From 1e81bc4b64a9d383e5396869d14da6c2dff31f4d Mon Sep 17 00:00:00 2001
From: Vincent Penquerc'h <vincent.penquerch@collabora.co.uk>
Date: Mon, 21 Nov 2011 12:50:22 +0000
Subject: [PATCH] opusdec: read pre-skip from first header if available

---
 ext/opus/gstopusdec.c | 12 ++++++++++++
 ext/opus/gstopusdec.h |  1 +
 2 files changed, 13 insertions(+)

diff --git a/ext/opus/gstopusdec.c b/ext/opus/gstopusdec.c
index 54d25d56cd..f0a9a5144e 100644
--- a/ext/opus/gstopusdec.c
+++ b/ext/opus/gstopusdec.c
@@ -77,6 +77,8 @@ static GstFlowReturn gst_opus_dec_handle_frame (GstAudioDecoder * dec,
     GstBuffer * buffer);
 static gboolean gst_opus_dec_set_format (GstAudioDecoder * bdec,
     GstCaps * caps);
+static gboolean gst_opus_dec_is_header (GstBuffer * buf, const char *magic,
+    guint magic_size);
 
 static void
 gst_opus_dec_base_init (gpointer g_class)
@@ -122,6 +124,8 @@ gst_opus_dec_reset (GstOpusDec * dec)
 
   gst_buffer_replace (&dec->streamheader, NULL);
   gst_buffer_replace (&dec->vorbiscomment, NULL);
+
+  dec->pre_skip = 0;
 }
 
 static void
@@ -159,9 +163,17 @@ gst_opus_dec_stop (GstAudioDecoder * dec)
 static GstFlowReturn
 gst_opus_dec_parse_header (GstOpusDec * dec, GstBuffer * buf)
 {
+  g_return_val_if_fail (gst_opus_dec_is_header (buf, "OpusHead", 8),
+      GST_FLOW_ERROR);
+  g_return_val_if_fail (GST_BUFFER_SIZE (buf) >= 19, GST_FLOW_ERROR);
+
+  dec->pre_skip = GST_READ_UINT16_LE (GST_BUFFER_DATA (buf) + 10);
+  GST_DEBUG_OBJECT (dec, "Found pre-skip of %u samples", dec->pre_skip);
+
   return GST_FLOW_OK;
 }
 
+
 static GstFlowReturn
 gst_opus_dec_parse_comments (GstOpusDec * dec, GstBuffer * buf)
 {
diff --git a/ext/opus/gstopusdec.h b/ext/opus/gstopusdec.h
index 9e78330e1f..eee27dc554 100644
--- a/ext/opus/gstopusdec.h
+++ b/ext/opus/gstopusdec.h
@@ -53,6 +53,7 @@ struct _GstOpusDec {
 
   int sample_rate;
   int n_channels;
+  guint32 pre_skip;
 };
 
 struct _GstOpusDecClass {