R13 Issues, R14 Plans

Over the past week I've started making plans for what I want to do for R14.

To start with, R13 introduced a couple of issues which I want to fix. Firstly, a number of roms now no longer work with dynarec enabled, or show odd behaviour. For instance, Aerogauge now finishes the race as soon as the countdown completes. I've tracked this down to one of the dynarec optimisations I added in August, where I optimise fragments which jump back to themselves. This should be a 'safe' transformation, so it suggests there's a bug somewhere in my implementation. If I can't fix the bug in time for R14, I'll add a temporary setting to allow this optimisation to be disabled on a rom-by-rom basis (much like the 'dynarec stack optimisation' setting).

Secondly, it looks like something I changed for savestate support has broken the 'return to main menu' option. I added some logic to help ensure that when taking a snapshot for the savestate, the CPU is paused in a 'safe' state (i.e. no dynarec code is executing, nothing is running on the RSP, and nothing is executing in the branch delay slot.) It looks like I've messed something up which is causing the 'return to main menu' option to wait for a safe state before bailing out to the menu. Should be an easy one to fix.

Morgan suggested a nice idea in the comments, which is that I generate a thumbnail for the savestate as it is created to display alongside the slot in the UI. It's a little tricky to implement, as by the time the emulator is told to create a savestate, it has already obliterated the n64's framebuffer with the Daedalus UI. I'll have to do something quite clever like speculatively copy the n64's framebuffer into system memory every time you enter the Pause Menu, or create the screenshot on the first frame rendered after saving. Either way, I'd like to add this simple feature to R14.

Next on my list for R14 is to look at making more significant performance improvements. Over the months many people have been asking when I'd get around to implementing audio on the PSP's Media Engine. I've talked about this before, but always kept putting it off in order to work on easier optimisations.

The Media Engine is a bit of unknown territory for me. Even though it's practically identical to the main CPU, you can't just change a setting an suddenly have your code running on it. There are a number of small hurdles I have to overcome before I can get audio working on the ME, but this is my big goal for R14 (I'll save the technical discussion for the next post.) If all goes to plan this should mean that audio can always be enabled without a significant impact on framerate.

So in summary for R14: a few bug fixes, thumbnails for savestates, and audio without affecting framerate.

-StrmnNrmn

Back Online

Apologies for the lack of updates. I've not had internet access at home since moving flat at the end of August. My ADSL was activated today so I'm finally up and running again. I can't believe how long it's taken!

Between the flat move and a busy few weeks at work (getting ready for the Tokyo Game Show) I've not had that much time to work on Daedalus, but I have made some progress on a really cool feature people have been asking for for some time, namely savestate support.

For those not familiar with savestates, the basic premise is very much like 'hibernate' or sleep modes on PCs and laptops. A savestate can be created at any point during emulation. At a later time the savestate can be reloaded to restore the emulator to the exact state it was in when the savestate was created.

What's really useful about savestates is that they work even if the underlying save mechanism used by a rom isn't supported properly. I'm hoping that by adding savestate support Daedalus will become significantly more usable for many roms. Savestates also make development a lot easier as it means I can jump straight into the middle of a game when debugging/profiling rather than sitting through the title sequence dozens of times.

I still have a little bit of work left to do on the savestate system, mostly on the UI side, but there are a number of additional optimisations I want to finish off before I release R13. I'm currently planning to get everything ready for release on either the weekend of the 29th Sept, or possibly the first weekend in October.

-StrmnNrmn