gTWBtJ
This is a basic implementation, there is a lot of things left todo (RT
safeness as Paul already noted, code cleanup, etc...)
HTH,
Andrea
P.S.
I don't code in C very often, may be this is my first time in 6 or 7
years. For me this code snippet is just an excuse to do some exercise :)
On Tue, May 17, 2016 at 12:25 AM, David Griffith
<dave(a)661.org> wrote:
On Mon, 16 May 2016, Andrea Del Signore wrote:
That won't work. Your code schedules things ahead of time before
anything else happens. I need to be able to fire off sound effects the
instant the player does something to cause them. I can't know in
advance. I'm not simply trying to mix two files. My
main project is a game
engine in which two sounds are allowed at any one time. For instance,
there can be constant background music punctuated by sound effects.
I can't get these to mix correctly.
Hi,
in that case you can just skip the right number of frames before
starting playing sounds.
I modified my code to take the start time for each file and schedule
the play time with frame accuracy.
http://pastebin.com/0PMyfPvK
If you want your timing to be sample accurate the algorithm is a bit
more complex.
3544
days inactive
3545
days old
linux-audio-dev@lists.linuxaudio.org
9 comments
3 participants
participants (3)
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Andrea Del Signore -
David Griffith -
Paul Davis