try to index media immediately on import

Since indexing is supplemental, it can be made a background task that can occur
at more or less any time. So we run it as soon as possible.

app/codec/decoder.cpp

@@ -26,6 +26,8 @@
 
 #include "codec/ffmpeg/ffmpegdecoder.h"
 #include "codec/oiio/oiiodecoder.h"
+#include "task/index/index.h"
+#include "task/taskmanager.h"
 
 Decoder::Decoder() :
   open_(false),
@@ -126,6 +128,14 @@ bool Decoder::ProbeMedia(Footage *f)
 
       // FIXME: Cache the results so we don't have to probe if this media is added a second time
 
+      // Start an index task
+      foreach (StreamPtr stream, f->streams()) {
+        qDebug() << "Starting index task on" << stream->footage()->filename() << stream->index();
+
+        IndexTask* index_task = new IndexTask(stream);
+        TaskManager::instance()->AddTask(index_task);
+      }
+
       return true;
     }
   }
@@ -161,3 +171,7 @@ void Decoder::Conform(const AudioRenderingParams &params)
   qCritical() << "Conform called on an audio decoder that does not have a handler for it:" << id();
   abort();
 }
+
+void Decoder::Index()
+{
+}

app/codec/decoder.h

@@ -219,6 +219,17 @@ public:
    */
   virtual void Conform(const AudioRenderingParams& params);
 
+  /**
+   * @brief Create an index for this media
+   *
+   * Indexes are used to improve speed and reliability of imported media. Calling Retrieve() will automatically check
+   * for an index and create one if it doesn't exist.
+   *
+   * Indexing is slow so it's recommended to do it in a background thread. Index() must be called while the Decoder is
+   * open, and does not automatically call Open() and Close() the Decoder. The caller must call thse manually.
+   */
+  virtual void Index();
+
 protected:
   bool open_;
 

app/codec/ffmpeg/ffmpegdecoder.cpp

@@ -62,6 +62,11 @@ bool FFmpegDecoder::Open()
     return true;
   }
 
+  if (!stream()) {
+    Error(QStringLiteral("Tried to open a decoder with no footage stream set"));
+    return false;
+  }
+
   int error_code;
 
   // Convert QString to a C string
@@ -344,7 +349,7 @@ FramePtr FFmpegDecoder::RetrieveAudio(const rational &timecode, const rational &
     return nullptr;
   }
 
-  ValidateIndex();
+  Index();
 
   Conform(params);
 
@@ -437,7 +442,7 @@ void FFmpegDecoder::Conform(const AudioRenderingParams &params)
     return;
   }
 
-  ValidateIndex();
+  Index();
 
   // Get indexed WAV file
   WaveInput input(GetIndexFilename());
@@ -659,7 +664,7 @@ bool FFmpegDecoder::Probe(Footage *f)
     Open();
 
     // Use index to find duration
-    ValidateIndex();
+    Index();
 
     // Use last frame index as the duration
     // FIXME: Does this skip the last frame?
@@ -706,17 +711,25 @@ void FFmpegDecoder::Index()
     return;
   }
 
-  // Reset state
-  Seek(0);
+  stream()->index_lock_.lock();
+
+  if (!LoadIndex()) {
+
+    // Reset state
+    Seek(0);
+
+    if (avstream_->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
+      IndexVideo(pkt_, frame_);
+    } else if (avstream_->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
+      IndexAudio(pkt_, frame_);
+    }
+
+    // Reset state
+    Seek(0);
 
-  if (avstream_->codecpar->codec_type == AVMEDIA_TYPE_VIDEO) {
-    IndexVideo(pkt_, frame_);
-  } else if (avstream_->codecpar->codec_type == AVMEDIA_TYPE_AUDIO) {
-    IndexAudio(pkt_, frame_);
   }
 
-  // Reset state
-  Seek(0);
+  stream()->index_lock_.unlock();
 }
 
 QString FFmpegDecoder::GetIndexFilename()
@@ -756,17 +769,6 @@ QString FFmpegDecoder::GetConformedFilename(const AudioRenderingParams &params)
   return index_fn;
 }
 
-void FFmpegDecoder::ValidateIndex()
-{
-  stream()->index_lock_.lock();
-
-  if (!LoadIndex()) {
-    Index();
-  }
-
-  stream()->index_lock_.unlock();
-}
-
 bool FFmpegDecoder::LoadIndex()
 {
   switch (avstream_->codecpar->codec_type) {
@@ -991,7 +993,7 @@ int64_t FFmpegDecoder::GetClosestTimestampInIndex(const int64_t &ts)
 {
   // Index now if we haven't already
   if (frame_index_.isEmpty()) {
-    ValidateIndex();
+    Index();
   }
 
   if (frame_index_.isEmpty()) {

app/codec/ffmpeg/ffmpegdecoder.h

@@ -92,18 +92,7 @@ private:
    */
   int GetFrame(AVPacket* pkt, AVFrame* frame);
 
-  /**
-   * @brief Create an index for this media
-   *
-   * Indexes are used to improve speed and reliability of imported media. Calling Retrieve() will automatically check
-   * for an index and create one if it doesn't exist.
-   *
-   * Indexing is slow so it's recommended to do it in a background thread. Index() must be called while the Decoder is
-   * open, and does not automatically call Open() and Close() the Decoder. The caller must call thse manually.
-   *
-   * FIXME: This should perhaps become a common function for the base Decoder class
-   */
-  void Index();
+  virtual void Index() override;
 
   /**
    * @brief Returns the filename for the index
@@ -117,8 +106,6 @@ private:
    */
   QString GetConformedFilename(const AudioRenderingParams &params);
 
-  void ValidateIndex();
-
   /**
    * @brief Used internally to load a frame index into frame_index_
    *