[DEV] Read/parse the 1.21 replays

coin-au-carre

France6 Posts

January 22 2018 17:06 GMT

As you might know, the replays in sc:r changed compression algorithm from a modified PKWare to a zlib compression until recent patches.

When opening recent replays such as in http://bwreplays.com/ I cannot see any 78 9C magic numbers.

What I have in common when comparing header of two replays is :

a77e 7e2b 0100 0000 0400 0000 7265 5253

or in other terms:

b'\xa7~~+\x01\x00\x00\x00\x04\x00\x00\x00reRS'

Does anyone can help tell what compression it is?

dragonattack

15 Posts

January 22 2018 17:37 GMT

The first one in the list labeled 1.18 contains 78 9c

A7 7E 7E 2B 01 00 00 00 04 00 00 00 72 65 52 53 1E 84 F7 8E 01 00 00 00 B9 00 00 00 78 9C

221 Dewalt 281 SouL)T(Dandy 19 min. FIGHTING SPIRIT 03.12.2017 DOWNLOAD✔ 1.18

coin-au-carre

France6 Posts

January 22 2018 18:46 GMT

Yes that was before 1.21. You don't see this 78 9C in 1.21 replays. But you gave me some precious informations I did not look at the right place.

Edit: Thx I found it with recent replays offset is at 32 if people are interested (it used to be at something like 28 in 1.20 I think).

B-royal

Belgium1330 Posts

January 23 2018 19:51 GMT

Oh really so what is the compression algorithm now?

The data format is something along these lines:

- 4 bytes checksum
- 4 bytes block
- 4 bytes encoded length
- data (compressed or not), if compressed starts with 789c
- in between blocks, 4 bytes for encoded length

I have checked a few 1.21 replays, and they still seem to follow this format but as you say there's no 789c header any more. And I don't know anything about zlib compression past this being a very common one.

00 04h seems to be the start of each compressed data block.

coin-au-carre

France6 Posts

January 25 2018 16:03 GMT

Actually it is still zlib default compression. In the last patch, I can find the 789c header in replays at 32 offset.
It's dirty but I put a dynamic offset (assuming the compression algorithm is not modified) so that I do not care about changing manually this offset in future patches.

I have made a Discord bot that read basic infos from a replay you post in the chat. If you guys are interested it is available in the BW FRA-1 discord. [image loading]

B-royal

Belgium1330 Posts

January 25 2018 17:03 GMT

Nice. In that case, could you try it/have a look at this replay? I don't think this one has a 789c header anywhere. And I downloaded this one a few days ago from bwreplays.com so I assume it's the latest patch (I could be wrong).

https://www.dropbox.com/s/i4qpf5xvs0op4tw/lg2nz_ebla_Heize_1.rep?dl=0

coin-au-carre

France6 Posts

January 25 2018 17:47 GMT

Yep I can't find the header either ~~. It might be older patch. And I guess it can be an old replay even if it's uploaded on bwreplays.

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