1，导出时使用背景音乐

BFRecordScreenKit/Classes/BFRecordExport.swift

@@ -43,6 +43,9 @@ public class BFRecordExport {
         }
     }
 
+    //选择的背景音乐信息
+    public var bgmModel:PQVoiceModel?
+    
     var count = 0
 
     var stickerRanges = [CMTimeRange]()
@@ -563,7 +566,16 @@ extension BFRecordExport {
                 tempParameters += mergeRecordVoiceOnly(voices: voices, composition)
             }
         }
+        //add by ak  处理背景音乐 如果选择了背景音乐添加背景音乐音轨
+        BFLog(message: "合成视频总时长:\(composition.duration.seconds)")
+        if bgmModel != nil, bgmModel?.wavFilePath != nil {
+            let bgmParameters = PQPlayerViewModel.dealWithBGMTrack(bgmData: bgmModel!, totalDuration: composition.duration.seconds, composition: composition)
+            if bgmParameters.count > 0 {
+                tempParameters += bgmParameters
+            }
+        }
         audioMix.inputParameters = tempParameters
+        
         return (audioMix, composition)
     }
 
@@ -593,6 +605,7 @@ extension BFRecordExport {
                 continue
             }
             tempParameters += PQPlayerViewModel.dealWithMaterialTrack(stickerModel: model, composition: composition)
+            totalDur += model.aptDuration
         }
 
         return tempParameters