From a98035d63580a4c6951affe6ddbb04315cffa75c Mon Sep 17 00:00:00 2001
From: Jim Broadus <jbroadus@gmail.com>
Date: Sat, 30 Jan 2021 22:05:21 -0800
Subject: [PATCH] transcoder: Separate suitable element search from creation

Split best element type search from Transcoder::CreateElementForMimeType
into new FindBestElementForMimeType method. This will allow the setting
dialog to determine the encoder element type before the pipeline is
built.
---
 src/transcoder/transcoder.cpp | 24 ++++++++++++++++--------
 src/transcoder/transcoder.h   |  5 +++++
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/src/transcoder/transcoder.cpp b/src/transcoder/transcoder.cpp
index af8fdb6dc..48168b85a 100644
--- a/src/transcoder/transcoder.cpp
+++ b/src/transcoder/transcoder.cpp
@@ -77,15 +77,13 @@ struct SuitableElement {
   int rank_;
 };
 
-GstElement* Transcoder::CreateElementForMimeType(const QString& element_type,
-                                                 const QString& mime_type,
-                                                 GstElement* bin) {
-  if (mime_type.isEmpty()) return nullptr;
+SuitableElement Transcoder::FindBestElementForMimeType(
+    const QString& element_type, const QString& mime_type) {
+  if (element_type.isEmpty() || mime_type.isEmpty()) return SuitableElement();
 
   // HACK: Force mp4mux because it doesn't set any useful src caps
   if (mime_type == "audio/mp4") {
-    LogLine(QString("Using '%1' (rank %2)").arg("mp4mux").arg(-1));
-    return CreateElement("mp4mux", bin);
+    return SuitableElement("mp4mux", -1);
   }
 
   // Keep track of all the suitable elements we find and figure out which
@@ -136,11 +134,21 @@ GstElement* Transcoder::CreateElementForMimeType(const QString& element_type,
   gst_plugin_feature_list_free(features);
   gst_caps_unref(target_caps);
 
-  if (suitable_elements_.isEmpty()) return nullptr;
+  if (suitable_elements_.isEmpty()) return SuitableElement();
 
   // Sort by rank
   std::sort(suitable_elements_.begin(), suitable_elements_.end());
-  const SuitableElement& best = suitable_elements_.last();
+  return suitable_elements_.last();
+}
+
+GstElement* Transcoder::CreateElementForMimeType(const QString& element_type,
+                                                 const QString& mime_type,
+                                                 GstElement* bin) {
+  SuitableElement best = FindBestElementForMimeType(element_type, mime_type);
+  if (best.name_.isEmpty()) {
+    LogLine(tr("Suitable element not found"));
+    return nullptr;
+  }
 
   LogLine(QString("Using '%1' (rank %2)").arg(best.name_).arg(best.rank_));
 
diff --git a/src/transcoder/transcoder.h b/src/transcoder/transcoder.h
index 138fefc9f..6d44ed443 100644
--- a/src/transcoder/transcoder.h
+++ b/src/transcoder/transcoder.h
@@ -29,6 +29,8 @@
 #include "core/song.h"
 #include "engines/gstpipelinebase.h"
 
+struct SuitableElement;
+
 struct TranscoderPreset {
   TranscoderPreset() : type_(Song::Type_Unknown) {}
   TranscoderPreset(Song::FileType type, const QString& name,
@@ -135,6 +137,9 @@ class Transcoder : public QObject {
                                        GstElement* bin = nullptr);
   void SetElementProperties(const QString& name, GObject* element);
 
+  static SuitableElement FindBestElementForMimeType(const QString& element_type,
+                                                    const QString& mime_type);
+
   static void NewPadCallback(GstElement*, GstPad* pad, gpointer data);
   static GstBusSyncReply BusCallbackSync(GstBus*, GstMessage* msg,
                                          gpointer data);