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sampleconv: Improve WAV SMPL chunk handling, properly handle (#1862)

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odd chunk sizes

* Read WAV SMPL chunks for note info when INST chunks are not available

* Populate the SMPL chunk on conversion to wav

* Properly handle unaligned (odd) WAV chunk sizes
This commit is contained in:
Tharo
2026-03-09 11:32:36 +00:00
committed by GitHub
parent 826bc7588e
commit 02eafced87
2 changed files with 48 additions and 9 deletions
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tools/audio/sampleconv/src/container/container.h
+2 -2
View File
@@ -62,8 +62,8 @@ typedef struct container_data {
uint32_t num_samples; // also apparently called num_frames? but that's wrong
// Instrument details
int8_t base_note;
int8_t fine_tune;
int8_t base_note; // [0, 127]
int8_t fine_tune; // [-50, 50]
int8_t gain;
int8_t key_low;
int8_t key_hi;
tools/audio/sampleconv/src/container/wav.c
+46 -7
View File
@@ -221,6 +221,25 @@ wav_read(container_data *out, const char *path, UNUSED bool matching)
smpl.num_sample_loops = le32toh(smpl.num_sample_loops);
smpl.sampler_data = le32toh(smpl.sampler_data);
if (!has_inst) {
// No INST chunk (yet, if there is one later it will take priority)
// Read the base note and fine tuning from the SMPL chunk.
// Note the INST and SMPL chunk use different representations for the fine tuning
// INST uses cents in [-50, 50]
// SMPL uses a fraction [0, 255] with 128 = 50 cents
// We use the INST format since AIFF uses that one
uint32_t base_note = smpl.unity_note;
// First scale down 128 -> 50, round to nearest
int32_t fine_tune = (smpl.fine_tune * 50 + 0x40) / 128;
// If the result is > 50, make it negative and adjust the base note
if (fine_tune > 50) {
base_note = (base_note - 1) % 128;
fine_tune = fine_tune - 100;
}
out->base_note = base_note;
out->fine_tune = fine_tune;
}
out->num_loops = smpl.num_sample_loops;
out->loops = NULL;
if (out->num_loops != 0) {
@@ -342,13 +361,14 @@ wav_read(container_data *out, const char *path, UNUSED bool matching)
}
long read_size = ftell(in) - start - 8;
uint32_t aligned_chunk_size = (chunk_size + 1) & ~1;
if (read_size > chunk_size)
if (read_size > aligned_chunk_size)
error("overran chunk");
else if (!skipped && read_size < chunk_size)
warning("did not read entire %*s chunk: %lu vs %u", 4, cc4, read_size, chunk_size);
fseek(in, start + 8 + chunk_size, SEEK_SET);
fseek(in, start + 8 + aligned_chunk_size, SEEK_SET);
}
if (!has_fmt)
@@ -361,8 +381,10 @@ wav_read(container_data *out, const char *path, UNUSED bool matching)
}
if (!has_inst) {
out->base_note = 60; // C4
out->fine_tune = 0;
if (!has_smpl) {
out->base_note = 60; // C4
out->fine_tune = 0;
}
out->key_low = 0;
out->key_hi = 127;
out->vel_low = 0;
@@ -452,13 +474,30 @@ wav_write(container_data *in, const char *path, bool matching)
CHUNK_WRITE(out, &inst);
CHUNK_END(out, chunk_start, htole32);
// INST and SMPL use a different representation for the fine tuning.
// INST represents it in cents in the range [-50, 50]
// SMPL represents it as a fraction in the range [0, 255] where 128 is 50 cents
// Our internal fine tuning follows the INST format, which AIFF also happens to agree with.
// When writing SMPL we need to convert to the fraction representation, which for
// positive fine tuning is simply a rescaling, while for negative fine tuning we need to
// adjust the base note to make the fine tuning positive first.
uint32_t smpl_unity_note = in->base_note;
uint32_t smpl_fine_tune = in->fine_tune;
if (in->fine_tune < 0) {
// [-50, -1] needs to increment unity_note and use the additive inverse mod 100
smpl_unity_note = (smpl_unity_note + 1) % 128;
smpl_fine_tune = 100 + smpl_fine_tune;
}
// Rescale 0..50 to 0..128, round to nearest
smpl_fine_tune = (smpl_fine_tune * 128 + 25) / 50;
wav_smpl smpl = {
.manufacturer = 0,
.product = 0,
.sample_period = 0,
.unity_note = 0,
.sample_period = htole32(1000000000 / in->sample_rate),
.unity_note = htole32(smpl_unity_note),
._pad = {0, 0, 0},
.fine_tune = 0,
.fine_tune = smpl_fine_tune,
.format = 0,
.offset = 0,
.num_sample_loops = htole32(in->num_loops),