public AutoMixingResult AutoMix(AutoMixingContext context)
{
if (context == null) throw new ArgumentNullException("context");
IEnumerable<IMixItem> unknownTracks = context.TracksToMix.Where(c => c.IsUnknownKeyOrBpm).ToList();
IEnumerable<IMixItem> mixableTracks = context.TracksToMix.Except(unknownTracks);
AutoMixingBucket optionalStartVertex;
AdjacencyGraph<AutoMixingBucket, AutoMixEdge> graph
= BuildGraph(mixableTracks, unknownTracks, context, out optionalStartVertex);
AddPreferredEdges(graph);
IEnumerable<AutoMixingBucket> mixedBuckets = GetPreferredMix(graph,
optionalStartVertex, context.GetOptionalEndKey(), computeAll: false);
if (mixedBuckets == null)
{
AddFallbackEdges(graph);
mixedBuckets = GetPreferredMix(graph, optionalStartVertex,
context.GetOptionalEndKey(),
computeAll: true);
}
if (mixedBuckets == null)
{
Log.Debug("Failed to find any auto mix paths. Returning unmodified tracks.");
return AutoMixingResult.Failure(context);
}
IEnumerable<IMixItem> mixedTracks = UnpackBuckets(mixedBuckets);
return AutoMixingResult.Success(context, mixedTracks, unknownTracks);
}
static AdjacencyGraph<AutoMixingBucket, AutoMixEdge> BuildGraph(
IEnumerable<IMixItem> mixableTracks,
IEnumerable<IMixItem> unknownTracks,
AutoMixingContext context, out AutoMixingBucket optionalStartVertex)
{
IList<AutoMixingBucket> buckets = mixableTracks
.GroupBy(g => g.ActualKey)
.Select(g => new AutoMixingBucket(g, g.Key))
.ToList();
Log.DebugFormat("{0} mixable tracks ({1} buckets aka vertices), {2} unmixable tracks (unknown key/BPM).",
mixableTracks.Count(), buckets.Count(), unknownTracks.Count());
var graph = new AdjacencyGraph<AutoMixingBucket, AutoMixEdge>();
graph.AddVertexRange(buckets);
// If we are auto-mixing a subset of tracks within a mix, we must
// keep them harmonically compatible with the tracks immediately
// before and after i.e. (preceeding)(tracks to mix)(following).
//
// To find such a path, we unfortunately can't just look for paths
// where (start = preceeding and end = following) because they
// might be using different keys that are not used by any of the
// tracks in the graph.
//
// To get around this problem, we add empty 'placeholder' buckets
// (vertices) to the graph for the preceeding/following keys, and
// look for paths that use these vertices as start/end points.
// This works because when we unpack the buckets, these vertices
// simply unpack as empty (they don't contain any tracks) so we can
// use them for the final path of mix items without producing any
// messy placeholder/temporary tracks.
optionalStartVertex = AddPlaceholderVertexIfRequired(graph, context.GetOptionalStartKey());
AddPlaceholderVertexIfRequired(graph, context.GetOptionalEndKey());
return graph;
}