From 9de164cfba8ac6384f7c87e5dab4d20a0bd26dfe Mon Sep 17 00:00:00 2001
From: itsmattkc <itsmattkc@gmail.com>
Date: Fri, 14 Feb 2020 10:05:10 +1100
Subject: [PATCH] ffmpeg: disable multithreading in favor of our own

Our renderer system is already heavily multithreaded and prioritized to keep the
main thread active. As a result, FFmpeg receives little benefits from being
multithreaded and is actually detrimental to our main thread as it hasn't been
prioritized to keep the main thread as active as possible.
---
 app/codec/ffmpeg/ffmpegdecoder.cpp | 12 +++++++++---
 app/codec/ffmpeg/ffmpegdecoder.h   |  4 ++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/app/codec/ffmpeg/ffmpegdecoder.cpp b/app/codec/ffmpeg/ffmpegdecoder.cpp
index 3e0398c6f..f5cd7e2f7 100644
--- a/app/codec/ffmpeg/ffmpegdecoder.cpp
+++ b/app/codec/ffmpeg/ffmpegdecoder.cpp
@@ -47,7 +47,8 @@ FFmpegDecoder::FFmpegDecoder() :
   scale_ctx_(nullptr),
   pkt_(nullptr),
   frame_(nullptr),
-  opts_(nullptr)
+  opts_(nullptr),
+  multithreading_(false)
 {
 }
 
@@ -125,8 +126,8 @@ bool FFmpegDecoder::Open()
     return false;
   }
 
-  // enable multithreading on decoding
-  error_code = av_dict_set(&opts_, "threads", "auto", 0);
+  // Set multithreading setting
+  error_code = av_dict_set(&opts_, "threads", multithreading_ ? "auto" : "1", 0);
 
   // Handle failure to set multithreaded decoding
   if (error_code < 0) {
@@ -524,6 +525,11 @@ bool FFmpegDecoder::SupportsAudio()
   return true;
 }
 
+void FFmpegDecoder::SetMultithreading(bool e)
+{
+  multithreading_ = e;
+}
+
 void FFmpegDecoder::ConformInternal(SwrContext* resampler, WaveOutput* output, const char* in_data, int in_sample_count)
 {
   // Determine how many samples the output will be
diff --git a/app/codec/ffmpeg/ffmpegdecoder.h b/app/codec/ffmpeg/ffmpegdecoder.h
index 2d80ffbaf..e88010957 100644
--- a/app/codec/ffmpeg/ffmpegdecoder.h
+++ b/app/codec/ffmpeg/ffmpegdecoder.h
@@ -61,6 +61,8 @@ public:
   virtual bool SupportsVideo() override;
   virtual bool SupportsAudio() override;
 
+  void SetMultithreading(bool e);
+
 private:
   void ConformInternal(SwrContext *resampler, WaveOutput *output, const char *in_data, int in_sample_count);
 
@@ -145,6 +147,8 @@ private:
 
   QVector<int64_t> frame_index_;
 
+  bool multithreading_;
+
 };
 
 #endif // FFMPEGDECODER_H