AY File Format
Here is a copy:
- AY-file format (thanks to Patrik Rak for help). Originally this format was supporting on Amiga's DeliTracker (DeliAY plug-in). Therefore, all word data is in Motorola order (from hi to lo). Also, all pointers are signed and relative (from current position in file to pointed data). So, AY-file is sequences of records. First record is header. Here you are: TAYFileHeader=packed record FileID, //'ZXAY' TypeID:longword; //'EMUL' FileVersion, //Version of song file (release version) PlayerVersion:byte; //Required player version. Micro Speccy //works as player of version 3. //Now available values: //0 Use zero, if you do not // know what player version // you need //All other player versions and short //description of these players next: //1 initial player version //2 first 256 bytes is // filled with 0xC9 (ret), // not just last init byte //3 PC rewrite, different // Z80 init routine, full // Z80 emulation, supports // 48k tunes. PSpecialPlayer, //It's for tunes which contained "custom //player" in m68k assembly. As Patrik Rak //is saying, exists only one AY-file of this //kind. So, can be simply ignored. PAuthor,PMisc:smallint; //Relative pointers to the //Author and Misc NTStrings NumOfSongs,FirstSong:byte; //Number of songs and first song values, both //are decreased by 1 PSongsStructure:smallint; //Relative pointer to song structure end; Next is song structure (repeated NumOfSongs + 1 times): TSongStructure=packed record PSongName,PSongData:smallint;//Relative pointers to NTStr song //name and song data end; All described above is rightly for any AY-file. Following data only for TypeID = 'EMUL'. Next is song data: TSongData=packed record AChan,BChan, CChan,Noise:byte; //These are actually four bytes which specify //which Amiga channels will play which AY //channel (A,B,C and Noise, respectively). The //legal value is any permutation of 0,1,2,3. //The most common is 0,1,2,3. Not used in //Micro Speccy, of course SongLength:word; //Song duration in 1/50 of second. If ZERO then //length is unknown (infinitely). Not used in //Micro Speccy FadeLength:word; //Duration of volume fade after end of song in //1/50 of second. Not used in Micro Speccy HiReg,LoReg:byte; //HiReg and LoReg for all common registers: //AF,AF',HL,HL',DE,DE',BC,BC',IX and IY PPoints, //Relative pointer to points data PAddresses:smallint; //Relative pointer to blocks data end; Next is points data: TPoints = packed record Stack,Init,Inter:word; //Values for SP, INIT and INTERRUPT addresses end; Next is blocks data (words, offsets are signed): Address1 //Address of 1st block in Z80 memory Length1 //Length of 1st block Offset1 //Relative offset in AY-file to this block Address2 //and for 2nd block Length2 Offset2 ... AddressN //and for Nth (last) block LengthN OffsetN ENDWORD //ZERO word (end of blocks data) //so block can't have ZERO //address Notes from Patrik Rak: The word values should be always aligned at 2 byte offsets. Otherwise the DeliAY will crash (it's the limitation of the m68000). In case Address+Length > 65536, DeliAY decreases the size to make it == 65536. From me: In case CurrPositionInAYFile+Offset+Length > AYFileSize, MicroSpeccy and AYPlay decreases the size to make it == AYFileSize. I must to say, that if it is then this is broken AY-file. But there are many that ones in the world. - How player of version 3 must play one of songs of AY File a) Fill #0000-#00FF range with #C9 value b) Fill #0100-#3FFF range with #FF value c) Fill #4000-#FFFF range with #00 value d) Place to #0038 address #FB value e) if INIT equal to ZERO then place to first CALL instruction address of first AY file block instead of INIT (see next f) and g) steps) f) if INTERRUPT equal to ZERO then place at ZERO address next player: DI CALL INIT LOOP: IM 2 EI HALT JR LOOP g) if INTERRUPT not equal to ZERO then place at ZERO address next player: DI CALL INIT LOOP: IM 1 EI HALT CALL INTERRUPT JR LOOP h) Load all blocks for this song i) Load all common lower registers with LoReg value (including AF register) j) Load all common higher registers with HiReg value k) Load into I register 3 (this player version) l) load to SP stack value from points data of this song m) Load to PC ZERO value n) Disable Z80 interrupts and set IM0 mode o) Emulate resetting of AY chip p) Start Z80 emulation As you can see, blocks of AY files can to rewrite standard player routine with own one. So, if you can not adapt some of tunes to standard player, you can write own player and place it at INIT address or even at 0x0001 address (block of AY-file can be loaded at any address except 0x0000).