It is currently Thu Nov 15, 2018 5:11 am

All times are UTC - 7 hours





Post new topic Reply to topic  [ 9 posts ] 
Author Message
PostPosted: Fri Aug 31, 2018 6:43 pm 
Offline
User avatar

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 6950
Location: Canada
A few weeks ago NewRisingSun made an heroic effort to measure at least one copy of every N163 game. I measured what I had at the time too.

I want to keep going with this, so the last few days I wrote a set of simple and easy volume test ROMs for all the current expansions. If you don't have a Famicom or any expansion carts, just measure your APU. That still helps.

You can find the ROMs in the build folder here: https://github.com/bbbradsmith/nes-audio-tests

I can add more tests if I get my hands on other expansion audio carts, or if you've got some you can write tests for you can submit them to me. The source is there, the individual code for each test is pretty small.

The measuring process is like this:

1. Load the ROM in your dev-cart, hear the buzz when it starts.
2. Quickly pull it out*, and insert the cart to be measured. (You have a little more than 4 seconds.)
3. If you hear a second buzz, you succeeded. Otherwise start over.
4. The test will play and then loop, each time starting this a quick buzz.
5. Record the test and compare the RMS of the two tones. (Audacity's Analyze > Contrast tool will do this.)
6. Post here with your results.

* In my personal experience hotswapping cartridges has been a safe procedure, but some people are uncertain about this. I cannot make any guarantee, so if you are not comfortable with the risk, please do not do these tests. (The APU test does not require a hotswap, though. Neither does FDS if you can use the .FDS image.)

Each ROM plays an APU square wave at 440Hz, followed by an "equivalent" sound on the expansion. The sounds are played on a single channel at their maximum volume. The APU test doesn't require a hotswap (or a Famicom), it compares against the triangle. The VRC7 can't produce a square wave, so I used an instrument that has a 2:1 modulator at 50% modulation strength that makes a dull square-ish sound. (Maybe not the ideal comparison, but should be simple and reliable to execute.) The 5B has a strange amplifier, so its test uses volume 12 instead of 15, where it appears to be linear. The N163 always uses 1-channel mode.


Here's my test results. I have an AV modded Famicom (all the expansions are tested on this), and a Canadian NES. All the expansion audio tests were done with the Famicom. The APU tests were done with each of the machines:

  • Gimmick! - db_5b: -1.3dB
  • Erika to Satoru no Yumebouken: db_n163: 19.2dB
  • Rolling Thunder - db_n163: 17.2dB
  • Uchuu Keibi Tai SDF - db_mmc5: 1.0dB
  • Just Breed - db_mmc5: 1.0dB
  • Esper Dream 2 - db_vrc6b: 0.2dB
  • Lagrange Point - db_vrc7: 11.3dB
  • FDS - db_fds: 6.6
  • Famicom - db_apu: -0.3dB
  • NES - db_apu: 0.1dB

Keep in mind that every time I do measurements like this the results are slightly different. Temperature variation etc. affects this, so we don't need to be super precise here. This is a shotgun survey approach. Accurate to within .1dB is probably already too fine. The last time I measured my N163 carts they both came out 0.3dB louder, for example.

This is partly motivated by wanting to get mixing data for N163 into the NSF format, but it would be great to have better survey data on this stuff just so we can get a better average for emulation.

Edit: the 5B test was revised after investigating its amplifier. VRC7 test was revised after feedback was suggested.


Last edited by rainwarrior on Mon Sep 03, 2018 1:19 am, edited 4 times in total.

Top
 Profile  
 
PostPosted: Fri Aug 31, 2018 7:41 pm 
Offline
User avatar

Joined: Sun Sep 19, 2004 9:28 pm
Posts: 3677
Location: Mountain View, CA
Several questions:

* How are these tests reliable, given that there is going to be mass variance between everyone's recording/audio capture setups? Does it not matter because the comparisons are being done against samples both recorded by the same person/same machine/same test session?

* These ROMs require devcarts that have actual hardware mappers on them, e.g. a modified Famicom cart that contains a real VRC6 chip on it, correct? Next question is related:

* Powerpak and Everdrive cannot be used for these tests (because said devices provide emulation of said audio, and because likely pulling out these carts while the system is on would probably not work like a real cartridge would and possibly be extremely bad for the CPLD or underlying CF/SD), correct?

* Would you like separate APU levels for different versions of consoles? For example, Famicom vs. Famicom AV, NES front-loader vs. NES top-loader, Sharp Twin Famicom (this one has gotten a lot of scrutiny over the years) (and there are multiple revisions of this thing too; this guy seems to have at least 4 revisions), etc.?

* Would you like APU levels for the RetroUSB AVS? I'm thinking no/not relevant because it's not a "real" NES, but thought I'd ask anyway.


Top
 Profile  
 
PostPosted: Fri Aug 31, 2018 7:58 pm 
Offline
User avatar

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 6950
Location: Canada
koitsu wrote:
* How are these tests reliable, given that there is going to be mass variance between everyone's recording/audio capture setups? Does it not matter because the comparisons are being done against samples both recorded by the same person/same machine/same test session?

The tests are against the APU inside the machine. Yes it will vary from machine to machine. That's the point. I'm trying to get a survey to understand the average and range.

koitsu wrote:
* These ROMs require devcarts that have actual hardware mappers on them, e.g. a modified Famicom cart that contains a real VRC6 chip on it, correct?

No. You start the ROM with a devcart, then hotswap to a famicom cartridge that has the expansion. (Or in the case of the APU test you just run it.) Every tests has both an NROM version (so it should run on any devcart) and a version with the specific mapper (so you can test an emulator, or run it on a cart that has that mapper, etc.) You don't need any modified carts.

koitsu wrote:
* Powerpak and Everdrive cannot be used for these tests (because said devices provide emulation of said audio, and because likely pulling out these carts while the system is on would probably not work like a real cartridge would and possibly be extremely bad for the CPLD or underlying CF/SD), correct?

I've done hotswaps hundreds of times at this point, and I have never heard a report of a cartridge damaged by hotswapping. I'm pretty confident the risk is low, but if you think it's a problem don't do the test. I can't say for certain it's 100% safe. (Definitely don't do it if you've got an important save game stored on the cart, though.)

koitsu wrote:
* Would you like separate APU levels for different versions of consoles? For example, Famicom vs. Famicom AV, NES front-loader vs. NES top-loader, Sharp Twin Famicom (this one has gotten a lot of scrutiny over the years) (and there are multiple revisions of this thing too; this guy seems to have at least 4 revisions), etc.?

I'll take whatever I can get. Just describe the hardware that's being used for each test.

koitsu wrote:
* Would you like APU levels for the RetroUSB AVS? I'm thinking no/not relevant because it's not a "real" NES, but thought I'd ask anyway.

It's fine to include. Just accurately describe what's being used. It's just more data; whoever looks at it can decide whether it's relevant to what they're trying to understand.


Top
 Profile  
 
PostPosted: Fri Aug 31, 2018 8:20 pm 
Offline
User avatar

Joined: Sun Sep 19, 2004 9:28 pm
Posts: 3677
Location: Mountain View, CA
Thanks for the answers! Much more clear to me now. Makes me wish I hadn't sold my Famicom carts earlier this year (I had several with expansion chips, particularly a couple with N163). Should be able to provide general APU level results though.

Awesome and super useful project, BTW.


Top
 Profile  
 
PostPosted: Sun Sep 02, 2018 11:55 pm 
Offline
User avatar

Joined: Fri Nov 12, 2004 2:49 pm
Posts: 7570
Location: Chexbres, VD, Switzerland
I'd gladly help with my FDS and Just Breed cart, but alas I do not have a working Flashcart anymore.

Quote:
The VRC7 can't produce a square wave, so I used an instrument that has a 2:1 modulator at 50% modulation strength that makes a dull square-ish sound.

I'm fairly sure if you enable "feedback", you can get an almost perfect square wave.


Top
 Profile  
 
PostPosted: Mon Sep 03, 2018 12:15 am 
Offline
User avatar

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 6950
Location: Canada
Bregalad wrote:
Quote:
The VRC7 can't produce a square wave, so I used an instrument that has a 2:1 modulator at 50% modulation strength that makes a dull square-ish sound.

I'm fairly sure if you enable "feedback", you can get an almost perfect square wave.

Ah! That's good. Yeah I had tried feedback and some other combinations, but just adding full feedback to the instrument I described above does make a better approximation of a square wave. (I hadn't tried it with that particular combo.) It's not a "perfect" square wave, it is still dull, but it is less dull and brings the spectrum slightly closer. I should probably revise the test to do this instead.

The main goal is just to have a test that is a reliable standard. If the square wave spectrums can match, that's ideal, since that would be more robust against additional/external filters, but for VRC7 (and APU) I had to find some sort of compromise.


Top
 Profile  
 
PostPosted: Tue Sep 11, 2018 5:12 am 
Offline
User avatar

Joined: Fri Nov 03, 2017 11:54 pm
Posts: 12
I have a HVC-CPU-07 and two AV Famicoms.
I also have Akumajou Denstsu (VRC6), Erika to Satoru (Namco 163), Megami Tensei II (Namco 163), Lagrange Point (VRC7), and Just Breed (MMC5).
I'll start with a AV modded HVC-CPU-07 through pin 46 (shielded cables and all) since all the expansion audio carts were made for it.

Measurement results:
Delta of RMS values without the initial peak on note start.

Code:
Famicom HVC-CPU-07 - db_apu: -0.03dB
Akumajou Densetsu - db_vrc6: -1.11db (expansion slightly quieter as it should).
Lagrange Point - db_vrc7: 10.88dB
Just Breed - db_mmc5: 0.05dB
Megami Tensei II - db_n163: 11.58dB
Erika to Satoru - db_n163: 18.16dB


Image
Image


Top
 Profile  
 
PostPosted: Tue Sep 11, 2018 6:30 am 
Offline
User avatar

Joined: Fri Nov 03, 2017 11:54 pm
Posts: 12
I see our results are within 0.5-1db from one another, that's very accurate in analog standards.
I can also say from what I hear and the measurement readings that all expansion audio carts were designed for pre GPM (non-FF VCCI) Famicom console, that includes the newer Just Breed and Gimmick! too.

I hope our efforts will translate to a better emulators default audio balance levels, they are close but not accurate as they can be.
It also helps with the Everdrive N8 that now has volume control for the expansion audio.


Top
 Profile  
 
PostPosted: Tue Sep 11, 2018 2:14 pm 
Offline
User avatar

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 6950
Location: Canada
I should import from the other thread some equivalent N163 measurements that were made there:

Set by NewRisingSun:
NewRisingSun wrote:
Code:
Game                            dB difference
Namco Classic II                2.0 *
Final Lap                       12.7
Sangokushi II: Haō no Tairiku   12.9
Megami Tensei II                13.0
Rolling Thunder                 16.9
King of Kings                   18.0
Mappy Kids                      18.6
Erika to Satoru no Yume Bōken   18.8
Yōkai Dōchū-ki                  18.9
Sangokushi: Chūgen no Hasha     19.5
* Namco Classic II presumed to be an invalid result due to possible modification of its board.

Set by jrlepage:
Quote:
Code:
Rolling Thunder                 16.0
Final Lap                       11.2
King of Kings                   17.3
Megami Tensei 2                 11.9


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 9 posts ] 

All times are UTC - 7 hours


Who is online

Users browsing this forum: Google [Bot] and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group