Optimizes encoder NaN detection and clipping by only running them when needed

NaN detection should now be able to catch values that would create NaNs
further down.
diff --git a/celt/celt_encoder.c b/celt/celt_encoder.c
index ab28c8c..917f919 100644
--- a/celt/celt_encoder.c
+++ b/celt/celt_encoder.c
@@ -471,9 +471,8 @@
    coef0 = coef[0];
    m = *mem;
 
-#ifdef FIXED_POINT
-   /* Fast path for fixed-point in the normal 48kHz case */
-   if (coef[1] == 0 && upsample == 1)
+   /* Fast path for the normal 48kHz case and no clipping */
+   if (coef[1] == 0 && upsample == 1 && !clip)
    {
       for (i=0;i<N;i++)
       {
@@ -486,7 +485,6 @@
       *mem = m;
       return;
    }
-#endif
 
    Nu = N/upsample;
    if (upsample!=1)
@@ -495,17 +493,7 @@
          inp[i] = 0;
    }
    for (i=0;i<Nu;i++)
-   {
-      celt_sig x;
-
-      x = SCALEIN(pcmp[CC*i]);
-#ifndef FIXED_POINT
-      /* Replace NaNs with zeros */
-      if (!(x==x))
-         x = 0;
-#endif
-      inp[i*upsample] = x;
-   }
+      inp[i*upsample] = SCALEIN(pcmp[CC*i]);
 
 #ifndef FIXED_POINT
    if (clip)
@@ -1490,8 +1478,12 @@
       enc->nbits_total+=tell-ec_tell(enc);
    }
    c=0; do {
+      int need_clip=0;
+#ifndef FIXED_POINT
+      need_clip = st->clip && sample_max>65536.f;
+#endif
       celt_preemphasis(pcm+c, in+c*(N+st->overlap)+st->overlap, N, CC, st->upsample,
-                  mode->preemph, st->preemph_memE+c, st->clip);
+                  mode->preemph, st->preemph_memE+c, need_clip);
    } while (++c<CC);
 
 
diff --git a/src/opus_encoder.c b/src/opus_encoder.c
index fbd3de6..dc73a46 100644
--- a/src/opus_encoder.c
+++ b/src/opus_encoder.c
@@ -924,7 +924,8 @@
 
 opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_size,
                 unsigned char *data, opus_int32 out_data_bytes, int lsb_depth,
-                const void *analysis_pcm, opus_int32 analysis_size, int c1, int c2, int analysis_channels, downmix_func downmix)
+                const void *analysis_pcm, opus_int32 analysis_size, int c1, int c2,
+                int analysis_channels, downmix_func downmix, int float_api)
 {
     void *silk_enc;
     CELTEncoder *celt_enc;
@@ -1377,7 +1378,7 @@
              st->user_forced_mode = MODE_CELT_ONLY;
           tmp_len = opus_encode_native(st, pcm+i*(st->channels*st->Fs/50), st->Fs/50,
                 tmp_data+i*bytes_per_frame, bytes_per_frame, lsb_depth,
-                NULL, 0, c1, c2, analysis_channels, downmix);
+                NULL, 0, c1, c2, analysis_channels, downmix, float_api);
           if (tmp_len<0)
           {
              RESTORE_STACK;
@@ -1444,7 +1445,18 @@
     } else {
        dc_reject(pcm, 3, &pcm_buf[total_buffer*st->channels], st->hp_mem, frame_size, st->channels, st->Fs);
     }
-
+#ifndef FIXED_POINT
+    if (float_api)
+    {
+       opus_val32 sum=0;
+       for (i=0;i<frame_size*st->channels;i++)
+          sum += pcm_buf[total_buffer*st->channels+i]*pcm_buf[total_buffer*st->channels+i];
+       /* This should filter out both NaNs and ridiculous signals that could
+          cause NaNs further down. */
+       if (!(sum < 1e9))
+          OPUS_CLEAR(&pcm_buf[total_buffer*st->channels], frame_size*st->channels);
+    }
+#endif
 
 
     /* SILK processing */
@@ -1955,7 +1967,8 @@
 
    for (i=0;i<frame_size*st->channels;i++)
       in[i] = FLOAT2INT16(pcm[i]);
-   ret = opus_encode_native(st, in, frame_size, data, max_data_bytes, 16, pcm, analysis_frame_size, 0, -2, st->channels, downmix_float);
+   ret = opus_encode_native(st, in, frame_size, data, max_data_bytes, 16,
+                            pcm, analysis_frame_size, 0, -2, st->channels, downmix_float, 1);
    RESTORE_STACK;
    return ret;
 }
@@ -1977,7 +1990,8 @@
          , st->analysis.subframe_mem
 #endif
          );
-   return opus_encode_native(st, pcm, frame_size, data, out_data_bytes, 16, pcm, analysis_frame_size, 0, -2, st->channels, downmix_int);
+   return opus_encode_native(st, pcm, frame_size, data, out_data_bytes, 16,
+                             pcm, analysis_frame_size, 0, -2, st->channels, downmix_int, 0);
 }
 
 #else
@@ -2002,7 +2016,8 @@
 
    for (i=0;i<frame_size*st->channels;i++)
       in[i] = (1.0f/32768)*pcm[i];
-   ret = opus_encode_native(st, in, frame_size, data, max_data_bytes, 16, pcm, analysis_frame_size, 0, -2, st->channels, downmix_int);
+   ret = opus_encode_native(st, in, frame_size, data, max_data_bytes, 16,
+                            pcm, analysis_frame_size, 0, -2, st->channels, downmix_int, 0);
    RESTORE_STACK;
    return ret;
 }
@@ -2019,7 +2034,7 @@
          st->variable_duration, st->channels, st->Fs, st->bitrate_bps,
          delay_compensation, downmix_float, st->analysis.subframe_mem);
    return opus_encode_native(st, pcm, frame_size, data, out_data_bytes, 24,
-                             pcm, analysis_frame_size, 0, -2, st->channels, downmix_float);
+                             pcm, analysis_frame_size, 0, -2, st->channels, downmix_float, 1);
 }
 #endif
 
diff --git a/src/opus_multistream_encoder.c b/src/opus_multistream_encoder.c
index 49e2791..d6db70f 100644
--- a/src/opus_multistream_encoder.c
+++ b/src/opus_multistream_encoder.c
@@ -674,7 +674,8 @@
     unsigned char *data,
     opus_int32 max_data_bytes,
     int lsb_depth,
-    downmix_func downmix
+    downmix_func downmix,
+    int float_api
 )
 {
    opus_int32 Fs;
@@ -849,7 +850,7 @@
       if (!vbr && s == st->layout.nb_streams-1)
          opus_encoder_ctl(enc, OPUS_SET_BITRATE(curr_max*(8*Fs/frame_size)));
       len = opus_encode_native(enc, buf, frame_size, tmp_data, curr_max, lsb_depth,
-            pcm, analysis_frame_size, c1, c2, st->layout.nb_channels, downmix);
+            pcm, analysis_frame_size, c1, c2, st->layout.nb_channels, downmix, float_api);
       if (len<0)
       {
          RESTORE_STACK;
@@ -922,7 +923,7 @@
 )
 {
    return opus_multistream_encode_native(st, opus_copy_channel_in_short,
-      pcm, frame_size, data, max_data_bytes, 16, downmix_int);
+      pcm, frame_size, data, max_data_bytes, 16, downmix_int, 0);
 }
 
 #ifndef DISABLE_FLOAT_API
@@ -935,7 +936,7 @@
 )
 {
    return opus_multistream_encode_native(st, opus_copy_channel_in_float,
-      pcm, frame_size, data, max_data_bytes, 16, downmix_float);
+      pcm, frame_size, data, max_data_bytes, 16, downmix_float, 1);
 }
 #endif
 
@@ -951,7 +952,7 @@
 )
 {
    return opus_multistream_encode_native(st, opus_copy_channel_in_float,
-      pcm, frame_size, data, max_data_bytes, 24, downmix_float);
+      pcm, frame_size, data, max_data_bytes, 24, downmix_float, 1);
 }
 
 int opus_multistream_encode(
@@ -963,7 +964,7 @@
 )
 {
    return opus_multistream_encode_native(st, opus_copy_channel_in_short,
-      pcm, frame_size, data, max_data_bytes, 16, downmix_int);
+      pcm, frame_size, data, max_data_bytes, 16, downmix_int, 0);
 }
 #endif
 
diff --git a/src/opus_private.h b/src/opus_private.h
index 83225f2..2ab484b 100644
--- a/src/opus_private.h
+++ b/src/opus_private.h
@@ -104,7 +104,8 @@
 
 opus_int32 opus_encode_native(OpusEncoder *st, const opus_val16 *pcm, int frame_size,
       unsigned char *data, opus_int32 out_data_bytes, int lsb_depth,
-      const void *analysis_pcm, opus_int32 analysis_size, int c1, int c2, int analysis_channels, downmix_func downmix);
+      const void *analysis_pcm, opus_int32 analysis_size, int c1, int c2,
+      int analysis_channels, downmix_func downmix, int float_api);
 
 int opus_decode_native(OpusDecoder *st, const unsigned char *data, opus_int32 len,
       opus_val16 *pcm, int frame_size, int decode_fec, int self_delimited,