From 7548d5f7f9e9687260cd33b01bc382555fdbe73c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>
Date: Sat, 18 Jan 2014 13:56:28 +0100
Subject: [PATCH] openexrdec: Don't start scanning for the header from the
 start again each time

This will be incredible slow if the upstream block size is very small. Instead
continue scanning for the header where we previously stopped.

For the standard filesrc block-size this made decoding a file about
3 times faster.

https://bugzilla.gnome.org/show_bug.cgi?id=719890
---
 ext/openexr/gstopenexrdec.cpp | 38 +++++++++++++++++++++--------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/ext/openexr/gstopenexrdec.cpp b/ext/openexr/gstopenexrdec.cpp
index 54b5f5993d..d2d1dffce4 100644
--- a/ext/openexr/gstopenexrdec.cpp
+++ b/ext/openexr/gstopenexrdec.cpp
@@ -190,32 +190,38 @@ gst_openexr_dec_parse (GstVideoDecoder * decoder,
     GstVideoCodecFrame * frame, GstAdapter * adapter, gboolean at_eos)
 {
   guint8 data[8];
-  gsize size;
+  gsize size, parsed_size;
   guint32 magic, flags;
   gssize offset;
 
   size = gst_adapter_available (adapter);
 
+  parsed_size = gst_video_decoder_get_pending_frame_size (decoder);
+
   GST_DEBUG_OBJECT (decoder, "Parsing OpenEXR image data %" G_GSIZE_FORMAT,
       size);
 
-  if (size < 8)
+  if (parsed_size == 0 && size < 8)
     goto need_more_data;
 
-  gst_adapter_copy (adapter, data, 0, 8);
+  /* If we did not parse anything yet, check if the frame starts with the header */
+  if (parsed_size == 0) {
+    gst_adapter_copy (adapter, data, 0, 8);
 
-  magic = GST_READ_UINT32_LE (data);
-  flags = GST_READ_UINT32_LE (data + 4);
-  if (magic != 0x01312f76 || ((flags & 0xff) != 1 && (flags & 0xff) != 2) || ((flags & 0x200) && (flags & 0x1800))) {
-    offset = gst_adapter_masked_scan_uint32_peek (adapter, 0xffffffff, 0x762f3101, 0, size, NULL);
-    if (offset == -1) {
-      gst_adapter_flush (adapter, size - 4);
+    magic = GST_READ_UINT32_LE (data);
+    flags = GST_READ_UINT32_LE (data + 4);
+    if (magic != 0x01312f76 || ((flags & 0xff) != 1 && (flags & 0xff) != 2) || ((flags & 0x200) && (flags & 0x1800))) {
+      offset = gst_adapter_masked_scan_uint32_peek (adapter, 0xffffffff, 0x762f3101, 0, size, NULL);
+      if (offset == -1) {
+        gst_adapter_flush (adapter, size - 4);
+        goto need_more_data;
+      }
+
+      /* come back into this function after flushing some data */
+      gst_adapter_flush (adapter, offset);
       goto need_more_data;
     }
-
-    /* come back into this function after flushing some data */
-    gst_adapter_flush (adapter, offset);
-    goto need_more_data;
+  } else {
   }
 
   /* valid header, now let's try to find the next one unless we're EOS */
@@ -224,8 +230,10 @@ gst_openexr_dec_parse (GstVideoDecoder * decoder,
 
     while (!found) {
       offset = gst_adapter_masked_scan_uint32_peek (adapter, 0xffffffff, 0x762f3101, 8, size - 8 - 4, NULL);
-      if (offset == -1)
+      if (offset == -1) {        
+        gst_video_decoder_add_to_frame (decoder, size - 7);
         goto need_more_data;
+      }
 
       gst_adapter_copy (adapter, data, offset, 8);
       magic = GST_READ_UINT32_LE (data);
@@ -236,7 +244,7 @@ gst_openexr_dec_parse (GstVideoDecoder * decoder,
     size = offset;
   }
 
-  GST_DEBUG_OBJECT (decoder, "Have complete image of size %" G_GSSIZE_FORMAT, size);
+  GST_DEBUG_OBJECT (decoder, "Have complete image of size %" G_GSSIZE_FORMAT, size + parsed_size);
 
   gst_video_decoder_add_to_frame (decoder, size);