DPCM samples

References

1. ^ abcThe delta modulation channel (DMC) plays 1-bit delta-encoded samples from $\$C000+64A$, $16L+1$ bytes long, at one of 16 rates; a program can also load its 7-bit output level directly through $4011.WikiNESdev Wiki, “APU DMC”
   How we know

   The NES APU's delta modulation channel (DMC) can output 1-bit delta-encoded samples or can have its 7-bit counter directly loaded, allowing flexible manual sample playback.

   Sample address = %11AAAAAA.AA000000 = $C000 + (A * 64) … Sample length = %LLLL.LLLL0001 = (L * 16) + 1 bytes

   For example, on NTSC (1.789773 MHz), a rate of 428 gives a frequency of 1789773/428 Hz = 4181.71 Hz.

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

2. ^ abcThe game keeps 7 DMC samples in three tables of address, length, and rate bytes, and a request byte picks the entry by its lowest set bit.Codealdonunez/zelda1-disassembly
   How we know

   554    TXA
   555    LDY #$00
   ⋮
   557    INY
   558    LSR
   559    BCC :-
   560    LDA SampleRates-1, Y
   561    STA DmcFreq_4010
   562    LDA SampleAddrs-1, Y
   563    STA DmcAddress_4012
   564    LDA SampleLengths-1, Y
   565    STA DmcLength_4013
   ⋮
   574SampleAddrs:
   ⋮
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

3. ^ abThe samples are sound effects; boss code requests $10 for the Aquamentus, Gleeok, and Ganon roar (entry 4, rate $0E), $20 for the Dodongo and Gohma roar (entry 5), and $02 for a boss hit (entry 1), and DeleteSlot requests $08, which the disassembly labels the "hurt" sound (entry 3).Codealdonunez/zelda1-disassembly
   How we know

   4846    LDA #$10                    ; Play Aquamentus/Gleeok/Ganon roar.
   4847    STA SampleRequest
   

   4900    LDA #$20                    ; Play Dodongo/Gohma roar.
   4901    STA SampleRequest
   

   8493    LDA #$02                    ; Boss hit sound effect
   8494    STA SampleRequest
   

   1770DeleteSlot:
   1771    LDA #$08                    ; "Hurt" sound effect
   1772    STA SampleRequest
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

4. ^The music data has a sample track beside the other channels' tracks; each note byte on it queues a sample, and Music_PlayDMC loads that sample's rate, address, and length from three 16-entry tables and restarts the DMC.CodeSouthbird's SMB3 disassembly
   How we know

   927	LDA Music_PCMTrkPos
   928	BEQ PRG031_E738	 	; If Music_PCMTrkPos = 0 (disabled), jump to PRG031_E738
   ⋮
   936	LDA [Music_Base_L],Y	; Get next byte in music segment track
   

   950	STA DMC_Queue	 	; Store note into DMC queue
   

   94	LDA DMC_MODCTL_LUT-1,Y		; Subtract 1 from LUT address since $00 is disabled and $01 is first DMC sound
   95	STA PAPU_MODCTL	 		; Update PAPU_MODCTL
   ⋮
   98	LDA DMC_MODADDR_LUT-1,Y	; Subtract 1 from LUT address since $00 is disabled and $01 is first DMC sound
   99	STA PAPU_MODADDR	 	; Set PAPU_MODADDR (address of sound)
   ⋮
   107	LDA #$0f	 
   108	STA PAPU_EN	 ; Disable DMC
   109	LDA #$1f	 
   110	STA PAPU_EN	 ; Enable DMC
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger

5. ^ abcThe 16 sample entries play 9 recordings, some reused at a lower rate or cut short; their rate bytes are $0F (33,144 Hz) for most, and $0E (24,858 Hz) or $0D (21,307 Hz) for some of the reused copies.CodeSouthbird's SMB3 disassembly · NESdev Wiki, “APU DMC”revised
   How we know

   163DMC_MODCTL_LUT:
   164	.byte $0F	; Sample  0 (DMC01)
   ⋮
   170	.byte $0E	; Sample  6 (DMC05 3/4 length)
   ⋮
   172	.byte $0E	; Sample  8 (DMC06 slower)
   ⋮
   179	.byte $0D	; Sample 15 (DMC09 even slower)
   

   113	; The address are $C000 | (value << 6)
   114MADR .func ((\1 & $3FFF) >> 6)
   ⋮
   117MLEN .func ((\2 - \1) >> 4)
   

   For example, on NTSC (1.789773 MHz), a rate of 428 gives a frequency of 1789773/428 Hz = 4181.71 Hz.

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Revised after a check by a second AI model, 2026-10-21.

   In the claim ledger

6. ^During the overworld and underwater songs the sound engine raises a counter by 1 a frame up to $30 and writes it to the DMC's output level at $4011; other songs count it back down to 0, and the game plays no samples.CodeXkeeper0/smb1
   How we know

   79	LDY DAC_Counter                              ; load some sort of counter
   80	LDA AreaMusicBuffer
   81	AND #%00000011                               ; check for specific music
   82	BEQ NoIncDAC
   83	INC DAC_Counter                              ; increment and check counter
   84	CPY #$30
   85	BCC StrWave                                  ; if not there yet, just store it
   86NoIncDAC:
   87	TYA
   88	BEQ StrWave                                  ; if we are at zero, do not decrement
   89	DEC DAC_Counter                              ; decrement counter
   90StrWave:
   ⋮
   

   Checked against the evidence by its author, an AI model, 2026-10-21.

   Checked by a second AI model, 2026-10-21.

   In the claim ledger