Hotfix for 80286 compatibility

Reconfigure a few instructions, including replacing a conditional near jump with an 80286-compatible equivalent. Also updated the file standard, but none of that takes effect quite yet.

98video.txt

@@ -1,43 +1,60 @@
-Video codec notes
+.98V video codec specification
 Header:
-0x00	"98v"
+0x00	"98V"
 0x03	uint8  framerate (number of GPU frames to skip for every video frame)
 0x04	uint32 number of frames
-0x08	low byte uint8 Sample rate spec
+0x08	low byte uint8
+	86 sample rate spec (bit 0-2)
 	0x00	44100 Hz
 	0x01	33075 Hz
 	0x02	22050 Hz
 	0x03	16537.5 Hz
 	0x04	11025 Hz
-	0x05	8270 Hz
+	0x05	8268.75 Hz
 	0x06	5520 Hz
 	0x07	4130 Hz
-	high byte uint8 Sample depth spec
-	0x00	16-bits
-	0x40	8-bits
-0x0A	uint4[16][3] colour table (rg br gb ...) for all 16 colours
+	Audio type spec (bit 3)
+	0x00	ADPCM (with buzzer compat option)
+	0x08	Buzzer audio
+	Screen resolution spec (bit 4)
+	0x00	640x400 (pixel aspect 1:1)
+	0x10	640x200	(pixel aspect 1:2)
+	Unused (bit 5-7)
+	high byte uint8 Unused
+0x0A	uint4[16][3] colour table (rg br gb ...) for all 16 initial colours
 
 Frame Data:
 Audio Data:
-uint16 length of audio data (16-bit words)
-Then a bunch of 16-bit words containing the audio data for this frame
+0x00	uint16 length of audio data (16-bit words, n)
+0x02	uint16[n] Audio data
+ADPCM:
 The audio data is in 8-bit signed ADPCM format which expands to signed 16-bit PCM
+Buzzer audio:
+The audio data is in 8-bit pulse widths that can be pushed to the buzzer audio control after a shift if necessary
 ADPCM codec:
 	Encodes the difference from the last sample, and applies a bitshift according to the last difference.
 	The first sample is 0x0000, and the initial bitshift is 0. The bitshift value can reach a maximum of 8. 
 	Uses two-complement signed format. The sign is figured out with test data, 0x80, and if it is negative, then abs(data) is not(data) (this is off by one but it doesn't matter).
 	abs(data) <= 0x18: decrement bitshift by 1 after this sample.
 	abs(data) >= 0x68: increment bitshift by 1 after this sample.
+	(My decoder actually uses an acceleration table it creates at startup just to speed things up by using an acceptable amount of memory)
 Video Frame Header:
-0x00	low byte  0000 IRGB  planes to update (automatically determines how many plane sections and which planes they correspond to)
-	high byte 0000 0000
+0x00	low byte  UUUU IRGB  planes to update (automatically determines how many plane sections and which planes they correspond to, U is reserved for 256 colour board compatibility)
+	high byte 0000 000P  update palette?
+0x02	uint4[16][3] colour table (rg br gb ...) for all 16 colours if palette is to be updated this frame, otherwise not included
 Plane Header:
 0x00	uint16 total length of data for this plane
-Plane data chunk:
-0x02	uint16 offset in plane to update (highest bit determines data type: 0 -> copy data, 1 -> fill data
+Fill section:
+0x00	uint16 number of fills (n)
+Plane data chunk (n repetitions):
+0x02	uint16 offset in plane to update
 0x04	uint16 length to update (in 16-bit words)
-0x06	Plane data:
-16-bit words containing data for the plane (copy)
-or
-Single 16-bit word containing the data to fill with (fill)
+0x06	uint16 Single 16-bit word containing the data to fill with
+(repeats as many times as necessary)
+Copy section:
+0x00	uint16 number of copies (n)
+Plane data chunk (n repetitions):
+0x02	uint16 offset in plane to update
+0x04	uint16 length to update (in 16-bit words, m)
+0x06	uint16[m] 16-bit words containing data for the plane
 (repeats as many times as necessary)

src/98videoplayer.asm

@@ -195,7 +195,9 @@ video_read_magicnum_loop: #Check that the file signature is ok
 	test ah, ah
 	jz video_read_end_magicnum
 	xor ah, al
-	jnz video_read_wrongformat
+	jz video_read_stillrightformat
+	jmp video_read_wrongformat #Prevent generating a conditional near jump, which is unsupported below 80386
+video_read_stillrightformat:
 	inc si
 	inc di
 	jmp video_read_magicnum_loop
@@ -484,8 +486,8 @@ PROCEDURE_buzzer_interrupt: #void buzzer_interrupt(void)
 	
 	mov dx, 0x3FDB
 	mov si, cs:currentreadsample
-	push cs
-	pop ds
+	mov ax, cs
+	mov ds, ax
 	lodsw
 	out dx, al
 	xchg al, ah
@@ -577,6 +579,8 @@ PROCEDURE_frameloop: #void frameloop(void)
 	mov di, cs:samplebufferptr
 	push cs
 	pop es
+	mov ax, cs:samplebufferptr
+	mov cs:currentreadsample, ax
 	mov dx, 0xA46C
 	mov cx, cs:adpcmshiftval
 frameloop_buzaudio_pushloop:
@@ -613,13 +617,11 @@ frameloop_buzaudio_pushloop:
 	sar ax, cl
 	xchg ch, cl
 	xor ch, ch
-	add ax, cs:current_sample_midpoint1
+	add ax, cs:current_sample_midpoint2
 	stosw #store sample in buffer
 	mov cl, cs:[bx+accelerationtable_adpcm]
 	dec bp
 	jnz frameloop_buzaudio_pushloop
-	mov ax, cs:samplebufferptr
-	mov cs:currentreadsample, ax
 	jmp frameloop_videodata_process
 	
 frameloop_86audio:
@@ -687,6 +689,39 @@ frameloop_planereadloop:
 	shl ax, 1
 	call PROCEDURE_tryreadsection
 	
+	#Write data fills
+	#mov si, cs:filebuffercurpos
+	#mov ax, cs:[planeseg+bx]
+	#mov es, ax
+	#lodsw #ax has number of fills
+	#test ax, ax
+	#jz frameloop_copystart #If length is zero, skip to doing copies
+	#mov dx, ax
+#frameloop_fillloop:
+	#lodsw #ax has offset
+	#mov di, ax
+	#lodsw #ax has length
+	#mov cx, ax
+	#lodsw #ax has word to copy
+	#rep stosw
+	#dec dx
+	#jnz frameloop_fillloop
+	
+	#Write data copies
+#frameloop_copystart:
+	#lodsw #ax has number of copies
+	#test ax, ax
+	#jz frameloop_planeend #If length is zero, skip to the end of the plane
+	#mov dx, ax
+#frameloop_copyloop:
+	#lodsw #ax has offset
+	#mov di, ax
+	#lodsw #ax has length
+	#mov cx, ax
+	#rep movsw
+	#dec dx
+	#jnz frameloop_copyloop
+	
 	#Write data to planes
 	mov si, cs:filebuffercurpos
 	mov dx, cs:[videolen+bx]
@@ -702,7 +737,7 @@ frameloop_deltaloop:
 	jnz frameloop_filldelta
 	lodsw #ax has length
 	mov cx, ax
-	sub dx, cx
+	sub dx, ax
 	rep movsw #copy time
 	sub dx, 2
 	ja frameloop_deltaloop
@@ -736,8 +771,8 @@ frameloop_planeend:
 								#Hz     44100.0 33075.0 22050.0 16537.5 11025.0  8268.8  5520.0  4130.0
 	sampleratespec_to_buzzfreq:	.word	0x0038, 0x004A, 0x006F, 0x0095, 0x00DF, 0x0129, 0x01BD, 0x0253 #2.4576 MHz bus
 								.word	0x002D, 0x003C, 0x005B, 0x0079, 0x00B5, 0x00F1, 0x016A, 0x01E3 #1.9968 MHz bus
-	shiftdownvalues:			.byte	  0x0A,   0x0A,   0x09,   0x09,   0x08,   0x08,   0x07,   0x07 #2.4576 MHz bus
-								.byte	  0x0B,   0x0A,   0x0A,   0x09,   0x09,   0x08,   0x08,   0x07 #1.9968 MHz bus
+	shiftdownvalues:			.byte	  0x0B,   0x0A,   0x0A,   0x09,   0x09,   0x08,   0x08,   0x07 #2.4576 MHz bus
+								.byte	  0x0B,   0x0B,   0x0A,   0x0A,   0x09,   0x09,   0x08,   0x08 #1.9968 MHz bus
 	old_vsync_vector_offset:	.word	0x0000
 	old_vsync_vector_segment:	.word	0x0000
 	old_timer_vector_offset:	.word	0x0000