How to replace audio files in Subahibi ?

[sakimotor]

Hi, I've had a pretty silly idea in my mind where I wanted to replace Subarashiki Hibi's soundtrack with custom music. The game contains all it's "bgm" files in the archive "data05000.arc", so I extracted the files from there (with GARbro, making sure that I don't tick the option for converting the audio files) and deleted the archive itself, the game still runs with the music working correctly. 

I then converted an MP3 I had into OGG with Audacity, removed the extension, launched the game and... Playing said music in the Music Room immediately crashed everything. I figured something was wrong with the way my file looked, so I opened it in HxD Editor and compared it to one of the game's default files (I use bgm002 as an example if you're curious).

That is when I realized that the game's music has 0x40 bytes of header data which have 8 bytes of signature ( 40 00 00 00 62 77 20 20), then 4 bytes that give the file size without the header, in little endian notation (so a file of size 0x2213DD will be written as 9D 13 22 00), 4 bytes that will give the sample count of the song, still in little endian notation (so if a file has 6392072 = 0x618908 samples the header will say 08 89 61 00), and finally 3 mysterious lines of header which seemingly always say "44 AC 00 00 02 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00".

 

After that, there is a supposedly normal OGG file, which the game encodes with the 1.0.0 version of libvorbis by the way, indicated by the OGG header that says "Xiph.Org libVorbis I 20020717", an empty tag for the title and artist but one filled tag for the genre (J-POP(J)), then the sound data itself.

 

I have attempted writing the header bytes by hand for my own file: the game didn't crash anymore, but the music was still not playable. I then tried to downgrade my version of libvorbis, and have found an old Audacity release (1.3.0) which still generated OGG files with the 2002 version of the library, at least according to the signature of my resulting files: same result.

 

Is there anything that I am missing ? Thanks in advance !