Search found 429 matches

by James
Thu Sep 29, 2016 12:35 pm
Forum: NESemdev
Topic: Understanding sound for the first time
Replies: 12
Views: 4166

Re: Understanding sound for the first time

Don't worry about DSP for now. Once you get it working, you may choose to learn some DSP stuff to implement better resampling, etc., but there's no DSP involved in generating the APU output (well, unless you count downsampling the signal to e.g., 48kHz, but that's as simple as taking every ~37th sam...
by James
Fri Aug 19, 2016 7:39 am
Forum: NESdev
Topic: Nesdev.com funding
Replies: 78
Views: 197955

Re: Nesdev.com funding

I have been paying the co-location and other fees for the past couple of years and can continue to do so, I have not been able to set any extra aside to put towards a new server. ... im not concerned as far as the current costs as I can and will be able to cover them. It is more about trying to get...
by James
Thu Jul 21, 2016 6:37 am
Forum: NESemdev
Topic: What are some "easy to emulate" games ?
Replies: 11
Views: 3994

Re: What are some "easy to emulate" games ?

I used the Zelda Title Screen Simulator during the initial development of my emulator. The first game I got to run was Arkanoid.
by James
Fri Jul 01, 2016 2:18 pm
Forum: NESemdev
Topic: Important screensaver tip for Windows emulator authors
Replies: 31
Views: 90026

Re: Important screensaver tip for Windows emulator authors

cool -- just tested the Power Management API and it seems to work well. Even with my workstation set to lock. Thanks!
by James
Tue Jun 28, 2016 9:02 am
Forum: NESemdev
Topic: MMC5 Castlevania III - garbled castle first floor
Replies: 15
Views: 4732

Re: MMC5 Castlevania III - garbled castle first floor

Are you properly handling this scenario?

- CPU I flag set
...
- MMC5 asserts IRQ (CPU should ignore)
...
- CPU I flag cleared (e.g., CLI or PLP) <-- IRQ should be handled here (after the next instruction)
by James
Tue Jun 28, 2016 5:32 am
Forum: NESemdev
Topic: MMC5 Castlevania III - garbled castle first floor
Replies: 15
Views: 4732

Re: MMC5 Castlevania III - garbled castle first floor

I had the same problem and it turned out to be a CPU issue. I don't recall the exact details, but I think it had to do with handling the case where the interrupt disable flag was cleared while the irq line was being asserted.
by James
Mon Jan 18, 2016 2:56 am
Forum: NESemdev
Topic: Audio rendering?
Replies: 33
Views: 7419

Re: Audio rendering?

oRBIT2002 wrote:To me it seems difficult to calculate those waves in realtime (more or less), applying sweeps and such..
Read through Blargg's APU reference if you haven't already (http://nesdev.com/apu_ref.txt). The block diagrams are really helpful.
by James
Mon Jan 11, 2016 12:54 pm
Forum: NESemdev
Topic: PPU timing?
Replies: 42
Views: 14628

Re: PPU timing?

Which games are you having problems with?
by James
Tue Dec 01, 2015 11:46 am
Forum: NESemdev
Topic: A couple of questions about MMC3
Replies: 14
Views: 4228

Re: A couple of questions about MMC3

It should be noted that the MMC3 board is linked to the /IRQ pin through additional logic. Essentially, an OR-gate is required to allow other components, such as the APU, to also have an opportunity to attempt to interrupt the processor. There is a pull-up resistor attached to /IRQ that normally ke...
by James
Sun Aug 02, 2015 7:10 pm
Forum: NESemdev
Topic: Invisible platforms in super mario
Replies: 8
Views: 2577

Re: Invisible platforms in super mario

I'm unsure about the "platform", but there's something wrong with your sprite 0 hit detection code.
by James
Mon Jul 06, 2015 2:41 pm
Forum: NESemdev
Topic: Some advice of DSP here...
Replies: 97
Views: 16629

Re: Some advice of DSP here...

zeroone wrote:
James wrote:Here's some code for designing a filter and converting it to second order sections. Use the coefficients (Bs and As) to implement each section as a transposed direct form II filter.
Why form II instead of form I ?
http://www.earlevel.com/main/2003/02/28/biquads/
by James
Sat Jul 04, 2015 12:56 pm
Forum: NESemdev
Topic: Some advice of DSP here...
Replies: 97
Views: 16629

Re: Some advice of DSP here...

all the mathematical packages that do this automatically use iterative approaches to working out the filter constants. Unfortunately, I don't have access to them Sure you do. Check out GNU Octave . Here's some code for designing a filter and converting it to second order sections. Use the coefficie...
by James
Fri Jul 03, 2015 7:12 pm
Forum: NESemdev
Topic: Some advice of DSP here...
Replies: 97
Views: 16629

Re: Some advice of DSP here...

This is what I'm doing. A series of biquad filters. And, this is what happens if you cascade 100 8th-order Butterworth filters with a cutoff frequency of 24000 Hz (red is the filter, blue is the cascade). Some gain is lost, a ringing appeared on the left and the drop-off slope did not increase all ...
by James
Fri Jul 03, 2015 7:00 pm
Forum: NESemdev
Topic: Some advice of DSP here...
Replies: 97
Views: 16629

Re: Some advice of DSP here...

Here's an example. Noise mode 1, period 5. Not decimated 2x decimated It doesn't have a period 5. The shortest periods are 4, 8, 16, and 32. All periods in the LUT are even, in fact. Can you hear a difference between CPU and CPU/2 for any even period? Good catch; my little test generator script was...
by James
Fri Jul 03, 2015 3:50 pm
Forum: NESemdev
Topic: Some advice of DSP here...
Replies: 97
Views: 16629

Re: Some advice of DSP here...

I assume the aliasing is audible with tonal noise... is it audible when the LFSR's in full white noise mode? mode = 0? No. mode = 1, yes. Here's an example. Noise mode 1, period 5. Not decimated 2x decimated I think that is why James only used a 4th order Butterworth filter and combined it with an ...