corrected switchnote speed

sppm-js/index.js

@@ -159,7 +159,7 @@ export async function readSppm(input, { legacyHmacKey = null } = {}) {
   r.take(4);
   const version = r.u16(), headerSize = r.u16(), totalBytes = r.u64(), expectedCrc = r.u32();
   const width = r.u16(), height = r.u16(), layerCount = r.u8(), paletteCount = r.u16(), fps = r.u8(), flags = r.u8(), frameCount = r.u32(), audioCount = r.u8(), reserved = r.u16();
-  if ((version !== 1 && version !== 2 && version !== 3) || headerSize !== HEADER_SIZE || totalBytes !== body.length || width !== WIDTH || height !== HEIGHT || layerCount !== 4 || paletteCount !== 256 || fps < 1 || fps > 30 || frameCount < 1 || frameCount > 9999 || audioCount > 4 || reserved !== 0 || ((version === 1 ? flags & ~3 : flags & ~15) !== 0)) fail("unsupported SPPM header");
+  if ((version !== 1 && version !== 2 && version !== 3) || headerSize !== HEADER_SIZE || totalBytes !== body.length || width !== WIDTH || height !== HEIGHT || layerCount !== 4 || paletteCount !== 256 || fps < 1 || fps > 30 || frameCount < 1 || frameCount > 9999 || audioCount > 4 || (version < 3 ? reserved !== 0 : reserved > 8) || ((version === 1 ? flags & ~3 : flags & ~15) !== 0)) fail("unsupported SPPM header");
   if (crc32(body.subarray(HEADER_SIZE)) !== expectedCrc) fail("payload CRC mismatch");
 
   const paletteBytes = r.take(256 * 4), palette = new Array(256);
@@ -167,7 +167,9 @@ export async function readSppm(input, { legacyHmacKey = null } = {}) {
   const metadata = {
     title: r.string(256), description: r.string(4096), authorName: r.string(128), originalAuthorName: r.string(128), lastEditorName: r.string(128),
     authorFsid: r.id(), originalAuthorFsid: r.id(), lastEditorFsid: r.id(), currentId: r.id(), rootId: r.id(), parentId: r.id(true),
-    createdUnixSeconds: r.u64(), modifiedUnixSeconds: r.u64(), coverFrame: r.u32(), width, height, fps,
+    createdUnixSeconds: r.u64(), modifiedUnixSeconds: r.u64(), coverFrame: r.u32(), width, height,
+    speed: version >= 3 ? reserved : 0, nominalFps: fps,
+    fps: version >= 3 && reserved >= 1 ? [0, 0.4985, 1, 2, 4, 5.9972, 11.986, 19.9459, 29.9275][reserved] : fps,
     locked: !!(flags & 1), allowSpinoffs: !!(flags & 2), bgmFollowsSpeed: version === 1 || !!(flags & 4), loopPlayback: version === 1 ? true : !(flags & 8),
     frameCount, audioTrackCount: audioCount, formatVersion: version, signature: signature.status,
   };
@@ -201,7 +203,7 @@ export async function readSppm(input, { legacyHmacKey = null } = {}) {
   const audioTracks = [];
   let audioSamples = 0;
   for (let ti = 0; ti < audioCount; ti++) {
-    const index = r.u8(), channels = r.u8(), referenceFps = version >= 2 ? r.u8() : 0, sampleRate = r.u32(), name = r.string(64), triggerCount = r.u16();
+    const index = r.u8(), channels = r.u8(), storedReference = version >= 2 ? r.u8() : 0, sampleRate = r.u32(), name = r.string(64), triggerCount = r.u16();
     if (index !== ti || (channels !== 1 && channels !== 2) || sampleRate < 8000 || sampleRate > 48000 || triggerCount > frameCount || (ti === 0 && triggerCount !== 0)) fail("invalid audio metadata");
     const triggers = Array.from({ length: triggerCount }, () => r.u16());
     for (let i = 0; i < triggers.length; i++) if (triggers[i] >= frameCount || (i && triggers[i] <= triggers[i - 1])) fail("invalid sound-effect frame cues");
@@ -212,7 +214,10 @@ export async function readSppm(input, { legacyHmacKey = null } = {}) {
     const pcm = new Int16Array(sampleCount);
     const sampleView = new DataView(pcmBytes.buffer, pcmBytes.byteOffset, pcmBytes.byteLength);
     for (let i = 0; i < sampleCount; i++) pcm[i] = sampleView.getInt16(i * 2, true);
-    audioTracks.push({ index, name, channels, referenceFps: ti === 0 && version === 1 ? fps : referenceFps, sampleRate, frameTriggers: triggers, pcm });
+    const referenceSpeed = version >= 3 && reserved !== 0 && ti === 0 ? storedReference : 0;
+    const referenceFps = version >= 3 && reserved !== 0 ? 0 : ti === 0 && version === 1 ? fps : storedReference;
+    if (version >= 3 && reserved !== 0 && (ti === 0 ? storedReference > 8 : storedReference !== 0)) fail("invalid audio speed metadata");
+    audioTracks.push({ index, name, channels, referenceFps, referenceSpeed, sampleRate, frameTriggers: triggers, pcm });
   }
   if (r.at !== body.length) fail("unexpected trailing bytes");
   return { width, height, palette, metadata, frames, audioTracks, signature };
@@ -333,7 +338,7 @@ export class SppmPlayer {
       }
       if (track.index === 0) {
         const source = this.audioContext.createBufferSource(); source.buffer = buffer;
-        if (this.note.metadata.bgmFollowsSpeed) source.playbackRate.value = fps / (track.referenceFps || fps);
+        if (this.note.metadata.bgmFollowsSpeed) source.playbackRate.value = fps / (track.referenceSpeed ? [0, 0.4985, 1, 2, 4, 5.9972, 11.986, 19.9459, 29.9275][track.referenceSpeed] : (track.referenceFps || fps));
         source.loop = !!this.loop; source.connect(this.audioContext.destination); source.start(start); this.sources.push(source);
       } else for (const cue of track.frameTriggers) {
         const source = this.audioContext.createBufferSource(); source.buffer = buffer; source.connect(this.audioContext.destination);

sppm-js/test/sppm.test.js

@@ -7,14 +7,14 @@ function crc32(bytes) {
   for (const b of bytes) { crc ^= b; for (let i = 0; i < 8; i++) crc = (crc >>> 1) ^ ((crc & 1) ? 0xedb88320 : 0); }
   return (crc ^ 0xffffffff) >>> 0;
 }
-function fixture() {
+function fixture(version = 2, speed = 0) {
   const parts = [];
   const u8 = n => parts.push(Buffer.from([n & 255]));
   const u16 = n => { const b = Buffer.alloc(2); b.writeUInt16LE(n); parts.push(b); };
   const u32 = n => { const b = Buffer.alloc(4); b.writeUInt32LE(n); parts.push(b); };
   const u64 = n => { const b = Buffer.alloc(8); b.writeBigUInt64LE(BigInt(n)); parts.push(b); };
   const str = s => { const b = Buffer.from(s); u16(b.length); parts.push(b); };
-  parts.push(Buffer.from("SPPM")); u16(2); u16(36); u64(0); u32(0); u16(640); u16(360); u8(4); u16(256); u8(12); u8(2); u32(1); u8(0); u16(0);
+  parts.push(Buffer.from("SPPM")); u16(version); u16(36); u64(0); u32(0); u16(640); u16(360); u8(4); u16(256); u8(12); u8(2); u32(1); u8(0); u16(speed);
   const palette = Buffer.alloc(1024); palette.set([255, 0, 0, 255], 4); parts.push(palette);
   ["JS fixture", "", "Tester", "Tester", "Tester"].forEach(str);
   ["1111111111111111", "1111111111111111", "1111111111111111", "2222222222222222", "2222222222222222", "0000000000000000"].forEach(id => parts.push(Buffer.from(id)));
@@ -45,3 +45,11 @@ test("rejects damaged payload CRC", async () => {
   const bytes = fixture(); bytes[80] ^= 1;
   await assert.rejects(readSppm(bytes), /CRC/);
 });
+
+test("reads DSi speed indices using the measured frame rates", async () => {
+  const bytes = fixture(3, 1);
+  const note = await readSppm(bytes);
+  assert.equal(note.metadata.speed, 1);
+  assert.equal(note.metadata.fps, 0.4985);
+  assert.equal(note.metadata.nominalFps, 12);
+});

sppm-python/sppm_tools.py

@@ -40,6 +40,7 @@ class AudioTrack:
     name: str
     frame_triggers: list[int]
     pcm: array.array
+    reference_speed: int = 0
 
 
 @dataclass
@@ -208,7 +209,7 @@ def read_sppm(source: Input, *, legacy_hmac_key: Optional[bytes] = None) -> Sppm
     frame_count, audio_count, reserved = r.u32(), r.u8(), r.u16()
     if (version not in (1, 2, 3) or header_size != HEADER_SIZE or total_size != len(body) or
         width != WIDTH or height != HEIGHT or layer_count != 4 or palette_count != 256 or
-        not 1 <= fps <= 30 or not 1 <= frame_count <= 9999 or audio_count > 4 or reserved != 0 or
+        not 1 <= fps <= 30 or not 1 <= frame_count <= 9999 or audio_count > 4 or (reserved != 0 if version < 3 else reserved > 8) or
         (flags & ~(3 if version == 1 else 15))):
         raise SppmError("unsupported SPPM header")
     if zlib.crc32(body[HEADER_SIZE:]) & 0xFFFFFFFF != expected_crc:
@@ -228,7 +229,10 @@ def read_sppm(source: Input, *, legacy_hmac_key: Optional[bytes] = None) -> Sppm
         "authorFsid": r.id(), "originalAuthorFsid": r.id(), "lastEditorFsid": r.id(),
         "currentId": r.id(), "rootId": r.id(), "parentId": r.id(True),
         "createdUnixSeconds": r.u64(), "modifiedUnixSeconds": r.u64(), "coverFrame": r.u32(),
-        "width": width, "height": height, "fps": fps, "locked": bool(flags & 1),
+        "width": width, "height": height,
+        "speed": reserved if version >= 3 else 0, "nominalFps": fps,
+        "fps": (0.4985, 1.0, 2.0, 4.0, 5.9972, 11.986, 19.9459, 29.9275)[reserved - 1] if version >= 3 and reserved else fps,
+        "locked": bool(flags & 1),
         "allowSpinoffs": bool(flags & 2), "bgmFollowsSpeed": version == 1 or bool(flags & 4),
         "loopPlayback": True if version == 1 else not bool(flags & 8),
         "frameCount": frame_count, "audioTrackCount": audio_count, "formatVersion": version,
@@ -280,8 +284,12 @@ def read_sppm(source: Input, *, legacy_hmac_key: Optional[bytes] = None) -> Sppm
         pcm.frombytes(raw_pcm)
         if struct.pack("=H", 1) != b"\x01\x00":
             pcm.byteswap()
-        tracks.append(AudioTrack(index, channels, fps if ti == 0 and version == 1 else reference_fps,
-                                 sample_rate, name, cues, pcm))
+        reference_speed = reference_fps if version >= 3 and reserved != 0 and ti == 0 else 0
+        if version >= 3 and reserved != 0 and (reference_speed > 8 or (ti > 0 and reference_fps != 0)):
+            raise SppmError("invalid audio speed metadata")
+        legacy_reference_fps = (fps if ti == 0 else reference_fps) if version < 3 or reserved == 0 else 0
+        tracks.append(AudioTrack(index, channels, legacy_reference_fps,
+                                 sample_rate, name, cues, pcm, reference_speed))
     if r.at != body_end:
         raise SppmError("unexpected trailing bytes")
     return SppmNote(meta, palette, frames, tracks, signature)
@@ -358,7 +366,9 @@ def _mix_wav(note: SppmNote, wav_path: str, sample_rate: int = 48000, chunk_seco
             times = (base + np.arange(count, dtype=np.float64)) / sample_rate
             for track, source in sources:
                 if track.index == 0:
-                    rate = track.sample_rate * (fps / (track.reference_fps or fps) if note.metadata["bgmFollowsSpeed"] else 1.0)
+                    reference_fps = ((0.4985, 1.0, 2.0, 4.0, 5.9972, 11.986, 19.9459, 29.9275)[track.reference_speed - 1]
+                                     if track.reference_speed else (track.reference_fps or fps))
+                    rate = track.sample_rate * (fps / reference_fps if note.metadata["bgmFollowsSpeed"] else 1.0)
                     positions = times * rate
                     valid = np.ones(count, dtype=bool) if note.metadata["loopPlayback"] else positions < len(source)
                     if note.metadata["loopPlayback"]:

sppm-python/test_sppm_tools.py

@@ -9,7 +9,7 @@ from pathlib import Path
 from sppm_tools import get_sppm_metadata, get_sppm_thumbnail, read_sppm, sppm_to_mp4
 
 
-def fixture() -> bytes:
+def fixture(version: int = 2, speed: int = 0) -> bytes:
     payload = bytearray()
     palette = bytearray(256 * 4)
     palette[4:8] = bytes((255, 0, 0, 255))
@@ -37,15 +37,15 @@ def fixture() -> bytes:
         payload.extend(encoded)
 
     pcm = struct.pack("<800h", *([1200, -1200] * 400))
-    payload.extend(struct.pack("<BBB I", 0, 1, 12, 8000))
+    payload.extend(struct.pack("<BBB I", 0, 1, (6 if version >= 3 and speed else 12), 8000))
     text("BGM")
     payload.extend(struct.pack("<HII", 0, 800, zlib.crc32(pcm) & 0xffffffff))
     payload.extend(pcm)
 
     header = bytearray(b"SPPM")
-    header.extend(struct.pack("<HHQ I HH B H B B I B H", 2, 36, 36 + len(payload),
+    header.extend(struct.pack("<HHQ I HH B H B B I B H", version, 36, 36 + len(payload),
                               zlib.crc32(payload) & 0xffffffff, 640, 360, 4, 256,
-                              12, 2, 1, 1, 0))
+                              12, 2, 1, 1, speed))
     assert len(header) == 36
     return bytes(header + payload)
 
@@ -75,6 +75,12 @@ class SppmToolTests(unittest.TestCase):
         with self.assertRaisesRegex(ValueError, "CRC"):
             read_sppm(broken)
 
+    def test_reads_dsi_speed_indices_using_measured_rates(self):
+        note = read_sppm(fixture(version=3, speed=1))
+        self.assertEqual(note.metadata["speed"], 1)
+        self.assertEqual(note.metadata["fps"], 0.4985)
+        self.assertEqual(note.audio_tracks[0].reference_speed, 6)
+
 
 if __name__ == "__main__":
     unittest.main()