From 0853085ec629cdd819f8ad08dcd8b322be20642d Mon Sep 17 00:00:00 2001
From: Pierre Letessier <pierre.letessier@gmail.com>
Date: Sun, 26 Jan 2020 08:19:09 +0100
Subject: [PATCH] Merge pull request #16190 from
 pletessier:videocapture_skip_frames

Videocapture skip frames

* enable skipping frames

* update videoio_skip test
---
 modules/videoio/src/cap_ffmpeg_impl.hpp | 23 ++++++++++++
 modules/videoio/test/test_ffmpeg.cpp    | 48 +++++++++++++++++++++++++
 2 files changed, 71 insertions(+)

diff --git a/modules/videoio/src/cap_ffmpeg_impl.hpp b/modules/videoio/src/cap_ffmpeg_impl.hpp
index fdc6b31b19..c69cd74509 100644
--- a/modules/videoio/src/cap_ffmpeg_impl.hpp
+++ b/modules/videoio/src/cap_ffmpeg_impl.hpp
@@ -966,6 +966,29 @@ bool CvCapture_FFMPEG::open( const char* _filename )
         enc->thread_count = get_number_of_cpus();
 //#endif
 
+#if LIBAVCODEC_BUILD >= CALC_FFMPEG_VERSION(52, 123, 0)
+        AVDictionaryEntry* avdiscard_entry = av_dict_get(dict, "avdiscard", NULL, 0);
+
+        if (avdiscard_entry != 0) {
+            if(strcmp(avdiscard_entry->value, "all") == 0)
+                enc->skip_frame = AVDISCARD_ALL;
+            else if (strcmp(avdiscard_entry->value, "bidir") == 0)
+                enc->skip_frame = AVDISCARD_BIDIR;
+            else if (strcmp(avdiscard_entry->value, "default") == 0)
+                enc->skip_frame = AVDISCARD_DEFAULT;
+            else if (strcmp(avdiscard_entry->value, "none") == 0)
+                enc->skip_frame = AVDISCARD_NONE;
+#if LIBAVCODEC_BUILD >= CALC_FFMPEG_VERSION(54, 59, 100)
+            else if (strcmp(avdiscard_entry->value, "nonintra") == 0)
+                enc->skip_frame = AVDISCARD_NONINTRA;
+#endif
+            else if (strcmp(avdiscard_entry->value, "nonkey") == 0)
+                enc->skip_frame = AVDISCARD_NONKEY;
+            else if (strcmp(avdiscard_entry->value, "nonref") == 0)
+                enc->skip_frame = AVDISCARD_NONREF;
+        }
+#endif
+
 #if LIBAVFORMAT_BUILD < CALC_FFMPEG_VERSION(53, 2, 0)
 #define AVMEDIA_TYPE_VIDEO CODEC_TYPE_VIDEO
 #endif
diff --git a/modules/videoio/test/test_ffmpeg.cpp b/modules/videoio/test/test_ffmpeg.cpp
index 6519c57751..10f41daf7a 100644
--- a/modules/videoio/test/test_ffmpeg.cpp
+++ b/modules/videoio/test/test_ffmpeg.cpp
@@ -303,6 +303,54 @@ const videoio_container_params_t videoio_container_params[] =
 
 INSTANTIATE_TEST_CASE_P(/**/, videoio_container, testing::ValuesIn(videoio_container_params));
 
+typedef tuple<string, string, int> videoio_skip_params_t;
+typedef testing::TestWithParam< videoio_skip_params_t > videoio_skip;
+
+TEST_P(videoio_skip, DISABLED_read)  // optional test, may fail in some configurations
+{
+#if CV_VERSION_MAJOR >= 4
+    if (!videoio_registry::hasBackend(CAP_FFMPEG))
+        throw SkipTestException("Backend was not found");
+#endif
+
+    const string path = get<0>(GetParam());
+    const string env = get<1>(GetParam());
+    const int expectedFrameNumber = get<2>(GetParam());
+
+    #ifdef _WIN32
+        _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", env.c_str());
+    #else
+        setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", env.c_str(), 1);
+    #endif
+    VideoCapture container(findDataFile(path), CAP_FFMPEG);
+    #ifdef _WIN32
+        _putenv_s("OPENCV_FFMPEG_CAPTURE_OPTIONS", "");
+    #else
+        setenv("OPENCV_FFMPEG_CAPTURE_OPTIONS", "", 1);
+    #endif
+
+    ASSERT_TRUE(container.isOpened());
+
+    Mat reference;
+    int nframes = 0, n_err = 0;
+    while (container.isOpened())
+    {
+        if (container.read(reference))
+            nframes++;
+        else if (++n_err > 3)
+            break;
+    }
+    EXPECT_EQ(expectedFrameNumber, nframes);
+}
+
+const videoio_skip_params_t videoio_skip_params[] =
+{
+    videoio_skip_params_t("video/big_buck_bunny.mp4", "", 125),
+    videoio_skip_params_t("video/big_buck_bunny.mp4", "avdiscard;nonkey", 11)
+};
+
+INSTANTIATE_TEST_CASE_P(/**/, videoio_skip, testing::ValuesIn(videoio_skip_params));
+
 //==========================================================================
 
 //////////////////////////////// Parallel VideoWriters and VideoCaptures ////////////////////////////////////