Subsonic API: try to not transcode if the requested format/max bitrate is compatible with the actual file

src/libs/subsonic/impl/entrypoints/MediaRetrieval.cpp

@@ -19,6 +19,7 @@
 
 #include "MediaRetrieval.hpp"
 
+#include "av/IAudioFile.hpp"
 #include "av/TranscodeParameters.hpp"
 #include "av/TranscodeResourceHandlerCreator.hpp"
 #include "av/Types.hpp"
@@ -99,8 +100,23 @@ namespace API::Subsonic
                 parameters.inputFileParameters.duration = track->getDuration();
             }
 
-            if (format != "raw") // raw => no transcode
+            if (format == "raw") // raw => no transcode
+                return parameters;
+
+            const auto audioFile{ Av::parseAudioFile(parameters.inputFileParameters.trackPath) };
+
+            // check if transcode is really needed or not
+            // same format as requested, bitrate is lower than requested => no need to transcode
+            if (const auto streamInfo{ audioFile->getBestStreamInfo() })
             {
+                // assume reported codec is "mp3", "opus", "vorbis", etc.
+                if (StringUtils::stringCaseInsensitiveEqual(streamInfo->codec, format) && (maxBitRate == 0 || (streamInfo->bitrate / 1000) <= maxBitRate))
+                {
+                    LMS_LOG(API_SUBSONIC, DEBUG) << "stream parameters are compatible with actual file: no transcode";
+                    return parameters;
+                }
+            }
+
             const User::pointer user{ User::find(context.dbSession, context.userId) };
             if (!user)
                 throw UserNotAuthorizedError{};
@@ -117,8 +133,7 @@ namespace API::Subsonic
 
             transcodeParameters.bitrate = user->getSubsonicDefaultTranscodeBitrate();
             if (maxBitRate != 0)
-                    transcodeParameters.bitrate = Utils::clamp(transcodeParameters.bitrate, std::size_t{ 48 }, maxBitRate);
+                transcodeParameters.bitrate = Utils::clamp(transcodeParameters.bitrate, std::size_t{ 48000 }, maxBitRate * 1000);
-            }
 
             return parameters;
         }