Atrac3plus
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AT3+ Header Format
(*) Postulation
(**) Starting from the end of the offset.
| Offset | Name | Bits | Type | Semantics |
|---|---|---|---|---|
| 0x0 | magic | 32 | ASCII | "RIFF" magic |
| 0x4 | at3_size | 32 | le int | Total size of AT3 data** |
| 0x8 | magic | 32 | ASCII | "WAVE" magic |
| 0xC | magic | 32 | ASCII | "fmt " magic |
| 0x10 | wave_size | 32 | le int | Total size of wave format data** |
| 0x14 | format_type | 16 | le int | Type of format starting from FFFF going down (PCM is normally 1, so removing 1 from FFFF le = FEFF*) |
| 0x16 | channel_num | 16 | le int | Number of channels - 2 byte interger |
| 0x18 | sample_rate | 32 | le int | Sample Rate aka the number of samples per second. Common value is 44100 |
| 0x1C | bitrate | 32 | le int | The bitrate multiplied by 125/1000 (ex. 64768 bps*125/1000 = 8096) |
| 0x20 | frame_size | 32 | le int | The frame size of the corresponding bitrate. (bits per channel * number of channels)* |
| 0x24 | unk1 | 216 | le int | Unknown static hex (22 00 00 08 03 00 00 00 BF AA 23 E9 58 CB 71 44 A1 19 FF FA 01 E4 CE 62 01 00 28)* |
| 0x3F | unk3_bitrate | 8 | le int | It is bitrate specific. Maybe the -1 is to fit FF* (frame_size/8 - 1) |
| 0x40 | padding | 64 | - | 00 padding - 8 bytes |
| 0x48 | magic | 32 | ASCII | "fact" magic |
| 0x4C | fact_size | 32 | le int | Total size of fact data** |
| 0x50 | duration_ts | 32 | le int | The duration of the song in seconds accurate to microseconds multiplied by the sample rate (Song_duration(sec)*Sample_rate --> ex. 22.854014(s) * 44100 = duration_ts) |
| 0x54 | unk_fact_01 | 32 | le int | It is song specific (sample size?)* |
| 0x58 | magic | 32 | ASCII | "smpl" magic |
| 0x5C | smpl_size | 32 | le int | Total size of smpl data** |
| 0x60 | unk_smpl_01 | 352 | le int | Unknown static hex (00 00 00 00 00 00 00 00 94 58 00 00 3C 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01 00 00 00 18 00 00 00 00 00 00 00 00 00 00 00)* |
| 0x8C | unk_smpl_02 | 32 | le int | Start point of smpl loop.* Same as unk_fact_01 |
| 0x90 | unk_smpl_03 | 32 | le int | End point of smpl loop.* (duration_ts + (unk_fact_01 - 1)) |
| 0x94 | padding | 64 | - | 00 padding - 8 bytes |
| 0x9C | magic | 32 | ASCII | "data" magic |
| 0xA0 | data_size | 32 | le int | Total size of data** |
| 0xA4 | music_data | - | - | Presumably music data?* |
AT3 Bitrate Values (Information gathered only by experimenting on an AT3 with 2 Channels and a Sampling rate of 44100Hz)
| Bit-rate | 4 bytes le-int@0x1C | frame_size | 1 byte int@0x3F | Special Note |
|---|---|---|---|---|
| 48 kbps | 0x0000178D | 0x00000118 (280) | 0x22 | None |
| 64 kbps | 0x00001FA0 | 0x00000178 (376) | 0x2E | None |
| 66 kbps | 0x0000204D | 0x000000C0 | 0x?? | Has a Special Header (Invalid AT3+ bitrate) |
| 96 kbps | 0x00002F1B | 0x00000230 (560) | 0x45 | None |
| 105 kbps | 0x00003324 | 0x00000130 | 0x?? | Has a Special Header (Invalid AT3+ bitrate) |
| 128 kbps | 0x00003E95 | 0x000002E8 (744) | 0x5C | None |
| 132 kbps | 0x0000409A | 0x00000180 | 0x?? | Has a Special Header (Invalid AT3+ bitrate) |
| 160 kbps | 0x00004EBB | 0x000003A8 (936) | 0x74 | None |
| 192 kbps | 0x00005E35 | 0x00000460 (1120) | 0x8B | None |
| 256 kbps | 0x00007D29 | 0x000005D0 (1488) | 0xB9 | None |
| 320 kbps | 0x00009CCA | 0x00000748 (1864) | 0xE8 | None |
| 352 kbps | 0x0000AC44 | 0x00000800 (2048) | 0xFF | None |
