https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=5370
--- Comment #12 from Márton Németh <nm127@xxxxxxxxxxx> 2010-11-23 12:16:57 PST ---
Created an attachment (id=5509)
--> (https://bugs.wireshark.org/bugzilla/attachment.cgi?id=5509)
Example Linux USB capture with selected ISO packets
This example capture file contains USB isochronous packets. Each captured URB
(USB Request Block) contains 24 ISO descriptors. The URBs from device to host
direction may contain the data in this case. The packets are from ISO *input*
communication (this might be shown wrongly as "URB_ISOCHRONOUS out" by
Wireshark Version 1.5.0 (SVN Rev 34754 from /trunk), but this is an other
story).
Packet No. 1: URB from host to device, contains the maximum sizes in ISO
descriptors.
Packet No. 2: completed URB (pair of this URB is not shown in this capture
file). ISO descriptors 0..19 contains no data. ISO descriptors 20 and 21
contains data, and fully uses the avaliable 1023 bytes space. ISO descriptors
22 and 23 also contains data but they are using only 202 and 181 bytes
respectively.
Packet No. 3: URB from host to device. The URB is recycled by the application
so it has the same URB id as packet No. 2, but they don't have any other
relationship to each other.
Packet No. 4: completed URB (pair is not shown). All the 23 ISO descriptors
contains some amount of data. Because this is a memory mapped transfer from the
kernel to the userspace each ISO descriptor has the 1023 bytes space but only
the first part of each data block contains valid data.
Packet No. 5: URB from host to device. Again, this is a recycled URB of packet
No. 4.
Packet No. 6: This is the completed URB pair of Packet No. 1. ISO descriptions
0..7 has data. The data length is not fully filling the available 1023 bytes
space. The ISO descriptors 8..24 does not contain data, thus the captured URB
ends at the last useful byte of ISO descriptor 7.
Packet No. 7: URB from host to device.
Packet No. 8: This is the completed URB pair of packet No. 3. None of the ISO
descriptors contain any data, so the captured packet ends right at the end of
the last ISO descriptor.
Packet No. 9: URB from host to device.
Packet No. 10: Pair of packet 9. This is URB is from the end of the ISO input
steam. ISO descriptors 0..13 contains zero data. ISO descriptors 14..23
contains the error code -EXDEV showing that the ISO stream ended.
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