18 KiB
Digital Video Cartridge
Decodes MPEG1 audio and video. * 352 x 288 pixel resolution * ISO 11172-1 MPEG1-Stream * ISO 11172-2 MPEG1-Video * ISO 11172-3 MPEG1-Audio
There are multiple models available
- 22ER9141 (with analog video provided to base machine)
- 22ER9956 (with digital video to the base machine)
There are different chipsets available
- GMPEG
- Based on a custom chipset
- VMPEG
- Based on the MCD251 which decodes only the video
- Audio and Video decoded by different subsystems
- Motorola DSP56001FC33 seems to be doing Audio in software
- IMPEG
- Based on the MCD270 with audio and video decoding integrated into one
- Uses 512kB of RAM for buffering and reconstruction
Time and Durations
Periods in certain time systems. Since this can be totally confusing, here some notes.
33 bit 32 bit 16 bit
90 khz 45 kHz 703.125 Hz 30 MHz
25 Hz 3600 1800 28.125 1200000
30 Hz 3000 1500 23.43 1000000
50 Hz 1800 900 14.0625 600000
60 Hz 1500 750 11.71875 500000
Some registers and variables
FMA DCLK 45 kHz 00E03010 long word
GEN_PICT_RATE 90 kHz 00E040A8 word
GEN_DEC_TIM1 703.125 Hz 00E040A0 word
GEN_SYSCR 703.125 Hz 00E04098 word
V_SCR 22.5 kHz long word in FMV driver
Some possible operations to not forget. Often found in the driver code
22.5 kHz >> 5 = 703.125 Hz
45 kHz >> 6 = 703.125 Hz
90 kHz >> 7 = 703.125 Hz
22.5 kHz / 32 = 703.125 Hz
90 kHz / 128 = 703.125 Hz
Offsets between Video and Audio are declared in 22.5 kHz
Example: When starting mv_cdplay() in sync wait mode first and
ma_cdplay() with an offset of 11250, it will result into
playback of audio half of a second earlier than video.
If the offset is -11250, it should result into playback of video half of a second earlier than audio.
But no, it just stops, for some reason.
If ma_cdplay() is started in wait mode and make mv_cdplay() the follower an offset of 11250 in the latter, will result into playback of audio half of a second earlier than video too.
An offset in the first waiting one is ignored.
FMV Timer
V_SCR is used in the driver for representation of the System Clock Reference. According to the driver sources
TenmS equ 56 value for something about 10 mS interrupt
TenSCR equ 896 SCR count during 10 mS
Why 896? Usually 90000/100 would be 900!
The timer resolution is 90 kHz / 16 (or 45 kHz / 8)
90000/56/16 = 100.446428571429
As the driver coder has indicated, 10 mS are not possible. The SCR increment is adapted to that.
90000/56.25/16 = 100.446428571429
90000/896 = 100.446428571429
Mystery solved, though, it might be possible that this is irrelevant. Since V_ExtSCR is set in the FMV driver, the dclk of FMA is utilized. This is the connection where the audio clock (that is synchronized to the disc rotation), is connected with the SCR of the video footage.
Syscalls
MVStat
Result structure according to https://github.com/TwBurn/cdi-docs/blob/main/mv_cbnd.md
typedef struct _motionstatus {
unsigned short MVS_LCntr; /* loops remaining */
char *MVS_CurAdr; /* address to retrieve data */
unsigned int MVS_Speed; /* display speed */
unsigned int MVS_ImgSz; /* image size of current stream */
unsigned int MVS_TimeCd; /* timecode of current picture */
unsigned short MVS_TmpRef; /* temporal reference */
unsigned short MVS_Stream; /* current stream number */
unsigned char MVS_PicRt, /* picture rate */
MVS_Res1; /* reserved */
unsigned int MVS_DSC, /* Video decoder system clock */
MVS_Res2; /* reserved */
} MotionStatus;
Source of this info according to getstat.a
MVS_LCntr <- V_LCntr
MVS_CurAdr <- V_CurAddr + V_Offset
MVS_Speed <- V_ChipSpd
MVS_ImgSz <- V_PWI
MVS_TimeCd <- SYS_TCL (long read at 0x0E04058)
MVS_TmpRef <- SYS_VSR (short read at 0x0E0405C)
MVS_Stream <- V_Stream
MVS_PicRt <- V_PRPA
MVS_DSC <- V_SCR
Timing of events
Detection of a stream end
The FMV driver adds 00 00 01 B7 at the end of the stream in case it ends unexpectedly.
It does that at least in hostplay mode. CD? Not yet confirmed.
The code can look something like this
00 00 01 BA 21 00 01 00 01 C3 33 67 Pack header 00 00 01 E0 00 06 0F PES Header 00 00 01 B7 00 Sequence End
This should be used to detect the stream end.
FMV
The green book is not very clear about the timing of the OS events. This is a measurement (using soundcard) of the UART on the top channel and video on the bottom. When the application is getting a PIC event, a character is printed.
It clearly shows that the PIC event is more related to the start of a picture and not the finished display of one.
FMA
MA_TRIG_DEC is occurring without much delay before samples are provided to the DAC. If there is a decoding delay, it is about 4ms and therefore can be ignored.
This means that the timing of MA_TRIG_DEC can be compared in software to check for synchronization.
Green Book
According to 4.3.2.2 the maximum picture size depends on the frame rate
- With 30 Hz it is 352 * 240
- With 25 Hz it is 352 * 288
If played from disc, the maximum bitrate is 1.4 Mbit/sec.
I, P and B frames are supported.
The data is stored in packs of 2324 bytes.
The minimum size of the MPEG Video Buffer is 512 kB.
MPEG1
Encoding via ffmpeg and muxing via mplex
ffmpeg defines some presets for encoding VideoCD MPEG1 streams. According to the documentation these are the resulting parameters
pal:
-f vcd -muxrate 1411200 -muxpreload 0.44 -packetsize 2324
-s 352x288 -r 25
-codec:v mpeg1video -g 15 -b:v 1150k -maxrate:v 1150k -minrate:v 1150k -bufsize:v 327680
-ar 44100 -ac 2
-codec:a mp2 -b:a 224k
ntsc:
-f vcd -muxrate 1411200 -muxpreload 0.44 -packetsize 2324
-s 352x240 -r 30000/1001
-codec:v mpeg1video -g 18 -b:v 1150k -maxrate:v 1150k -minrate:v 1150k -bufsize:v 327680
-ar 44100 -ac 2
-codec:a mp2 -b:a 224k
For some reason, the CD-i bridge application will not play the resulting MPEG stream. The free version of TMPGEnc can be used to remux the stream to fix this problem. Another method is mplex, which is also available for Linux. On Debian you will find it in the mjpegtools package
It is possible to encode video and audio separate and mux it together. For a simple example, we are encoding with ffmpeg, then demux with ffmpeg, only to mux it back together with mplex.
ffmpeg -y -i "$1" -threads 1 -target ntsc-vcd output.mpg
ffmpeg -y -i output.mpg -vcodec copy -an output_video.m1v
ffmpeg -y -i output.mpg -acodec copy -vn output_audio.mp2
mplex -f 1 output_audio.mp2 output_video.m1v -o output.mpg
The resulting stream can be authored into a VideoCD with tools like vcdxbuild
Authoring of Video CDs
Since a configuration file is required, use tools like k3b to create it. Usually a VideoCD can be created just with this application. Under the hood, vcdxbuild is used.
For fine tuning, the configuration can be exported and the tools can be called from shell.
vcdxbuild --cue-file=VIDEOCD.cue --bin-file=VIDEOCD.bin config.xml
Keep in mind that the CD-i bridge application must be activated in configuration!
At least on Debian, the binary files inside the k3b-data package were broken and were sourced from somewhere else for replacement.
Memory Map of IMPEG
1MB of additional system memory at 0xd00000
412kB of MPEG memo
The DVC MPEG related registers are mapped at 0xe00000 into the CPU memory map
0x040da Is written 0x0201 before doing anything (Reset?)
Is written 0x005c when Microcode was transfered (Go?)
0x04800 Video Microcode? Write ends at 0x004cd4
0x05000 Video Microcode? Write ends at 0x0054d4
0x05800 Video Microcode? Write ends at 0x005cd4
0x06000 Audio Microcode?
0x06800 Audio Microcode?
0x07000 Audio Microcode?
0x40000 ROM driver code for OS9 (256kB)
0x80000 RAM for MPEG decoding (512kB)
Registers of VMPEG
Temporal buffer registers
0x0000 T_STAT
0x0002 T_PWI
0x0004 T_PHE
0x0006 T_PRPA
0x0008 T_TCL
0x000a T_TCH
0x000c T_VSR
0x000e T_BX
0x0010 T_BY
0x0012 T_DCMD
Display control buffer 0
0x0014 B0_STAT
0x0016 B0_PWI
0x0018 B0_PHE
0x0020 B0_PRPA
0x0022 B0_TCL
0x0024 B0_TCH
0x0026 B0_VSR
0x0028 B0_BX
0x002a B0_BY
0x002c B0_DCMD
Display control buffer 1
0x002e B0_STAT
0x0030 B0_PWI
0x0032 B0_PHE
0x0034 B0_PRPA
0x0036 B0_TCL
0x0038 B0_TCH
0x003a B0_VSR
0x003c B0_BX
0x003e B0_BY
0x0040 B0_DCMD
Display control buffer 2
0x0042 B0_STAT
0x0044 B0_PWI
0x0046 B0_PHE
0x0048 B0_PRPA
0x005a B0_TCL
0x005c B0_TCH
0x005e B0_VSR
0x0060 B0_BX
0x0062 B0_BY
0x0064 B0_DCMD
Attenuation of FMA
Example syscall recorded in cdiemu
@0027FB22(cdi_fmvtest) TRAP[2689] #0 I$SetStt <= d0.w=4 d1.w=MA_Cntrl d2.w=1 d3.l=$42434445 d4.w=0
Effect is visible afterwards. According to this process, the attenuation is calculated on the DSP 56001 since the parameters are written into its memory space
@00E4FC40(madriv) WR.W 00E03022 <= 0000 [S] .DSPA
@00E4FC46(madriv) FMA DSP[MODE] <= 0080
@00E4FC46(madriv) WR.W 00E03024 <= 0080 [S] .DSPD
@00E4FC4C(madriv) WR.W 00E03022 <= 0001 [S] .DSPA
@00E4FC52(madriv) FMA DSP[TARGET] <= 0093
@00E4FC52(madriv) WR.W 00E03024 <= 0093 [S] .DSPD
@00E4FCE6(madriv) WR.W 00E03022 <= 0002 [S] .DSPA
@00E4FCEC(madriv) RD.W 00E03024 => 0004 [S]
@00E4FC5C(madriv) WR.W 00E03022 <= 0007 [S] .DSPA
@00E4FC70(madriv) WR.W 00E03024 <= 0044 [S] .DSPD <--
@00E4FCE6(madriv) WR.W 00E03022 <= 0002 [S] .DSPA
@00E4FCEC(madriv) RD.W 00E03024 => 0004 [S]
@00E4FC78(madriv) WR.W 00E03022 <= 0007 [S] .DSPA
@00E4FC8C(madriv) WR.W 00E03024 <= 0043 [S] .DSPD <--
@00E4FCE6(madriv) WR.W 00E03022 <= 0002 [S] .DSPA
@00E4FCEC(madriv) RD.W 00E03024 => 0004 [S]
@00E4FC94(madriv) WR.W 00E03022 <= 0007 [S] .DSPA
@00E4FCA8(madriv) WR.W 00E03024 <= 0045 [S] .DSPD <--
@00E4FCE6(madriv) WR.W 00E03022 <= 0002 [S] .DSPA
@00E4FCEC(madriv) RD.W 00E03024 => 0004 [S]
@00E4FCB0(madriv) WR.W 00E03022 <= 0007 [S] .DSPA
@00E4FCC4(madriv) FMA ATTEN <= 44434542
@00E4FCC4(madriv) WR.W 00E03024 <= 0042 [S] .DSPD <--
@00E4FCE6(madriv) WR.W 00E03022 <= 0002 [S] .DSPA
@00E4FCEC(madriv) RD.W 00E03024 => 0004 [S]
@00E4FCCC(madriv) WR.W 00E03022 <= 0000 [S] .DSPA
@00E4FCD2(madriv) FMA DSP[MODE] <= 00E2
@00E4FCD2(madriv) WR.W 00E03024 <= 00E2 [S] .DSPD
@00E4EDDE(madriv) FMA STAT => 0000
@00E4EDDE(madriv) RD.W 00E03002 => 0000 [S] .STAT
@00E4F838(madriv) FMA STAT => 0000
@00E4F838(madriv) RD.W 00E03002 => 0000 [S] .STAT
@00E4F840(madriv) WR.W 00D00032 <= 0000 [S] MA_STAT{ ASY_Stat=0 }
@00E4F846(madriv) WR.W 00D00032 <= 0000 [S] MA_STAT{ ASY_Stat=0 }
Notes about Robocop
The MPEG stream itself is 352 x 240 but the software decides to cut some pixels off.
@00E5276E(fmvdrv) FMV SCRPOS 00140000 (X=0,Y=20) @00E5276E(fmvdrv) WR.L 00E04074 <= 00140000 [S] .SCRPOS.SCRPOSYH @00E52784(fmvdrv) FMV DECWIN 00F00159 (W=345,H=240) @00E52784(fmvdrv) WR.L 00E04078 <= 00F00159 [S] .DECWIN.DECWINHH @00E5278C(fmvdrv) FMV DECOFF 00000007 (X=7,Y=0) @00E5278C(fmvdrv) WR.L 00E0407C <= 00000007 [S] .DECOFF.DECOFFYH
Resources
https://github.com/cdifan/cdichips?tab=readme-ov-file#mpeg-chips https://www.theworldofcdi.com/cd-i_encyclopedia/digital-video-cartridge/ https://www.icdia.co.uk/accesories/dv.html https://retrostuff.org/2017/02/12/the-7th-guest-cd-i-dvc-compatibility-cake-puzzle-bug/ https://opencores.org/projects/mpeg2fpga https://github.com/OldRepoPreservation/mpeg2fpga/ https://github.com/phoboslab/pl_mpeg http://dvdnav.mplayerhq.hu/dvdinfo/mpeghdrs.html https://ffmpeg.org/ffmpeg.html#Video-Options ffmpeg -h encoder=mpeg1video https://www.cs.cornell.edu/dali/overview/mpeg.html http://www.andrewduncan.net/mpeg/mpeg-1.html http://www.mp3-tech.org/programmer/frame_header.html https://www.cnblogs.com/JLMobile/articles/372075.html
http://www.mplayerhq.hu/DOCS/HTML/de/menc-feat-mpeg.html http://www.mplayerhq.hu/DOCS/HTML/de/menc-feat-vcd-dvd.html
@00E539BE(fmvdrv) FMV TIMECD => 000C0000 00:00:00.12 DROP=0 @00E539BE(fmvdrv) RD.L 00E04058 => 000C0000 [S] .TIMECD @00E539BE(fmvdrv) FMV TIMECD => 004B0000 00:00:01.11 DROP=0 @00E539BE(fmvdrv) RD.L 00E04058 => 004B0000 [S] .TIMECD @00E539BE(fmvdrv) FMV TIMECD => 01920000 00:00:06.18 DROP=0 @00E539BE(fmvdrv) RD.L 00E04058 => 01920000 [S] .TIMECD @00E539BE(fmvdrv) FMV TIMECD => 01C50000 00:00:07.05 DROP=0 @00E539BE(fmvdrv) RD.L 00E04058 => 01C50000 [S] .TIMECD
@00E51E5A(fmvdrv) FMV TIMECD => 04450003 00:03:17.05 DROP=0 @00E51E5A(fmvdrv) FMV TIMECD => 04130002 00:02:16.19 DROP=0 @00E51E5A(fmvdrv) FMV TIMECD => 08570002 00:02:33.23 DROP=0 @00E51E5A(fmvdrv) FMV TIMECD => 05C60007 00:07:23.06 DROP=0 @00E539BE(fmvdrv) FMV TIMECD => 00400007 00:07:01.00 DROP=0 @00E51E5A(fmvdrv) FMV TIMECD => 00520007 00:07:01.18 DROP=0
Example MPEG Audio Header:
11111111 11111101 FF FD Layer II MPEG Version 1 10110000 B0 224 kpbs Bitrate 44100 Hz Not padded 00000100 04 Stereo Copyrighted No emphasis 01110111 01010101 01000100 01100101
Frame Length
Layer I 384 samples Layer II 1152 samples
Interrupt Service Routine for FMV:
00e52e46 00002400 00000168 00000012 00000035 00000013 00dfd3d4 0040817c 008c2000 00e52e42 00dfee60 00dfb180 00e04000 00dfcc30 00dfd3e8 00001500 00dff350
A2 is 00dfb180 and should be the driver state A3 is 00e04000 which is the base of FMV registers
Memory Map
FMV (we have actually source code of this) 00e52944 PSOrg 00e5297c PSPos 00e52a50 PSWndw 00e52e46 IrqSrvc 00e52f54 UpdateSCR 00e52f5c PC inside UpdateSCR where D0 is V_BufStat(a2) 00e52ffe CheckSpeed 00e53052 CheckLevel 00e5312a HandleData 00e53312 H_DataExit (end of HandleData) 00e53318 NotReady 00e5333c CopyData 00e533ee WaitStart 00e535b4 HandleWaitS 00e536ee HandleFirst 00e53802 CopyPack 00e544b6 DecodTS 00e54546 Copy_It 00e54610 UpdPCLPtr 00e53d72 SendSignal
00dfb180 FMV Driver state (A2)
V_DataSize *(unsigned long*)(0x00dfb180 + 0x126)
V_Stat *(unsigned short*)(0x00dfb180 + 0x134)
V_BufStat *(unsigned char*)(0x00dfb180 + 0x17b)
V_ExtSCR *(unsigned long*)(0x00dfb180 + 0x154)
V_SCRF *(unsigned long*)(0x00dfb180 + 0x11c)
V_Count90 *(unsigned long*)(0x00dfb180 + 0x118)
V_SCR *(unsigned long*)(0x00dfb180 + 0xca)
V_CurDelta *(unsigned long*)(0x00dfb180 + 0x104)
V_NewDelta *(unsigned long*)(0x00dfb180 + 0x108)
V_SCRupd *(unsigned long*)(0x00dfb180 + 0x166)
V_Status *(unsigned short*)(0x00dfb180 + 0x136)
V_PICCnt *(unsigned char*)(0x00dfb180 + 0x1cd)
V_Scroll *(unsigned short*)(0x00dfb180 + 0x16a)
V_VCMD *(unsigned short*)(0x00dfb180 + 0x16c)
FMA (no source code available?)
00e4fe80 MA_Status
00e5029a MA_Play
00e502fe Stream Number transferred to register
00e504f0 IRQ Routine
00e5120c FMA Status 3002 is read here (ANDed with 0x38?)
00e50e6a DMA Transfer to FMA
00e511f6 OS9 Trap 0 for sending signals (good for tracing)
00dfb8f0 FMA Driver state? (A2)
00dfb3e0 FMA Driver state? (A2)
00dfb730 FMA Driver state? (A2)
long* (0x00,A2) Address of FMA (must be 00e03000) V_PORT
long* (0x30,A2) V_IRQMask
long* (0x8e,A2)
long* (0x96,A2) V_CurDesc ?
long* (0x9c,A2) V_PCL ?
long* (0xa0,A2) V_Offset ?
long* (0xa8,A2) V_EnLoop ?
word* (0xac,A2) V_LCntr ?
long* (0xb2,A2) V_LpStart ?
long* (0xbe,A2) V_CurAdr ? might be only relevant in host play
char* (0xc8,A2) V_Paused ?
char* (0xc9,A2) V_Sync ?
long* (0xca,A2) V_SCR ?
char* (0xfe,A2) V_Waste ?
long* (0x104,A2) V_CurDelta ? (used for SCR and PTS adjust)
long* (0x108,A2) V_NewDelta ? (never edited?)
long* (0x114,A2) ?
long* (0x118,A2) Subtracted from DCLK ?
short* (0x120,A2) Interrupt enable mirror (written to 0x301c)
long* (0x122,A2) DMA memory Address?
long* (0x126,A2) DMA something? Length in bytes?
short* (0x12a,A2) Written after DMA transfer. Written to ASY_SIG
char* (0x12c,A2) Some kind of SCR?
long* (0x12e,A2) DMA memory address for something of size 0xc?
char* (0x136,A2) ?
char* (0x137,A2) ?
char* (0x138,A2) ?
char* (0x139,A2) ?
char* (0x140,A2) ?
char* (0x13a,A2) ?
char* (0x13b,A2) ?
char* (0x13d,A2) ?
char* (0x140,A2) ?
long* (0x142,A2) Something with SCR? Subtract?
long* (0x14c,A2)
short* (0x150,A2) Interrupt state from 0x301a stored here
char* (0x152,A2)
long* (0x154,A2) DMA address for TransferMPEG in a special case?
char* (0x174,A2) Length for TransferMPEG in a special case?
V_BufStat
normal equ 1 slow equ 2 scanning equ 3 single equ 4 paused equ 5 frozen equ 6 decoding equ 7 stopped equ 8 stopping equ 9 waiting equ 10 released equ 11 error equ 12 reading equ 13 playing equ 14 idle equ 15 pausing equ 16
- The following values are only used in the V_BufStat field. waitfirst equ 32 0x20 operation seems to start here waitstart equ 33 0x21 set in StrtPlay? waitnormal equ 34 waitsector equ 35
Useful signaltap exe_pc adresses to catch
00e521fc PauseErr dez 15016444