Are these expected behavior of rosbag?
**Behavior-1**
$ wget http://download.ros.org/data/rosbag/clock_alive.bag
$ rosbag info clock_alive.bag
path: clock_alive.bag
version: 2.0
duration: 40.0s
start: Jun 03 2015 05:27:52.30 (1433334472.30)
end: Jun 03 2015 05:28:32.29 (1433334512.29)
size: 14.5 MB
messages: 40000
compression: bz2 [40000/40000 chunks; 0.01%]
uncompressed: 55.9 GB @ 1.4 GB/s
compressed: 5.7 MB @ 145.5 KB/s (0.01%)
types: std_msgs/String [992ce8a1687cec8c8bd883ec73ca41d1]
topics: /blabla 40000 msgs : std_msgs/String
$ rosbag play -l --clock clock_alive.bag
[RUNNING] Bag Time: 1433334474.755216 Duration: 2.453124 / 39.990000
The time elapses as expected. Then on another terminal,
$ rostopic hz /blabla
subscribed to [/blabla]
WARNING: may be using simulated time
average rate: 0.000
min: 0.000s max: 0.000s std dev: 0.00000s window: 59
no new messages
no new messages
no new messages
no new messages
no new messages
no new messages
Issues are 1) the topic `/blabla` is being published throughout the entire bag file as you see the screenshot from rqt_bag below, but `rostopic` is capturing only occasionally as above, 2) `Bag time` pauses elapsing. Once `rostopic` command gets terminated it resumes without jump (i.e. Bag time was paused).
**Behavior-2**
Then setting false to `/use_sim_time`,
term-1$ rosbag play clock_alive.bag
term-2$ rostopic hz /blabla
subscribed to [/blabla]
average rate: 804.263
min: 0.001s max: 0.005s std dev: 0.00109s window: 12
average rate: 22.330
min: 0.001s max: 1.040s std dev: 0.18831s window: 35
average rate: 26.260
min: 0.001s max: 1.040s std dev: 0.15480s window: 59
average rate: 19.355
min: 0.001s max: 1.040s std dev: 0.19223s window: 63
average rate: 24.224
min: 0.001s max: 1.040s std dev: 0.16041s window: 106
average rate: 30.743
min: 0.001s max: 1.040s std dev: 0.14531s window: 165
This time it looks much like as expected. But still "Bag time" pauses while rostopic runs.
Particularly in my case, I'm writing tests using .bag files so `use_sim_time` is really in need.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty
$ more /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 60
model name : Intel(R) Core(TM) i7-4710MQ CPU @ 2.50GHz
stepping : 3
microcode : 0x17
cpu MHz : 3356.250
cache size : 6144 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
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