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Thanks Patrick, <br>
What you brought up doesn't fix my problem, but does elucidate what's
actually going on. It turns out that there are two problems I'm having:<br>
1) The images are being published independently by two nodes, so they
never have the same timestamp, and thus will never get matched up. Is
there a way to give TimeSynchronizer a threshold so it will match two
message that are close enough?<br>
2) Based on #1, using the raw transport actually shouldn't work. The
reason it currently does is because cvToImgMsg doesn't fill in the
header, so all timestamps are 0. I can manually set the
timestamps/headers before sending off the message, but isn't cv_bridge
supposed to do this?<br>
<br>
Thanks,<br>
-Dan<br>
<br>
On 3/12/10 9:22 PM, Patrick Mihelich wrote:
<blockquote
cite="mid:62051ad91003121922j36f78388we2f8f940f21e4d5@mail.gmail.com"
type="cite">Hi Dan,<br>
<br>
You might need to increase the size of the queues used by the
subscriber filters and/or the synchronizer. If those queues fill up,
messages can get bumped off before they form a complete synchronized
set.<br>
<br>
For debugging purposes it can be useful to register another callback to
the subscriber filters, just so you know when they get any data. I've
attached some sample source code.<br>
<br>
"compressed" transport definitely should work with the time
synchronizer. "theora" will not work reliably because it seems the
plugin doesn't retain the timestamp of the original image. I've opened
a <a moz-do-not-send="true"
href="https://code.ros.org/trac/ros-pkg/ticket/3882">ticket</a> for
that.<br>
<br>
HTH,<br>
Patrick<br>
<br>
<div class="gmail_quote">On Fri, Mar 12, 2010 at 9:12 AM, Dan
Lazewatsky <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:lazewatskyd@cse.wustl.edu">lazewatskyd@cse.wustl.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div bgcolor="#ffffff" text="#000000">Thanks, that did the trick.
One thing I'm still having trouble with is
getting transports other than raw to work with
image_transport::SubscriberFilter. If I pass
image_transport::TransportHints th(transport) to
image_transport::SubscriberFilter, where transport is "compressed" or
"theora", I never seem to get any data. rxgraph -t shows that my node
is connected to my image publisher on the right topic, but the callback
never gets called.<br>
<br>
Thanks,<br>
-Dan
<div>
<div class="h5"><br>
<br>
On 3/11/10 5:11 PM, Patrick Mihelich wrote:
</div>
</div>
<blockquote type="cite">
<div>
<div class="h5">On Thu, Mar 11, 2010 at 2:55 PM, Dan Lazewatsky <span
dir="ltr"><<a moz-do-not-send="true"
href="mailto:lazewatskyd@cse.wustl.edu" target="_blank">lazewatskyd@cse.wustl.edu</a>></span>
wrote:<br>
<div class="gmail_quote">
<blockquote class="gmail_quote"
style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">On
a
related note, is there a way to use TimeSynchronizer with
image_transport rather than subscribing to the image directly?<br>
</blockquote>
<div><br>
Use <a moz-do-not-send="true"
href="http://www.ros.org/doc/api/image_transport/html/classimage__transport_1_1SubscriberFilter.html"
target="_blank">image_transport::SubscriberFilter</a>
as a drop-in replacement for message_filters::Subscriber. It uses an
image_transport subscriber under the hood.<br>
<br>
Cheers,<br>
Patrick<br>
</div>
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