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This is perfectly understandable. You have 300Mb in 2:18s, i.e. ~138Mb/s to achieve real-time. It is likely to be more that your hard-drive maximum bandwidth even if you consider that you are the only process accessing to the disk... (the story differs although if you have an SSD).

It explains why rosbag can publish clock information and be setup to replay data slowly so that your disk can keep up with the data that must be displayed (see -r and --clock). The most practicable solution is to simulate your whole graph at a slower rate. If all your nodes uses the ROS time API and are designed to send data at a particular frequency (which is good so you can double check that your nodes run correctly without putting too much pressure on the CPU), it should be totally transparent.

If you really want to achieve real-time, then you have two options:

1. Modify rosbag to first load the whole file in memory and write data back from the memory copy.
2. Use Linux tricks such as mounting a dedicated partition where data is stored directly in the memory (see ramfs or tmpfs) to achieve faster access to the rosbag file.

This is perfectly understandable. You have 300Mb in 2:18s, i.e. ~138Mb/s to achieve real-time. It is likely to be more that your hard-drive maximum bandwidth even if you consider that you are the only process accessing to the disk... (the story differs although if you have an SSD).

It explains why rosbag can publish clock information and be setup to replay data slowly so that your disk can keep up with the data that must be displayed accessed (see -r and --clock). The most practicable solution is to simulate your whole graph at a slower rate. If all your nodes uses the ROS time API and are designed to send data at a particular frequency (which is good so you can double check that your nodes run correctly without putting too much pressure on the CPU), it should be totally transparent.

If you really want to achieve real-time, then you have two options:

1. Modify rosbag to first load the whole file in memory and write data back from the memory copy.
2. Use Linux tricks such as mounting a dedicated partition where data is stored directly in the memory (see ramfs or tmpfs) to achieve faster access to the rosbag file.