[ros-users] Nodelet version of rosbag?

[Patrick Bouffard]

For a nodelet rosbag, wouldn't the message be passed to rosbag as a
const pointer first, and then rosbag itself would handle
serialization? Or is that even possible.. maybe not, I guess rosbag
doesn't just magically know how to serialize each and every message
type--or does it?

Pat

On Sun, Jan 30, 2011 at 12:21 PM, Brian Gerkey <gerkey at willowgarage.com> wrote:
> On Sun, Jan 30, 2011 at 11:47 AM, Radu Bogdan Rusu
> <rusu at willowgarage.com> wrote:
>> We could try creating a BAGWriter class similar to pcl_ros::BAGReader if you think that's useful. Basically you want to
>> dump data to disk faster, without going through serialization/deserialization, right?
>
> I'm pretty sure that rosbag doesn't deserialize anything, but rather
> just dumps serialized messages to disk as fast as it can.   And
> because the .bag format is serialized messages, you can't avoid the
> serialization step.  I think that the nodelet method would only save
> the (kernel-mediated) copy of each serialized message from the
> producing node to rosbag.  From the point of view of throughput, I
> would expect writing to disk to be the rate-limiting step.   I guess
> it comes down to whether the CPU usage involved the node->rosbag copy
> is significant.
>
>        brian.
>
>> On 01/30/2011 11:31 AM, Patrick Bouffard wrote:
>>> Are there any plans to implement rosbag (in particular, rosbag record)
>>> as a nodelet? I can see this being useful when you want to record
>>> large amounts of camera or point cloud data.
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