Add function to get metadata from a file/track

README.md

@@ -48,10 +48,16 @@ ninja -C build install
 
 `bs.TrackInfo(string source[, bint enable_drefs = False, bint use_absolute_path = False])`
 
+`bs.Metadata(string source[, int track, bint enable_drefs = False, bint use_absolute_path = False])`
+
 `bs.SetDebugOutput(bint enable = False)`
 
 `bs.SetFFmpegLogLevel(int level = <quiet log level>)`
 
+The *TrackInfo* function only returns the most basic information about a track which is the type, codec and disposition. Its main use is to be able to implement custom track selection logic for the source functions.
+
+The *Metadata* function returns all the file or track metadata as key-value pairs depending on whether or not *track* is specified.
+
 ## Avisynth+ usage
 
 `BSAudioSource(string source[, int track = -1, int adjustdelay = -1, int threads = 0, bool enable_drefs = False, bool use_absolute_path = False, float drc_scale = 0, int cachemode = 1, string cachepath, int cachesize = 100])`

src/tracklist.cpp

@@ -107,7 +107,7 @@ std::map<std::string, std::string> BestTrackList::GetFileMetadata() const {
 }
 
 std::map<std::string, std::string> BestTrackList::GetTrackMetadata(int Track) const {
-    if (Track < 0 || Track >= FormatContext->nb_streams)
+    if (Track < 0 || Track >= static_cast<int>(FormatContext->nb_streams))
         throw BestSourceException("Invalid track number");
 
     std::map<std::string, std::string> Result;

src/vapoursynth.cpp

@@ -388,6 +388,35 @@ static void VS_CC GetTrackInfo(const VSMap *In, VSMap *Out, void *, VSCore *core
     }
 }
 
+static void VS_CC GetMetadata(const VSMap *In, VSMap *Out, void *, VSCore *core, const VSAPI *vsapi) {
+    BSInit();
+
+    int err;
+    std::filesystem::path Source = CreateProbablyUTF8Path(vsapi->mapGetData(In, "source", 0, nullptr));
+
+    int Track = vsapi->mapGetIntSaturated(In, "track", 0, &err);
+    if (err)
+        Track = -1;
+
+    std::map<std::string, std::string> Opts;
+    if (vsapi->mapGetInt(In, "enable_drefs", 0, &err))
+        Opts["enable_drefs"] = "1";
+    if (vsapi->mapGetInt(In, "use_absolute_path", 0, &err))
+        Opts["use_absolute_path"] = "1";
+
+    try {
+        std::unique_ptr<BestTrackList> TrackList(new BestTrackList(Source, &Opts));
+
+        auto Metadata = (Track < 0) ? TrackList->GetFileMetadata() : TrackList->GetTrackMetadata(Track);
+
+        for (const auto &Iter : Metadata) {
+            vsapi->mapSetData(Out, Iter.first.c_str(), Iter.second.c_str(), -1, dtUtf8, maAppend);
+        }
+    } catch (BestSourceException &e) {
+        vsapi->mapSetError(Out, (std::string("Metadata: ") + e.what()).c_str());
+    }
+}
+
 static void VS_CC SetDebugOutput(const VSMap *In, VSMap *, void *, VSCore *, const VSAPI *vsapi) {
     BSInit();
     SetBSDebugOutput(!!vsapi->mapGetInt(In, "enable", 0, nullptr));
@@ -407,6 +436,7 @@ VS_EXTERNAL_API(void) VapourSynthPluginInit2(VSPlugin *plugin, const VSPLUGINAPI
     vspapi->registerFunction("VideoSource", "source:data;track:int:opt;variableformat:int:opt;fpsnum:int:opt;fpsden:int:opt;rff:int:opt;threads:int:opt;seekpreroll:int:opt;enable_drefs:int:opt;use_absolute_path:int:opt;cachemode:int:opt;cachepath:data:opt;cachesize:int:opt;hwdevice:data:opt;extrahwframes:int:opt;timecodes:data:opt;start_number:int:opt;showprogress:int:opt;", "clip:vnode;", CreateBestVideoSource, nullptr, plugin);
     vspapi->registerFunction("AudioSource", "source:data;track:int:opt;adjustdelay:int:opt;threads:int:opt;enable_drefs:int:opt;use_absolute_path:int:opt;drc_scale:float:opt;cachemode:int:opt;cachepath:data:opt;cachesize:int:opt;showprogress:int:opt;", "clip:anode;", CreateBestAudioSource, nullptr, plugin);
     vspapi->registerFunction("TrackInfo", "source:data;enable_drefs:int:opt;use_absolute_path:int:opt;", "mediatype:int;mediatypestr:data;codec:int;codecstr:data;disposition:int;dispositionstr:data;", GetTrackInfo, nullptr, plugin);
+    vspapi->registerFunction("Metadata", "source:data;track:int:opt;enable_drefs:int:opt;use_absolute_path:int:opt;", "any", GetMetadata, nullptr, plugin);
     vspapi->registerFunction("SetDebugOutput", "enable:int;", "", SetDebugOutput, nullptr, plugin);
     vspapi->registerFunction("SetFFmpegLogLevel", "level:int;", "level:int;", SetLogLevel, nullptr, plugin);
 }