Gstreamer e DCCP: issues related to ccid-3

Gstreamer e DCCP: issues related to ccid-3

[Łeandro Sales]

Can you please revise to me the problem that you and the VLC guy had
while was implement DCCP support on VLC?
   I'm implementing the dccp plugin for gstreamer and everything goes
very well, I can transmit an mp3 sound using ccid-2, but when I try to
use ccid-3, I can just send very little via send function and after
the function returns 11 (EAGAIN). Is there any different parameter
that I should set? I think that the problem that you had in VLC should
be the same for me and in this case you help me. I have been working
with Arnaldo on this stuffs but I decided to make it public sharing
this problem to all of you and get some help.
   Basically the functions that I'm using to send are the following:

PS: the second function, gst_dccp_send_buffer, is a call back function
called by gstreamer when it has data to be sent. Thank you.

/* write buffer to given socket incrementally.
 * Returns number of bytes written.
 */
gint
gst_dccp_socket_write (int socket, const void *buf, size_t count)
{
 size_t bytes_written = 0;
 ssize_t wrote;

 while (bytes_written < count) {
   wrote = send (socket, (const char *) buf + bytes_written,
           count - bytes_written, MSG_NOSIGNAL);
   if (wrote <= 0) {
     return bytes_written;
   }
   bytes_written += wrote;
 }

 if (bytes_written < 0)
   GST_WARNING ("error while writing");
 else
   GST_LOG ("wrote %" G_GSIZE_FORMAT " bytes succesfully", bytes_written);
 return bytes_written;
}


/* write a GDP header to the socket.  Return false if fails. */
GstFlowReturn
gst_dccp_send_buffer (GstElement * this, GstBuffer * buffer, int socket)
{
 size_t wrote;

 gint size = 0;
 guint8 *data;

 size = GST_BUFFER_SIZE (buffer);
 data = GST_BUFFER_DATA (buffer);

 GST_LOG_OBJECT (this, "writing %d bytes for GDP buffer header\n", size);
 printf("writing %d bytes for GDP buffer header\n\n", size);
 wrote = gst_dccp_socket_write (socket, data, size);
 //g_free (data);

 if (wrote != size) {
   GST_ELEMENT_ERROR (this, CORE, TOO_LAZY, (NULL),
       ("Error while sending data"));
   printf("Error while sending data\n");
   return GST_FLOW_ERROR;
 }

 return GST_FLOW_OK;
}

Re: Gstreamer e DCCP: issues related to ccid-3

[Gerrit Renker]

|   I'm implementing the dccp plugin for gstreamer and everything goes
|  very well, I can transmit an mp3 sound using ccid-2, but when I try to
|  use ccid-3, I can just send very little via send function and after
|  the function returns 11 (EAGAIN). Is there any different parameter
|  that I should set? I think that the problem that you had in VLC should
|  be the same
This problem (or "feature") is well-known, Ian has also repeatedly pointed out
to this. Basically, what your code needs to be able to do is cope with EAGAIN,
i.e. when the TX buffer is full and CCID3 decides to throttle the sending speed,
the write call needs to be repeated.

I haven't checked the VLC code lately (it will have such a test), but I know that 
Andre Noll developed a very clever way of handling this, by using a "generic chunk queue" 
for audio chunks which could currently not be sent. He implemented this in paraslash
(file dccp_send.c), the sources are on http://www.systemlinux.org/~maan/paraslash/

For this most recent feature, it is best to use his git tarball:

  http://www.systemlinux.org/~maan/paraslash/versions/paraslash-git.tar.bz2


I also 

Re: Gstreamer e DCCP: issues related to ccid-3

[Gerrit Renker]

|  Basically the functions that I'm using to send are the following:
|  
|  PS: the second function, gst_dccp_send_buffer, is a call back function
|  called by gstreamer when it has data to be sent. Thank you.
  
|  /* write buffer to given socket incrementally.
|   * Returns number of bytes written.
|   */
|  gint
|  gst_dccp_socket_write (int socket, const void *buf, size_t count)
|  {
|   size_t bytes_written = 0;
|   ssize_t wrote;
|  
|   while (bytes_written < count) {
|     wrote = send (socket, (const char *) buf + bytes_written,
|             count - bytes_written, MSG_NOSIGNAL);
|     if (wrote <= 0) {
|       return bytes_written;
|     }
|     bytes_written += wrote;
|   }
/* something like (but do have a look at the paraslash sources)
    do {
	wrote = send (socket, (const char *) buf + bytes_written,
                             count - bytes_written, MSG_NOSIGNAL);
    }  while (wrote < 0 && errno = EAGAIN);
*/


If the function below is a callback, then this may be tricky, since
the solution is to poll (the above do..while loop), until there is 
room in the sender's TX queue.
In principle, you could use the same do..while loop, or decide to
store the chunk back into a list and reschedule the callback to
"call later", as it is done in the paraslash sources.
 
|  
|  /* write a GDP header to the socket.  Return false if fails. */
|  GstFlowReturn
|  gst_dccp_send_buffer (GstElement * this, GstBuffer * buffer, int socket)
|  {
|   size_t wrote;
|  
|   gint size = 0;
|   guint8 *data;
|  
|   size = GST_BUFFER_SIZE (buffer);
|   data = GST_BUFFER_DATA (buffer);
|  
|   GST_LOG_OBJECT (this, "writing %d bytes for GDP buffer header\n", size);
|   printf("writing %d bytes for GDP buffer header\n\n", size);
|   wrote = gst_dccp_socket_write (socket, data, size);
|   //g_free (data);
|  
|   if (wrote != size) {
|     GST_ELEMENT_ERROR (this, CORE, TOO_LAZY, (NULL),
|         ("Error while sending data"));
|     printf("Error while sending data\n");
|     return GST_FLOW_ERROR;
|   }
|  
|   return GST_FLOW_OK;
|  }
|  

Re: Gstreamer e DCCP: issues related to ccid-3

[Ian McDonald]

On 10/25/07, Gerrit Renker <gerrit@erg.abdn.ac.uk> wrote:
> /* something like (but do have a look at the paraslash sources)
>     do {
>         wrote = send (socket, (const char *) buf + bytes_written,
>                              count - bytes_written, MSG_NOSIGNAL);
>     }  while (wrote < 0 && errno = EAGAIN);
> */
>
>
You can also look at iperf code, ttcp code etc.
-- 
Web1: http://wand.net.nz/~iam4/
Web2: http://www.jandi.co.nz
Blog: http://iansblog.jandi.co.nz

Re: Gstreamer e DCCP: issues related to ccid-3

[Łeandro Sales]

2007/10/25, Ian McDonald <ian.mcdonald@jandi.co.nz>:
> On 10/25/07, Gerrit Renker <gerrit@erg.abdn.ac.uk> wrote:
> > /* something like (but do have a look at the paraslash sources)
> >     do {
> >         wrote = send (socket, (const char *) buf + bytes_written,
> >                              count - bytes_written, MSG_NOSIGNAL);
> >     }  while (wrote < 0 && errno = EAGAIN);
> > */
> >
> >
> You can also look at iperf code, ttcp code etc.
> --
> Web1: http://wand.net.nz/~iam4/
> Web2: http://www.jandi.co.nz
> Blog: http://iansblog.jandi.co.nz
>

Did you implemented a similar solution in the code that you sent to
me? I didn't have enough time to check your code because I was busy on
the ccid-4 patches.

Leandro.

Re: Gstreamer e DCCP: issues related to ccid-3

[Gerrit Renker]

Quoting Łeandro Sales:
|  2007/10/25, Ian McDonald <ian.mcdonald@jandi.co.nz>:
|  > On 10/25/07, Gerrit Renker <gerrit@erg.abdn.ac.uk> wrote:
|  > > /* something like (but do have a look at the paraslash sources)
|  > >     do {
|  > >         wrote = send (socket, (const char *) buf + bytes_written,
|  > >                              count - bytes_written, MSG_NOSIGNAL);
|  > >     }  while (wrote < 0 && errno = EAGAIN);
|  > > */
|  > >
|  > >
|  > You can also look at iperf code, ttcp code etc.
|  > --
|  > Web1: http://wand.net.nz/~iam4/
|  > Web2: http://www.jandi.co.nz
|  > Blog: http://iansblog.jandi.co.nz
|  >
|  
|  Did you implemented a similar solution in the code that you sent to
|  me? I didn't have enough time to check your code because I was busy on
|  the ccid-4 patches.
|  
Check
	* ttcp (all versions, Arnaldo's, Ian's, or mine)
	* iperf http://www.erg.abdn.ac.uk/users/gerrit/dccp/apps/#iperf
	* but most of all: paraslash
		- http://www.systemlinux.org/~maan/paraslash/
		- get http://www.systemlinux.org/~maan/paraslash/versions/paraslash-git.tar.bz2
-
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