JOTEGO
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YM2151 Accuracy/HDMI Effects
🕑 Added 2021-02-12 20:57:23 +0000 UTC(español abajo)
I started on FPGA retro developments with a Yamaha YM2151 module: the most important chip for arcade games. I made hundreds of measurements, and I designed the FPGA counterpart -JT51- to match those measurements.
But there were two things I couldn't measure: the noise channel and the low-frequency oscillator (LFO). I made an implementation based on Yamaha's public notes. Now, with detailed reverse engineered information available, it was time I went back and reviewed it.
I have spent several days making an exact version of the original LFO and noise channel. The difference is quite noticeable in many melodies and FX sounds. I invite you to start your favourite game and listen to it again.
By the way, thanks to Stefany Allaire, the JT51 is being used now as a replacement for YM2151 chips, as the original parts are becoming scarce.
Cores affected by this improvement: CPS1, Double Dragon 1/2, Bionic Commando, Contra and Street Fighter 1.
The MiSTer firmware recently got support for custom aspect ratios, so you don't have to stick to the default options. I have added support to all cores. Please follow the official Mr's instructions about it.
Finally, I have added an "old TV" option to all cores. It enables a horizontal filter equivalent to a TV with poor bandwidth. It reminds me of my old computer TV. It will look better if you use it together with scanlines (50% at least). The scaler LCD effect also looks very nice with it. This filter is completely optional and can be combined with the old ones.
Please run the updater or grab the files from jtbin.
I had one more thing for this week, but things didn't go as planned. Expect a CPS2 beta update for next week, and possibly other goodies.
Español
Empecé con desarrollos retro FPGA con un módulo Yamaha YM2151: el chip más importante para juegos de recreativa. Hice cientos de mediciones y diseñé la contraparte FPGA -JT51- para que coincidiera con esas mediciones.
Pero había dos cosas que no pude medir: el canal de ruido y el oscilador de baja frecuencia (LFO). Hice entonces una implementación basada en las notas públicas de Yamaha. Ahora, con la información detallada de ingeniería inversa disponible, era hora de pararse y revisarla.
He pasado varios días haciendo una versión exacta del LFO original y del canal de ruido. La diferencia es bastante notable en muchas melodías y sonidos FX. Os invito a poner vuestro juego favorito y volver a escucharlo.
Por cierto, gracias a Stefanie Allaire, el JT51 se está usando como reemplazo de chips YM2151, dada la escasez de estos últimos.
Cores afectados por esta mejora: CPS1, Contra, Bionic Commando, Double Dragon 1/2 y Street Fighter 1.
El firmware de MiSTer recientemente incorporó soporte para relaciones de aspecto personalizadas, por lo que no hay que ceñirse a las opciones predeterminadas. He agregado este soporte a todos los cores. Sigue las instrucciones oficiales de MiSTer al respecto.
Finalmente, agregué una opción de "TV vieja" a todos los núcleos. Permite un filtro horizontal equivalente a un televisor con poco ancho de banda. Me recuerda a mi viejo televisor para el ordenador. Se ve muy bien usado junto con líneas de escaneo (50% al menos). El efecto LCD del escalador también congenia muy bien. NB: este filtro es completamente opcional y se puede combinar con los antiguos.
Tenía algo más para esta semana, pero las cosas no salieron según lo planeado. Espera una actualización de la beta de CPS2 para la próxima semana y posiblemente otras cositas.
Puedes usar el actualizador o directamente descargar desde jtbin.
Comments
JOTEGO
I spent several hours on this last week and I will continue testing the modules to find the bug I introduced. I prefer not to roll back because this version fixed other problems. I will continue working on it this week.
Shane Yates
The instruments sound incorrect now compared to the real hardware for Street Fighter II. The Blanka stage is the most obvious one, the lead tune which is a percussive bell is now weak and out of tune.
David Filskov
Ah well ... as long as he has energy to do it himself it's OK, I think, if he makes it open source. Thanks!
JOTEGO
I have talked with him a couple of times. He seems to enjoy writing his own modules and doesn't seem interested in using other people's work.
David Filskov
Would your work on this be any help to the guy making the NEC PC8801 for MiSTer? - it has a newer FM chip though I think: http://fpga8801.seesaa.net Some tracks from the FM chip that's in 8801: https://www.youtube.com/watch?v=mDosHMMs9vM
