added option to allow potentially unsafe seeking with the ffmpeg video provider. named "ffmpeg allow unsafe seeking" and defaults to false.

Originally committed to SVN as r2254.

aegisub/options.cpp

@@ -165,6 +165,7 @@ void OptionsManager::LoadDefaults(bool onlyDefaults,bool doOverride) {
 	#else
 	SetText(_T("Video Provider"),_T("FFMPEG"),1945);
 	#endif
+	SetBool(_T("FFmpeg allow unsafe seeking"),false);
 	SetBool(_T("Allow Ancient Avisynth"),false,1700);
 	SetText(_T("Avisynth subs renderer"),_T("vsfilter"),1700);
 	SetBool(_T("Avisynth render own subs"),true,1700);

aegisub/video_provider_lavc.cpp

@@ -57,6 +57,7 @@
 #include "ass_file.h"
 #include "lavc_keyframes.h"
 #include "video_context.h"
+#include "options.h"
 
 
 ///////////////
@@ -154,6 +155,8 @@ void LAVCVideoProvider::LoadVideo(Aegisub::String filename, double fps) {
 		// Set frame
 		frameNumber = -1;
 		lastFrameNumber = -1;
+
+		allowUnsafeSeeking = Options.AsBool(_T("FFmpeg allow unsafe seeking"));
 	}
 
 	// Catch errors
@@ -398,9 +401,13 @@ const AegiVideoFrame LAVCVideoProvider::GetFrame(int n,int formatType) {
 					hasSeeked = false;
 
 					// is the seek destination known? does it belong to a frame?
-					if (startTime < 0 || (frameNumber = FrameFromDTS(startTime)) < 0)
-						throw _T("ffmpeg video provider: frame accurate seeking failed");
-						//frameNumber = ClosestFrameFromDTS(startTime);
+					if (startTime < 0 || (frameNumber = FrameFromDTS(startTime)) < 0) {
+						if (allowUnsafeSeeking)
+							frameNumber = ClosestFrameFromDTS(startTime);
+						else
+							throw _T("ffmpeg video provider: frame accurate seeking failed");
+					}
+						
 				}
 
 				frameNumber++;

aegisub/video_provider_lavc.h

@@ -82,6 +82,7 @@ private:
 
 	wxArrayInt bytePos;
 
+	bool allowUnsafeSeeking;
 	bool isMkv;
 	int64_t lastDecodeTime;
 	int frameNumber;