[Module IO] savePCDFile() function does not save the PCLheader information of the point cloud

[Pedrous]

savePCDFile() function does not save the PCLHeader information that contains sequence number, timestamp and frame id information. Therefore, this is information is lost when saving and loading the data.

We use the timestamps of each cloud and point recorded in a moving platform and now we need to save this information into separate text file.

I would expect that this information could also be saved and not just used internally in PCD but now it is completely lost.

Environment:

• OS: Ubuntu 20.04
• Compiler: GCC 9.4.0
• PCL Version: 1.10

[mvieth]

Hi, I see how it could be useful to store this information in the PCD file, but the problem is that the current PCD file format specification ( https://pcl.readthedocs.io/projects/tutorials/en/master/pcd_file_format.html ) does not allow such new header fields. If we make savePCDFile write any new header fields, third-party PCD readers will either refuse to read those files completely, crash, or will ignore the new header fields. Technically we would have to update the PCD file format version (0.7 to 0.8), which would be a big step and again it would be unclear how third-party readers would react to that. One option that might be possible is to store that information (sequence number, timestamp, etc) in a comment (e.g. # TIMESTAMP 123456789). That would mean that any reader is free to use or ignore this information, and no guarantee is given. On the other hand, it might have unforeseen consequences if a PCD reader starts parsing the comments. Not sure if any other file formats have a similar situation?