Error using ros.BagSel​ection/des​erializeMe​ssages

I am getting the following error trying to read a Rosbag file. Following another questions I have increased the Java heap memory.

I have created a request to Mathworks, but probably the comunity could help also.

I appreciate you help.

Steps to replicate de error.

>> bag = rosbag('/rosbag_file.bag');

>> bag
bag = 
  BagSelection with properties:
           FilePath: '/rosbag_file.bag'
          StartTime: 1.583866799690000e+09
            EndTime: 1.583868599470000e+09
        NumMessages: 1140612
    AvailableTopics: [5×3 table]
    AvailableFrames: {0×1 cell}
        MessageList: [1140612×4 table]

>> bag.AvailableTopics

ans =
  5×3 table
                                          NumMessages           MessageType           MessageDefinition  
    /odo                                    131474       nav_msgs/Odometry            {'  uint32 S [...]
    /Rpm                                    323514       std_msgs/Float64             {0×0 char    [...]
    /flag                                   323514       std_msgs/Bool                {0×0 char    [...]
    /pose                                   323514       nav_msgs/Odometry            {'  uint32 S [...]
    /gps                                     12862       gps_common/GPSFix            {'  uint32 S [...]       

Error when reading a subset:

>>bag2 = select(bag,'Time',[bag.StartTime bag.StartTime + 1],'Topic','/odo');
>>readMessages(bag2);
Error using ros.BagSelection/deserializeMessages (line 641)
Java exception occurred:
java.lang.IndexOutOfBoundsException: Invalid combined index of 1684630641, maximum is 19960408
	at org.jboss.netty.buffer.SlicedChannelBuffer.<init>(SlicedChannelBuffer.java:46)
	at org.jboss.netty.buffer.HeapChannelBuffer.slice(HeapChannelBuffer.java:200)
	at org.jboss.netty.buffer.AbstractChannelBuffer.readSlice(AbstractChannelBuffer.java:323)
	at org.ros.internal.message.field.PrimitiveFieldType$14.deserialize(PrimitiveFieldType.java:599)
	at org.ros.internal.message.field.PrimitiveFieldType$14.deserialize(PrimitiveFieldType.java:565)
	at org.ros.internal.message.field.ValueField.deserialize(ValueField.java:68)
	at org.ros.internal.message.DefaultMessageDeserializer.deserialize(DefaultMessageDeserializer.java:45)
	at org.ros.internal.message.field.MessageFieldType.deserialize(MessageFieldType.java:111)
	at org.ros.internal.message.field.MessageFieldType.deserialize(MessageFieldType.java:38)
	at org.ros.internal.message.field.ValueField.deserialize(ValueField.java:68)
	at org.ros.internal.message.DefaultMessageDeserializer.deserialize(DefaultMessageDeserializer.java:45)

Error in ros.BagSelection/readMessages (line 278)
                msgs = obj.deserializeMessages(obj.MessageList, rows);

Answer 1

[Cam Salzberger]

This looks like the same issue that is mentioned in this bug report. Try reading the messages out of the rosbag using:

msgs = readMessages(bag2, "DataFormat", "struct");

This should allow you to access the data still, though the messages will be structures rather than classes. It has the added benefit of being faster to extract the data from the rosbag. If you have any specialized messages you want to use the convenience methods to extract data from (e.g. readImage, readXYZ, etc.), you can copy the data from the struct message into an empty message object and call the method using that.

We've seen this more commonly with compressed rosbags. If it's an option, and the "DataFormat","struct" isn't enough for you, consider trying to record the rosbag in an uncompressed format.

-Cam

[sbal20]

Thank you very much for your reply, unfortunately extract a structured message did not work also.

>>msgs = readMessages(bagselect1, "DataFormat", "struct");
Caught "std::exception" Exception message is:
ROSLZ4_DATA_ERROR: malformed data to decompress

The specialized messages look really useful, unfortunately I don not have that type of messages in my data. I will analyze the behavior with uncompressed data.

Update:

Uncompressed data was read it smoothly with both commands. Thank you again.