Reading an shmsink stream from an external application

[Takido]

Hello,

I'm trying to feed an external application which deals sound to a special hardware with shmsink. I read all the doc I could find about shm (including the commented part of shmpipe.h) but I still don't understand they way I could get the audio stream in my external application.

How can I do that ?

Hamza

[Tristan Matthews-2]

2012/7/5 Takido <[hidden email]>:
> Hello,
>
> I'm trying to feed an external application which deals sound to a special
> hardware with shmsink. I read all the doc I could find about shm (including
> the commented part of shmpipe.h) but I still don't understand they way I
> could get the audio stream in my external application.

The easiest route is to use the "shmsrc" element in your external
application, otherwise you will have to write your own shmsrc-like
client for your application.
If it's of any help, a while ago I made a minimal python example using
the shmsrc and shmsink elements that might be of some use:

https://github.com/tmatth/gst-prototypes/tree/master/shm

Best,
Tristan

--
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web: http://tristanswork.blogspot.com
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[Olivier Crête-3]

Hi,

On Thu, 2012-07-05 at 08:52 -0700, Takido wrote:
> Hello,
>
> I'm trying to feed an external application which deals sound to a special
> hardware with shmsink. I read all the doc I could find about shm (including
> the commented part of shmpipe.h) but I still don't understand they way I
> could get the audio stream in my external application.
>
> How can I do that ?

Copy shmpipe.[ch] and shmalloc.[ch] into your application and use the
read API described in shmpipe.h (sp_client_* sp_close, sp_get_fd) to get
the buffers.

--
Olivier Crête
[hidden email]

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[Takido]

Thank you for your answers.

The easiest route is to use the "shmsrc" element in your external
application, otherwise you will have to write your own shmsrc-like
client for your application.
If it's of any help, a while ago I made a minimal python example using
the shmsrc and shmsink elements that might be of some use:

https://github.com/tmatth/gst-prototypes/tree/master/shm

Best,
Tristan

I think I'll be forced to write my own shmsrc-like (actually, if I found a way to directly send my audio stream to the application without shm, I would). Anyway, I'll try to understand your python example which seems interesting.

Copy shmpipe.[ch] and shmalloc.[ch] into your application and use the
read API described in shmpipe.h (sp_client_* sp_close, sp_get_fd) to get
the buffers.

 
I already started to try use this API. So, if I understood well, I have to :

1. Open a client connection with the server : ShmPipe * pipe = sp_client_open(PATH);
   
2. Wait for data to read : select(sp_get_fd(pipe), &rdfs, NULL, NULL, NULL);
   
3. Then receive the data to read : sp_client_recv(pipe, my_buffer);
4. And finally finish to read using : sp_client_recv_finish()

Now it seems very clear to me, however I still can't get it work : even if I send a stream to the specified path (using gst-launch audiotestsrc ! shmsink socket-path=testpath), my little program waits eternally, not seeing any incoming data.

I think I missed something really simple but I can't get it.

 

2012/7/5 Olivier Crête <[hidden email]>

Hi,

On Thu, 2012-07-05 at 08:52 -0700, Takido wrote:
> Hello,
>
> I'm trying to feed an external application which deals sound to a special
> hardware with shmsink. I read all the doc I could find about shm (including
> the commented part of shmpipe.h) but I still don't understand they way I
> could get the audio stream in my external application.
>
> How can I do that ?

Copy shmpipe.[ch] and shmalloc.[ch] into your application and use the
read API described in shmpipe.h (sp_client_* sp_close, sp_get_fd) to get
the buffers.

--
Olivier Crête
[hidden email]

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[Takido]

I finally understood the previous problem, but am now facing another one. Using the following code (which corrects my first problem) :

int fd = sp_get_fd(pipe);

    fd_set rfds;
    FD_ZERO(&rfds);
    FD_SET(fd, &rfds);
    select(fd+1, &rfds, NULL, NULL, NULL);

    int k = recv_to_buffer (pipe, buffer);
    sp_client_recv_finish(pipe, buf);

I get the following error :

shmTest: shmpipe.c:729: sp_client_recv_finish: Assertion `shm_area' failed.
Abandon

Looks like my pipe get no ShmArea, right ? Where could this error come from ?

Thanks.

2012/7/6 Hamza Chouh <[hidden email]>

Thank you for your answers.

The easiest route is to use the "shmsrc" element in your external
application, otherwise you will have to write your own shmsrc-like
client for your application.
If it's of any help, a while ago I made a minimal python example using
the shmsrc and shmsink elements that might be of some use:

https://github.com/tmatth/gst-prototypes/tree/master/shm

Best,
Tristan

I think I'll be forced to write my own shmsrc-like (actually, if I found a way to directly send my audio stream to the application without shm, I would). Anyway, I'll try to understand your python example which seems interesting.

Copy shmpipe.[ch] and shmalloc.[ch] into your application and use the
read API described in shmpipe.h (sp_client_* sp_close, sp_get_fd) to get
the buffers.

 
I already started to try use this API. So, if I understood well, I have to :

1. Open a client connection with the server : ShmPipe * pipe = sp_client_open(PATH);
   
2. Wait for data to read : select(sp_get_fd(pipe), &rdfs, NULL, NULL, NULL);
   
3. Then receive the data to read : sp_client_recv(pipe, my_buffer);
4. And finally finish to read using : sp_client_recv_finish()

Now it seems very clear to me, however I still can't get it work : even if I send a stream to the specified path (using gst-launch audiotestsrc ! shmsink socket-path=testpath), my little program waits eternally, not seeing any incoming data.

I think I missed something really simple but I can't get it.

 

2012/7/5 Olivier Crête <[hidden email]>

Hi,

On Thu, 2012-07-05 at 08:52 -0700, Takido wrote:
> Hello,
>
> I'm trying to feed an external application which deals sound to a special
> hardware with shmsink. I read all the doc I could find about shm (including
> the commented part of shmpipe.h) but I still don't understand they way I
> could get the audio stream in my external application.
>
> How can I do that ?

Copy shmpipe.[ch] and shmalloc.[ch] into your application and use the
read API described in shmpipe.h (sp_client_* sp_close, sp_get_fd) to get
the buffers.

--
Olivier Crête
[hidden email]

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[hidden email]
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[Olivier Crête-3]

On Fri, 2012-07-06 at 11:37 +0200, Hamza Chouh wrote:
> I think I'll be forced to write my own shmsrc-like (actually, if I
> found a way to directly send my audio stream to the application
> without shm, I would).

You can just create a name socket and just use fdsink?

--
Olivier Crête
[hidden email]

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[Todd Fischer]

Date: Fri, 06 Jul 2012 11:03:29 -0700
From: Olivier Cr?te <[hidden email]>
To: [hidden email]
Subject: Re: Reading an shmsink stream from an external application
Message-ID: <1341597809.30902.0.camel@TesterTop4>
Content-Type: text/plain; charset="utf-8"

On Fri, 2012-07-06 at 11:37 +0200, Hamza Chouh wrote:

I think I'll be forced to write my own shmsrc-like (actually, if I

found a way to directly send my audio stream to the application

without shm, I would).

You can just create a name socket and just use fdsink?

You can check out a similar sink, that we called ipcsink.

http://sourceforge.net/apps/mediawiki/freondemo/index.php?title=Gst-ipcsink_plug-in

Todd

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[Takido]

Thanks, I finally solved my problem which was about bad variable initializations.

I have a last question about shmsink : is it possible to get the type of the media that is streamed from the socket created by shmsink ? I mean, the mime type, mono/stereo and stuff like this ?

2012/7/6 Todd Fischer <[hidden email]>

Date: Fri, 06 Jul 2012 11:03:29 -0700
From: Olivier Cr?te <[hidden email]>
To: [hidden email]
Subject: Re: Reading an shmsink stream from an external application
Message-ID: <1341597809.30902.0.camel@TesterTop4>
Content-Type: text/plain; charset="utf-8"

On Fri, 2012-07-06 at 11:37 +0200, Hamza Chouh wrote:

I think I'll be forced to write my own shmsrc-like (actually, if I

found a way to directly send my audio stream to the application

without shm, I would).

You can just create a name socket and just use fdsink?

You can check out a similar sink, that we called ipcsink.

http://sourceforge.net/apps/mediawiki/freondemo/index.php?title=Gst-ipcsink_plug-in

Todd

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