Importer functions return a vector of vector of pointers to tracks...

... grouping the channels; rather than one flat vector.

OGG, GStreamer and FFmpeg import were written to allow multiple multi-channel
tracks; others always imported one group of channels.

All of that is reflected in the results returned by the importers, though it
makes no difference yet in AudacityProject::AddImportedTracks (where the
results are used).

src/Project.cpp

@@ -4168,7 +4168,6 @@ AudacityProject::AddImportedTracks(const wxString &fileName,
 {
    std::vector< std::shared_ptr< Track > > results;
 
-   const auto numTracks = newTracks.size();
    SelectNone();
 
    bool initiallyEmpty = mTracks->empty();
@@ -4177,9 +4176,11 @@ AudacityProject::AddImportedTracks(const wxString &fileName,
    int i = -1;
 
    // Must add all tracks first (before using Track::IsLeader)
-   for (auto &uNewTrack : newTracks) {
-      auto newTrack = mTracks->Add(std::move(uNewTrack));
-      results.push_back(Track::Pointer(newTrack));
+   for (auto &group : newTracks) {
+      for (auto &uNewTrack : group) {
+         auto newTrack = mTracks->Add(std::move(uNewTrack));
+         results.push_back(Track::Pointer(newTrack));
+      }
    }
    newTracks.clear();
       

src/import/Import.cpp

@@ -49,6 +49,7 @@ and ImportLOF.cpp.
 #include <wx/listimpl.cpp>
 #include "../ShuttleGui.h"
 #include "../Project.h"
+#include "../WaveTrack.h"
 
 #include "ImportPCM.h"
 #include "ImportMP3.h"
@@ -538,6 +539,15 @@ bool Importer::Import(const wxString &fName,
                return true;
             }
 
+            auto end = tracks.end();
+            auto iter = std::remove_if( tracks.begin(), end,
+               std::mem_fn( &NewChannelGroup::empty ) );
+            if ( iter != end ) {
+               // importer shouldn't give us empty groups of channels!
+               wxASSERT(false);
+               // But correct that and proceed anyway
+               tracks.erase( iter, end );
+            }
             if (tracks.size() > 0)
             {
                // success!

src/import/ImportFFmpeg.cpp

@@ -274,7 +274,10 @@ private:
    bool                  mCancelled;     //!< True if importing was canceled by user
    bool                  mStopped;       //!< True if importing was stopped by user
    wxString              mName;
-   std::list<TrackHolders> mChannels;     //!< 2-dimentional array of WaveTrack's. First dimention - streams, second - channels of a stream. Length is mNumStreams
+   TrackHolders mChannels;               //!< 2-dimensional array of WaveTrack's.
+                                         //!< First dimension - streams,
+                                         //!< second - channels of a stream.
+                                         //!< Length is mNumStreams
 #ifdef EXPERIMENTAL_OD_FFMPEG
    bool                  mUsingOD;
 #endif
@@ -688,13 +691,10 @@ ProgressResult FFmpegImportFileHandle::Import(TrackFactory *trackFactory,
 
    // Copy audio from mChannels to newly created tracks (destroying mChannels elements in process)
    for (auto &stream : mChannels)
-   {
       for(auto &channel : stream)
-      {
          channel->Flush();
-         outTracks.push_back(std::move(channel));
-      }
-   }
+
+   outTracks.swap(mChannels);
 
    // Save metadata
    WriteMetadata(tags);

src/import/ImportFLAC.cpp

@@ -181,7 +181,7 @@ private:
    FLAC__uint64          mSamplesDone;
    bool                  mStreamInfoDone;
    ProgressResult        mUpdateResult;
-   TrackHolders          mChannels;
+   NewChannelGroup       mChannels;
    std::unique_ptr<ODDecodeFlacTask> mDecoderTask;
 };
 
@@ -536,10 +536,11 @@ ProgressResult FLACImportFileHandle::Import(TrackFactory *trackFactory,
       return mUpdateResult;
    }
 
-   for (const auto &channel : mChannels) {
+   for (const auto &channel : mChannels)
       channel->Flush();
-   }
-   outTracks.swap(mChannels);
+
+   if (!mChannels.empty())
+      outTracks.push_back(std::move(mChannels));
 
    tags->Clear();
    size_t cnt = mFile->mComments.GetCount();

src/import/ImportGStreamer.cpp

@@ -130,7 +130,7 @@ struct GStreamContext
    GstElement    *mConv{};         // Audio converter
    GstElement    *mSink{};         // Application sink
    bool           mUse{};          // True if this stream should be imported
-   TrackHolders   mChannels;     // Array of WaveTrack pointers, one for each channel
+   NewChannelGroup mChannels;     // Array of WaveTrack pointers, one for each channel
    unsigned       mNumChannels{};  // Number of channels
    gdouble        mSampleRate{};   // Sample rate
    GstString      mType;         // Audio type
@@ -1140,18 +1140,6 @@ GStreamerImportFileHandle::Import(TrackFactory *trackFactory,
    // Grab the streams lock
    g_mutex_locker locker{ mStreamsLock };
 
-   // Count the total number of tracks collected
-   unsigned outNumTracks = 0;
-   for (guint s = 0; s < mStreams.size(); s++)
-   {
-      GStreamContext *c = mStreams[s].get();
-      if (c)
-         outNumTracks += c->mNumChannels;
-   }
-
-   // Create NEW tracks
-   outTracks.resize(outNumTracks);
-
    // Copy audio from mChannels to newly created tracks (destroying mChannels in process)
    int trackindex = 0;
    for (guint s = 0; s < mStreams.size(); s++)
@@ -1160,12 +1148,8 @@ GStreamerImportFileHandle::Import(TrackFactory *trackFactory,
       if (c->mNumChannels)
       {
          for (int ch = 0; ch < c->mNumChannels; ch++)
-         {
             c->mChannels[ch]->Flush();
-            outTracks[trackindex++] = std::move(c->mChannels[ch]);
-         }
-
-         c->mChannels.clear();
+         outTracks.push_back(std::move(c->mChannels));
       }
    }
 

src/import/ImportLOF.cpp

@@ -223,8 +223,9 @@ auto LOFImportFileHandle::GetFileUncompressedBytes() -> ByteCount
    return 0;
 }
 
-ProgressResult LOFImportFileHandle::Import(TrackFactory * WXUNUSED(trackFactory), TrackHolders &outTracks,
-                                Tags * WXUNUSED(tags))
+ProgressResult LOFImportFileHandle::Import(
+   TrackFactory * WXUNUSED(trackFactory), TrackHolders &outTracks,
+   Tags * WXUNUSED(tags))
 {
    // Unlike other ImportFileHandle subclasses, this one never gives any tracks
    // back to the caller.

src/import/ImportMP3.cpp

@@ -98,7 +98,7 @@ struct private_data {
    ArrayOf<unsigned char> inputBuffer{ static_cast<unsigned int>(INPUT_BUFFER_SIZE) };
    int inputBufferFill;     /* amount of data in inputBuffer */
    TrackFactory *trackFactory;
-   TrackHolders channels;
+   NewChannelGroup channels;
    ProgressDialog *progress;
    unsigned numChannels;
    ProgressResult updateResult;
@@ -208,8 +208,9 @@ auto MP3ImportFileHandle::GetFileUncompressedBytes() -> ByteCount
    return 0;
 }
 
-ProgressResult MP3ImportFileHandle::Import(TrackFactory *trackFactory, TrackHolders &outTracks,
-                                Tags *tags)
+ProgressResult MP3ImportFileHandle::Import(
+   TrackFactory *trackFactory, TrackHolders &outTracks,
+   Tags *tags)
 {
    outTracks.clear();
 
@@ -252,7 +253,8 @@ ProgressResult MP3ImportFileHandle::Import(TrackFactory *trackFactory, TrackHold
    for(const auto &channel : privateData.channels) {
       channel->Flush();
    }
-   outTracks.swap(privateData.channels);
+   if (!privateData.channels.empty())
+      outTracks.push_back(std::move(privateData.channels));
 
    /* Read in any metadata */
    ImportID3(tags);

src/import/ImportOGG.cpp

@@ -155,7 +155,7 @@ private:
 
    ArrayOf<int> mStreamUsage;
    wxArrayString   mStreamInfo;
-   std::list<TrackHolders> mChannels;
+   std::list<NewChannelGroup> mChannels;
 
    sampleFormat   mFormat;
 };
@@ -228,7 +228,8 @@ auto OggImportFileHandle::GetFileUncompressedBytes() -> ByteCount
    return 0;
 }
 
-ProgressResult OggImportFileHandle::Import(TrackFactory *trackFactory, TrackHolders &outTracks,
+ProgressResult OggImportFileHandle::Import(
+   TrackFactory *trackFactory, TrackHolders &outTracks,
    Tags *tags)
 {
    outTracks.clear();
@@ -374,10 +375,9 @@ ProgressResult OggImportFileHandle::Import(TrackFactory *trackFactory, TrackHold
 
    for (auto &link : mChannels)
    {
-      for (auto &channel : link) {
+      for (auto &channel : link)
          channel->Flush();
-         outTracks.push_back(std::move(channel));
-      }
+      outTracks.push_back(std::move(link));
    }
 
    //\todo { Extract comments from each stream? }

src/import/ImportPCM.cpp

@@ -364,7 +364,7 @@ ProgressResult PCMImportFileHandle::Import(TrackFactory *trackFactory,
 
    CreateProgress();
 
-   TrackHolders channels(mInfo.channels);
+   NewChannelGroup channels(mInfo.channels);
 
    auto iter = channels.begin();
    for (int c = 0; c < mInfo.channels; ++iter, ++c) {
@@ -529,10 +529,11 @@ ProgressResult PCMImportFileHandle::Import(TrackFactory *trackFactory,
       return updateResult;
    }
 
-   for(const auto &channel : channels) {
+   for(const auto &channel : channels)
       channel->Flush();
-   }
-   outTracks.swap(channels);
+
+   if (!channels.empty())
+      outTracks.push_back(std::move(channels));
 
    const char *str;
 

src/import/ImportPlugin.h

@@ -157,6 +157,8 @@ public:
    // The given Tags structure may also be modified.
    // In case of errors or exceptions, it is not necessary to leave outTracks
    // or tags unmodified.
+   // If resulting outTracks is not empty,
+   // then each member of it must be a nonempty vector.
    virtual ProgressResult Import(TrackFactory *trackFactory, TrackHolders &outTracks,
                       Tags *tags) = 0;
 

src/import/ImportQT.cpp

@@ -336,7 +336,7 @@ ProgressResult QTImportFileHandle::Import(TrackFactory *trackFactory,
                (sizeof(AudioBuffer) * numchan))) };
       abl->mNumberBuffers = numchan;
    
-      TrackHolders channels{ numchan };
+      NewChannelGroup channels{ numchan };
 
       const auto size = sizeof(float) * bufsize;
       ArraysOf<unsigned char> holders{ numchan, size };
@@ -395,11 +395,10 @@ ProgressResult QTImportFileHandle::Import(TrackFactory *trackFactory,
       res = (updateResult == ProgressResult::Success && err == noErr);
    
       if (res) {
-         for (const auto &channel: channels) {
+         for (auto &channel: channels)
             channel->Flush();
-         }
-   
-         outTracks.swap(channels);
+         if (!channels.empty())
+            outTracks.push_back(std::move(channels));
       }
 
       //

src/import/ImportRaw.cpp

@@ -107,7 +107,7 @@ void ImportRaw(wxWindow *parent, const wxString &fileName,
    sf_count_t offset = 0;
    double rate = 44100.0;
    double percent = 100.0;
-   TrackHolders channels;
+   TrackHolders results;
    auto updateResult = ProgressResult::Success;
 
    {
@@ -200,6 +200,8 @@ void ImportRaw(wxWindow *parent, const wxString &fileName,
           sf_subtype_more_than_16_bits(encoding))
          format = floatSample;
 
+      results.resize(1);
+      auto &channels = results[0];
       channels.resize(numChannels);
 
       auto iter = channels.begin();
@@ -295,9 +297,11 @@ void ImportRaw(wxWindow *parent, const wxString &fileName,
    if (updateResult == ProgressResult::Failed || updateResult == ProgressResult::Cancelled)
       throw UserException{};
 
-   for (const auto &channel : channels)
-      channel->Flush();
-   outTracks.swap(channels);
+   if (!results.empty() && !results[0].empty()) {
+      for (const auto &channel : results[0])
+         channel->Flush();
+      outTracks.swap(results);
+   }
 }
 
 //

src/import/ImportRaw.h

@@ -21,7 +21,10 @@ class wxWindow;
 
 #include <vector>
 
-using TrackHolders = std::vector<std::unique_ptr<WaveTrack>>;
+// Newly constructed WaveTracks that are not yet owned by a TrackList
+// are held in unique_ptr not shared_ptr
+using NewChannelGroup = std::vector< std::unique_ptr<WaveTrack> >;
+using TrackHolders = std::vector< NewChannelGroup >;
 
 
 void ImportRaw(wxWindow *parent, const wxString &fileName,

src/ondemand/ODDecodeFFmpegTask.cpp

@@ -109,17 +109,17 @@ private:
    int                  mStreamIndex;
 };
 
-auto ODDecodeFFmpegTask::FromList(const std::list<TrackHolders> &channels) -> Streams
+auto ODDecodeFFmpegTask::FromList( const TrackHolders &channels ) -> Streams
 {
    Streams streams;
    streams.reserve(channels.size());
    using namespace std;
    transform(channels.begin(), channels.end(), back_inserter(streams),
-      [](const TrackHolders &holders) {
+      [](const NewChannelGroup &holders) {
          Channels channels;
          channels.reserve(holders.size());
          transform(holders.begin(), holders.end(), back_inserter(channels),
-            mem_fn(&TrackHolders::value_type::get)
+            mem_fn(&NewChannelGroup::value_type::get)
          );
          return channels;
       }

src/ondemand/ODDecodeFFmpegTask.h

@@ -31,7 +31,8 @@ public:
    using Channels = std::vector < WaveTrack* >;
    using Streams = std::vector < Channels >;
 
-   static Streams FromList(const std::list<TrackHolders> &channels);
+   static Streams FromList(
+      const std::vector< std::vector< std::unique_ptr<WaveTrack> > > &channels);
 
    /// Constructs an ODTask
    ODDecodeFFmpegTask(const ScsPtr &scs, Streams &&channels, const std::shared_ptr<FFmpegContext> &context, int streamIndex);