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whisper: suppress hallucination and repetition loops across chunks #243

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60 changes: 58 additions & 2 deletions src/arch/whisper/model.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@
#include "transcribe-log.h"
#include "transcribe-meta.h"
#include "transcribe-prompting.h"
#include "transcribe-repetition-guard.h"
#include "weights.h"
#include "whisper.h"

Expand Down Expand Up @@ -1726,6 +1727,10 @@ transcribe_status whisper_run(transcribe_session * session,
// temperature was hot (>= 0.5). Init to the user knob; flipped at chunk end.
bool do_condition_on_prev_tokens = wp->condition_on_prev_tokens;

std::string last_emitted_text;
int64_t last_emitted_t1_ms = -1;
int consecutive_repeat_count = 0;

int seek = 0;
while (seek < total_mel_frames) {
if (cc->poll_abort()) {
Expand Down Expand Up @@ -2306,6 +2311,13 @@ transcribe_status whisper_run(transcribe_session * session,
}
consume_generated_token(next_id);

if (!generated_text_ids.empty() &&
transcribe::stop_on_repetition(generated_text_ids, "whisper step")) {
log_msg(TRANSCRIBE_LOG_LEVEL_INFO,
"whisper run: stopped repeating generation loop at step %d", step);
break;
}

if (n_past + 1 > static_cast<int>(n_ctx_decoder)) {
break;
}
Expand Down Expand Up @@ -2539,12 +2551,54 @@ transcribe_status whisper_run(transcribe_session * session,
// pairs" branch, full-chunk advance, no per-chunk segment emission.
WhisperSegmentResult seg_res = whisper_retrieve_segment(generated_ids, cm->tok, time_offset_ms, seek_num_frames,
want_segment_timestamps, timestamp_begin, vocab_size);
bool has_hallucination_in_chunk = false;
std::vector<transcribe_session::SegmentEntry> clean_segments;
clean_segments.reserve(seg_res.segments.size());

for (auto & seg : seg_res.segments) {
if (seg.text.empty()) {
continue;
}
bool is_hallucinated_repeat = false;
const bool is_consecutive_time = (last_emitted_t1_ms < 0 || (seg.t0_ms - last_emitted_t1_ms <= 15000));
if (!last_emitted_text.empty() && is_consecutive_time &&
(seg.text == last_emitted_text ||
(seg.text.size() >= 12 && last_emitted_text.size() >= 12 &&
(seg.text.find(last_emitted_text) != std::string::npos ||
last_emitted_text.find(seg.text) != std::string::npos)))) {
consecutive_repeat_count++;
if (consecutive_repeat_count >= 2 || (seg.text.size() >= 6 && consecutive_repeat_count >= 1)) {
is_hallucinated_repeat = true;
}
} else {
consecutive_repeat_count = 0;
last_emitted_text = seg.text;
last_emitted_t1_ms = seg.t1_ms;
}

if (is_hallucinated_repeat) {
has_hallucination_in_chunk = true;
log_msg(TRANSCRIBE_LOG_LEVEL_INFO,
"whisper run: suppressed repetitive hallucination [%.2fs - %.2fs]: %s",
seg.t0_ms / 1000.0, seg.t1_ms / 1000.0, seg.text.c_str());
continue;
}
clean_segments.push_back(std::move(seg));
}

for (auto & seg : clean_segments) {
cc->segments.push_back(std::move(seg));
}
int segment_offset_frames = seg_res.segment_offset_frames;
std::vector<std::vector<int32_t>> & prev_chunk_segments = seg_res.prev_chunk_segments;

if (has_hallucination_in_chunk) {
prev_chunk_segments.clear();
prev_history_segments.clear();
do_condition_on_prev_tokens = false;
segment_offset_frames = seek_num_frames;
}

// Update prev-context history from the _retrieve_segment slices, not
// accepted_generated_ids directly: the closed-pair branch discards the
// unfinished tail, and carrying it would leak into the next prompt.
Expand All @@ -2553,8 +2607,10 @@ transcribe_status whisper_run(transcribe_session * session,
prev_chunk_segments.end());
}

all_text_ids.insert(all_text_ids.end(), generated_text_ids.begin(), generated_text_ids.end());
all_raw_ids.insert(all_raw_ids.end(), generated_ids.begin(), generated_ids.end());
if (!has_hallucination_in_chunk) {
all_text_ids.insert(all_text_ids.end(), generated_text_ids.begin(), generated_text_ids.end());
all_raw_ids.insert(all_raw_ids.end(), generated_ids.begin(), generated_ids.end());
}

// Seek advance. HF (generation_whisper.py, 5.6.1) runs ONE seek loop
// for every input length — there is no separate short-form decode
Expand Down