From b63a63ceb2a43ef20e7ba79f173276d465575d14 Mon Sep 17 00:00:00 2001
From: Jonathan Thomas <jonathan@openshot.org>
Date: Mon, 17 Sep 2018 00:27:30 -0500
Subject: [PATCH] Fix many bugs around FPS and video length calculation
 (especially for MP3 and streaming WEBM formats). Also protecting
 samples_per_frame calculation to keep from crashing on undetected FPS.

---
 src/FFmpegReader.cpp | 33 ++++++++++++++++++++++++---------
 src/Frame.cpp        |  2 ++
 2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/src/FFmpegReader.cpp b/src/FFmpegReader.cpp
index 9711b2e5..243d7385 100644
--- a/src/FFmpegReader.cpp
+++ b/src/FFmpegReader.cpp
@@ -333,6 +333,11 @@ void FFmpegReader::UpdateAudioInfo()
 		info.height = 480;
 	}
 
+	// Fix invalid video lengths for certain types of files (MP3 for example)
+	if (info.has_video && ((info.duration * info.fps.ToDouble()) - info.video_length > 60)) {
+		info.video_length = info.duration * info.fps.ToDouble();
+	}
+
 	// Add audio metadata (if any found)
 	AVDictionaryEntry *tag = NULL;
 	while ((tag = av_dict_get(aStream->metadata, "", tag, AV_DICT_IGNORE_SUFFIX))) {
@@ -422,7 +427,7 @@ void FFmpegReader::UpdateVideoInfo()
 	}
 
 	// Override an invalid framerate
-	if (info.fps.ToFloat() > 240.0f || (info.fps.num == 0 || info.fps.den == 0)) {
+	if (info.fps.ToFloat() > 240.0f || (info.fps.num <= 0 || info.fps.den <= 0) || info.video_length <= 0) {
 		// Calculate FPS, duration, video bit rate, and video length manually
 		// by scanning through all the video stream packets
 		CheckFPS();
@@ -1864,7 +1869,6 @@ void FFmpegReader::CheckWorkingFrames(bool end_of_stream, int64_t requested_fram
 void FFmpegReader::CheckFPS()
 {
 	check_fps = true;
-	AV_ALLOCATE_IMAGE(pFrame, AV_GET_CODEC_PIXEL_FORMAT(pStream, pCodecCtx), info.width, info.height);
 
 	int first_second_counter = 0;
 	int second_second_counter = 0;
@@ -1872,6 +1876,7 @@ void FFmpegReader::CheckFPS()
 	int forth_second_counter = 0;
 	int fifth_second_counter = 0;
 	int frames_detected = 0;
+	int64_t pts = 0;
 
 	// Loop through the stream
 	while (true)
@@ -1891,7 +1896,7 @@ void FFmpegReader::CheckFPS()
 				UpdatePTSOffset(true);
 
 				// Get PTS of this packet
-				int64_t pts = GetVideoPTS();
+				pts = GetVideoPTS();
 
 				// Remove pFrame
 				RemoveAVFrame(pFrame);
@@ -1922,7 +1927,7 @@ void FFmpegReader::CheckFPS()
 
 	// Double check that all counters have greater than zero (or give up)
 	if (second_second_counter != 0 && third_second_counter != 0 && forth_second_counter != 0 && fifth_second_counter != 0) {
-		// Calculate average FPS
+		// Calculate average FPS (average of first few seconds)
 		int sum_fps = second_second_counter + third_second_counter + forth_second_counter + fifth_second_counter;
 		int avg_fps = round(sum_fps / 4.0f);
 
@@ -1931,22 +1936,32 @@ void FFmpegReader::CheckFPS()
 
 		// Update Duration and Length
 		info.video_length = frames_detected;
-		info.duration = frames_detected / round(sum_fps / 4.0f);
+		info.duration = frames_detected / (sum_fps / 4.0f);
+
+		// Update video bit rate
+		info.video_bit_rate = info.file_size / info.duration;
+	} else if (second_second_counter != 0 && third_second_counter != 0) {
+		// Calculate average FPS (only on second 2)
+		int sum_fps = second_second_counter;
+
+		// Update FPS
+		info.fps = Fraction(sum_fps, 1);
+
+		// Update Duration and Length
+		info.video_length = frames_detected;
+		info.duration = frames_detected / float(sum_fps);
 
 		// Update video bit rate
 		info.video_bit_rate = info.file_size / info.duration;
 	} else {
-
 		// Too short to determine framerate, just default FPS
 		// Set a few important default video settings (so audio can be divided into frames)
 		info.fps.num = 30;
 		info.fps.den = 1;
-		info.video_timebase.num = info.fps.den;
-		info.video_timebase.den = info.fps.num;
 
 		// Calculate number of frames
 		info.video_length = frames_detected;
-		info.duration = frames_detected / info.video_timebase.ToFloat();
+		info.duration = frames_detected / info.fps.ToFloat();
 	}
 }
 
diff --git a/src/Frame.cpp b/src/Frame.cpp
index 16a0d267..a00fc232 100644
--- a/src/Frame.cpp
+++ b/src/Frame.cpp
@@ -512,6 +512,8 @@ int Frame::GetSamplesPerFrame(int64_t number, Fraction fps, int sample_rate, int
 	// Subtract the previous frame's total samples with this frame's total samples.  Not all sample rates can
 	// be evenly divided into frames, so each frame can have have different # of samples.
 	int samples_per_frame = round(total_samples - previous_samples);
+	if (samples_per_frame < 0)
+		samples_per_frame = 0;
 	return samples_per_frame;
 }