Hacking IMPOSSIBLE MISSION with voice samples

[DracIsBack]

I've been playing the 7800 IMPOSSIBLE MISSION, which (now that I have the 'fixed' version) is a solid translation. One thing that is sadly missing are the classic C64 voice samples of the mad scientist taunting.

 

While the 7800's TIA isn't particularly strong, it is capable of doing voice synthesis and digitized music (see JINKS) and I was wondering how difficult it would be to hack an IMPOSSIBLE MISSION with the voice synthesis included?

[EricBall]

Note that Jink's digitized speech & music occurs only during the static title etc screens. This is because the game needs to update the TIA every line (15.7KHz sampling) for best quality, which make it basically impossible to do any useful CPU work.

 

Digitized speech & sound are also pigs for ROM space. For pure PCM the TIA has a 4 bit volume register, so you're looking at almost 8Kbytes per second. It may be possible to compress that somewhat, though that will obviously increase code complexity and increase RAM usage.

[Wrathchild]

From what I've seen in the original C64 code, the data is already 4 bit volume only that decompresses as it goes into a smaller working buffer. I think the data itself was only around the 16KB size and the playback code between 1&2K.

[DracIsBack]

Note that Jink's digitized speech & music occurs only during the static title etc screens.  This is because the game needs to update the TIA every line (15.7KHz sampling) for best quality, which make it basically impossible to do any useful CPU work.

 

Digitized speech & sound are also pigs for ROM space.  For pure PCM the TIA has a 4 bit volume register, so you're looking at almost 8Kbytes per second.  It may be possible to compress that somewhat, though that will obviously increase code complexity and increase RAM usage.

946954[/snapback]

 

 

In the C64 version, I think the game freezes as well when the voice is speaking.