From ec24944a03d696c70047254a0be8cc2387668452 Mon Sep 17 00:00:00 2001
From: romanmeta <romanmal@meta.com>
Date: Tue, 10 Sep 2024 15:12:01 -0700
Subject: [PATCH] Pass thread count to ffmpeg's filtergraph (#209)

---
 src/torchcodec/decoders/_core/VideoDecoder.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/torchcodec/decoders/_core/VideoDecoder.cpp b/src/torchcodec/decoders/_core/VideoDecoder.cpp
index 5aaffbd1..2dceaff4 100644
--- a/src/torchcodec/decoders/_core/VideoDecoder.cpp
+++ b/src/torchcodec/decoders/_core/VideoDecoder.cpp
@@ -254,6 +254,9 @@ void VideoDecoder::initializeFilterGraphForStream(
   }
   filterState.filterGraph.reset(avfilter_graph_alloc());
   TORCH_CHECK(filterState.filterGraph.get() != nullptr);
+  if (options.ffmpegThreadCount.has_value()) {
+    filterState.filterGraph->nb_threads = options.ffmpegThreadCount.value();
+  }
   const AVFilter* buffersrc = avfilter_get_by_name("buffer");
   const AVFilter* buffersink = avfilter_get_by_name("buffersink");
   enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_RGB24, AV_PIX_FMT_NONE};