whisper : map token timestamps to original time when VAD is enabled

The segment timestamp getters already remap t0/t1 back to the original
audio timeline when VAD is used, but the per-token timestamps returned by
whisper_full_get_token_data() are left in VAD-processed time. That makes
word-level timing unusable with VAD, since tokens end up shifted by
however much silence was removed.

Add whisper_full_get_token_t0/t1 (and the _from_state variants) that run
the token times through the same vad_mapping_table the segment getters
use. With VAD off they just return the stored token times, so existing
callers are unaffected.

Author: linxiaodong

include/whisper.h

@@ -667,6 +667,14 @@ extern "C" {
     WHISPER_API whisper_token_data whisper_full_get_token_data           (struct whisper_context * ctx, int i_segment, int i_token);
     WHISPER_API whisper_token_data whisper_full_get_token_data_from_state(struct whisper_state * state, int i_segment, int i_token);
 
+    // Get the start/end time of the specified token in the specified segment
+    // When VAD is enabled these are mapped back to the original audio timeline,
+    // unlike whisper_full_get_token_data().t0/t1 which stay in VAD-processed time
+    WHISPER_API int64_t whisper_full_get_token_t0           (struct whisper_context * ctx, int i_segment, int i_token);
+    WHISPER_API int64_t whisper_full_get_token_t0_from_state(struct whisper_state * state, int i_segment, int i_token);
+    WHISPER_API int64_t whisper_full_get_token_t1           (struct whisper_context * ctx, int i_segment, int i_token);
+    WHISPER_API int64_t whisper_full_get_token_t1_from_state(struct whisper_state * state, int i_segment, int i_token);
+
     // Get the probability of the specified token in the specified segment
     WHISPER_API float whisper_full_get_token_p           (struct whisper_context * ctx, int i_segment, int i_token);
     WHISPER_API float whisper_full_get_token_p_from_state(struct whisper_state * state, int i_segment, int i_token);

src/whisper.cpp

@@ -8075,6 +8075,40 @@ struct whisper_token_data whisper_full_get_token_data(struct whisper_context * c
     return ctx->state->result_all[i_segment].tokens[i_token];
 }
 
+// Function to get the starting timestamp of a token
+int64_t whisper_full_get_token_t0_from_state(struct whisper_state * state, int i_segment, int i_token) {
+    const int64_t t0 = state->result_all[i_segment].tokens[i_token].t0;
+
+    // If VAD wasn't used, return the original timestamp
+    if (!state->has_vad_segments || state->vad_mapping_table.empty()) {
+        return t0;
+    }
+
+    // Map to original time using the mapping table
+    return map_processed_to_original_time(t0, state->vad_mapping_table);
+}
+
+int64_t whisper_full_get_token_t0(struct whisper_context * ctx, int i_segment, int i_token) {
+    return whisper_full_get_token_t0_from_state(ctx->state, i_segment, i_token);
+}
+
+// Function to get the ending timestamp of a token
+int64_t whisper_full_get_token_t1_from_state(struct whisper_state * state, int i_segment, int i_token) {
+    const int64_t t1 = state->result_all[i_segment].tokens[i_token].t1;
+
+    // If VAD wasn't used, return the original timestamp
+    if (!state->has_vad_segments || state->vad_mapping_table.empty()) {
+        return t1;
+    }
+
+    // Map to original time using the mapping table
+    return map_processed_to_original_time(t1, state->vad_mapping_table);
+}
+
+int64_t whisper_full_get_token_t1(struct whisper_context * ctx, int i_segment, int i_token) {
+    return whisper_full_get_token_t1_from_state(ctx->state, i_segment, i_token);
+}
+
 float whisper_full_get_token_p_from_state(struct whisper_state * state, int i_segment, int i_token) {
     return state->result_all[i_segment].tokens[i_token].p;
 }