From b5ddb16ec77f53ffc7b017929f1cfb03a4b018c5 Mon Sep 17 00:00:00 2001
From: Georgi Gerganov <ggerganov@gmail.com>
Date: Mon, 23 Jan 2023 20:48:26 +0200
Subject: [PATCH] whisper : condition timestamps to be monotonically increasing
 (#425)

---
 whisper.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/whisper.cpp b/whisper.cpp
index d12cc4a..ef1608d 100644
--- a/whisper.cpp
+++ b/whisper.cpp
@@ -2988,6 +2988,16 @@ static void whisper_process_logits(
             }
         }
 
+        // condition timestamp tokens to be increasing
+        // ref: https://github.com/openai/whisper/pull/831#issuecomment-1385910556
+        if (decoder.has_ts) {
+            const int tid0 = decoder.seek_delta/2;
+
+            for (int i = vocab.token_beg; i < vocab.token_beg + tid0; ++i) {
+                logits[i] = -INFINITY;
+            }
+        }
+
         // populate the logprobs array (log_softmax)
         {
             const float logit_max = *std::max_element(logits.begin(), logits.end());