It seems that, after reading the 40 page whitepaper on Pcapng ...
The current PCAP Next Generation (pcapng) Capture File Formatdraft document is 52 pages, so perhaps you're not looking at the most recent version? Other versions do exist, such as those at https://tools.ietf.org/html/draft-tue..., https://pcapng.github.io/pcapng/ or https://www.tcpdump.org/pcap/pcap.html and probably others, but they're all obsolete.
If you're looking for a pcapng parser to help you decipher the file, then look no further than Wireshark itself. If you've loaded a pcapng file into Wireshark, you can use "View -> Reload as File Format/Capture" (Ctrl+Shift+F) to cause Wireshark to load and display the raw file contents itself rather than to load and display the packets from the file. This should cause you to be able to see the various pcapng blocks and be able to drill down into them. For example:
Frame 1: 184 bytes on wire (1472 bits), 184 bytes captured (1472 bits)
MIME file
PCAPNG File Format
Block: Section Header Block 1
Block: Interface Description Block 0
Block: Enhanced Packet Block 1
You can also have a look at the Wireshark source code, such as the epan/dissectors/file-pcapng.c and wiretap/pcapng.c files.
By the way, if you're looking to support all extensions, the Wireshark [PcapNg wiki page] (https://wiki.wireshark.org/Developmen...) has a link to Augmented PCAP Next Generation Dump File Format page that you might also want to take a look at. I don't know how many other extensions may have been implemented but not included in the main pcapng file format specification, but hopefully not many, as this could quickly become problematic with different projects possibly using the same block type for different blocks. That practice should be highly discouraged.
EDIT: Hmm, @guy-harris beat me to the answer ... but how come the askbot didn't warn me that the page was modified? Not sure if I should leave this answer here or delete it. I guess I'll leave it, but only because I included some links to the Wireshark source code, which might also be useful.
