Pretty sure you can. If the game has Redbook CD audio then that's pretty easy. Those are the tracks that use the standard 44,100 Hz 16bit stereo CD audio format. looking at Popful Mail it appears to contain 3 redbook audio tracks mainly the Opening and Ending, and the rest uses PCM which is lower quality audio, i think 8bit mono i forgot. That part is very difficult.
Back in 2017 I was trying to figure out a way to fit TurboGrafx CD and Sega CD games on a Snes classic, this was way before I knew anything about rom hacking. Well in doing so i accidently discovered that I can replace the music tracks with my own audio.
Here's the video tutorial i made: https://youtu.be/pKCX8B2t9p4
Looking back it was very noobish. Basically what i did was degrade the CD audio from 16bit to 8bit, then reconvert it back to 16bit so when I recompress it, it'll take into account the discarded data thus reducing the filesize. It's essentially like compressing your CD albums to mp3, then taking the MP3s and uncompressing it back to wav and burn it onto a CD. Obviously it wont sound as good. And that method would probably be better than what i demonstrated in the video. but i was a noob.
But anyway in doing so i learned that we can swap the audio with our own. This works great for games like
Akumajou Dracula X which contains a lot of redbook audio tracks but not so much for games like Lunar or Popful mail which has sega genesis chip sounds too.
Here's a tool called the PCM to wav:https://www.lunar-net.com/multimedia/utilities.php
It contains a readme for Popful mail that contains a index of where all the dialogue is. On the Popful mail disc you'll see a bunch of bin files, these are the audio samples. This tool can convert it to .wav but I hear that it discards a lot of information making the size smaller. you should get it anyway because it contain some info on popful mail.
I stumbled on this tool called SPCM2WAV which was made for Snatcher:http://junkerhq.net/Snatcher/PCM2WAV/
Now this tool doesn't actually convert anything, it just does some arithmetic to make the sounds playable on PC. Looking at the size of the wav, it's the same size as the .bin file so it's most likely lossless.
Playing the audio back it seems slowed down. I got some experience with modding Playstation audio where when I extract it, the audio pitch is faster. So like for my NBA Jam mod, first I stretch the audio pitch by -4 so sound normal, then i take my custom audio sound and i make it align perfectly with the original PS1 audio, then i reduce the pitch so it's +4. Then when i inject it into the game it playback normally.
Here's how the audo sample sound in the game: https://youtu.be/oyTAUBHYFEI?t=248
I haven't tried modding Sega CD pcms yet but my theory is you're going to have to figure out the correct pitch of the Popful Mail audio (I use sony vegas), then when you insert your own audio, you're going to have to stretch the pitch of it so it matches the sega cd audio. Sounds confusing but it just takes trial and error.
As for converting the wav back to PCM, i haven't found much info on this. However i did find this link:https://forum.jo-engine.org/index.php?topic=947.0;wap2
basically you need ffmpeg and use this command:
ffmpeg -i title.wav -f s16be -ar 8000 -ac 1 TITLE.PCMedit:
that's for sega saturn, i'm reading that Sega CD is supposed to be PCM unsigned 8-bit. so here's the ffmpeg command for that:
ffmpeg -i title.wav -f u8 -ar 8000 -ac 1 TITLE.PCM
It did convert but i havent tried injecting it into the game yet. I might try it tomorrow to see if it works with popful mail. and dont worry about feeling new. we all gotta start somewhere. i was in the same spot a few months ago. i still feel like a complete noob tbh
December 06, 2020, 03:57:19 pm - (Auto Merged - Double Posts are not allowed before 7 days.)
welp i got good news and bad news. The good news is you can swap audio from different regions, the bad news is i couldnt figure out how to encode my own PCM sounds to work properly. But since you're just swapping audio, the Japanese PCM audio clips are all on the disc so you don't have to encode. You just need to take the audio samples from the JP disc, then insert it into the english disc.
Here's a video sample: https://www.youtube.com/watch?v=6Uio48SwEjA
there's more bad news though, the filenames on the Japanese popful mail disc are named differently than the US version. So it may take some time for you to find the correct audio to swap. It would have been much easier if it had the same file names, u could swap it all entirely in probably an hour.
Anyway I'll try to write a guide later. But basically the main program I use is Cdmage.
With cdmage you can open the japanese Popful mail disc image, then extract all the bin data out the disc, then with CDmage you open the US version of popful mail, right click on one of the bin files to swap, I suggest 0050.bin as that's the audio sample i used in the video, then click "Import file", and select one of the Japanese .bin files to test.
If it gives a error saying the file size dont match it's okay because it'll just cut the portions so it'll fit. If you select a longer audio clip then it'll get trimmed.
I recommend getting a hex editor like HxD. This will let you view the and edit the .bin files.