From a55d30c32f86c8ac7ba3222f3c6bdd7543c7d600 Mon Sep 17 00:00:00 2001
From: Jean-Marc Valin <jmvalin@jmvalin.ca>
Date: Mon, 6 Jun 2016 16:54:29 -0400
Subject: Don't use too much temporal resolution on hybrid frames at low rate

Otherwise, we risk having "temporal holes" in the HF that anti-collapse
can't always fill in.
---
 celt/celt_encoder.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/celt/celt_encoder.c b/celt/celt_encoder.c
index bee593b5..db41b390 100644
--- a/celt/celt_encoder.c
+++ b/celt/celt_encoder.c
@@ -1772,6 +1772,13 @@ int celt_encode_with_ec(CELTEncoder * OPUS_RESTRICT st, const opus_val16 * pcm,
       tf_select = tf_analysis(mode, effEnd, isTransient, tf_res, lambda, X, N, LM, &tf_sum, tf_estimate, tf_chan);
       for (i=effEnd;i<end;i++)
          tf_res[i] = tf_res[effEnd-1];
+   } else if (hybrid && effectiveBytes<15)
+   {
+      /* For low bitrate hybrid, we force temporal resolution to 5 ms rather than 2.5 ms. */
+      tf_sum = 0;
+      for (i=0;i<end;i++)
+         tf_res[i] = 0;
+      tf_select=isTransient;
    } else {
       tf_sum = 0;
       for (i=0;i<end;i++)
-- 
cgit v1.2.1