potok/opencv
1
0
Fork 0
mirror of https://github.com/opencv/opencv.git synced 2026-07-21 19:33:03 +04:00
Code Packages Releases Wiki Activity

Merge pull request #27523 from inventshah:fix-set-then-get-pos

Browse Source 
FIX: CvCapture_FFMPEG::setProperty(CAP_PROP_POS_*) followed by getProperty #27523

Partially fixes #23088 and #23472. This PR fixes `get(CAP_PROP_POS_MSEC)` calls after a `set(CAP_PROP_POS_*)` without calling `read` first.

Since `seek` calls `grabFrame` which already sets `picture_pts`, manually setting `picture_pts` anywhere else in the call stack should not be necessary (except for the special case of seeking to frame 0).

Minimal example from #23088
```cpp
for(int i = 0; i < 3; i++) cap.read(img);
printf("at: %f frames, %f msec\n", cap.get(CAP_PROP_POS_FRAMES), cap.get(CAP_PROP_POS_MSEC));

cap.set(CAP_PROP_POS_FRAMES, 3);
printf("at: %f frames, %f msec\n", cap.get(CAP_PROP_POS_FRAMES), cap.get(CAP_PROP_POS_MSEC));
```

Current
```txt
at: 3.000000 frames, 80.000000 msec
at: 3.000000 frames, 0.234375 msec
```

PR
```txt
at: 3.000000 frames, 80.000000 msec
at: 3.000000 frames, 80.000000 msec
```

It similarly helps with `CAP_PROP_POS_MSEC`:

Current
```txt
at: 3.000000 frames, 80.000000 msec
at: 2.000000 frames, 6.250000 msec
```

PR
```txt
at: 3.000000 frames, 80.000000 msec
at: 2.000000 frames, 40.000000 msec
```

Note the seek operation is still inconsistent between the `CAP_PROP_POS_*` options as mentioned by #23088, and VFR video seeking has issues discussed in #9053. For fixed-frame rate video, we could change 0.5 to 1 in `void CvCapture_FFMPEG::seek(double sec);` to align `CAP_PROP_POS_MSEC` with `CAP_PROP_POS_FRAMES`, but `CAP_POS_AVI_RATIO` and VFR video would still be broken.

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake
This commit is contained in:
Sachin Shah
2025-07-14 04:59:44 -04:00
committed by GitHub
parent 0a1a07d62e
commit 4c024c35fb
2 changed files with 34 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files
modules/videoio/test/test_ffmpeg.cpp
+27
View File
@@ -1030,4 +1030,31 @@ inline static std::string videoio_ffmpeg_mismatch_name_printer(const testing::Te
INSTANTIATE_TEST_CASE_P(/**/, videoio_ffmpeg_channel_mismatch, testing::ValuesIn(mismatch_cases), videoio_ffmpeg_mismatch_name_printer);
// PR: https://github.com/opencv/opencv/pull/27523
// TODO: Enable the tests back on Windows after FFmpeg plugin rebuild
#ifndef _WIN32
// related issue: https://github.com/opencv/opencv/issues/23088
TEST(ffmpeg_cap_properties, set_pos_get_msec)
{
if (!videoio_registry::hasBackend(CAP_FFMPEG))
throw SkipTestException("FFmpeg backend was not found");
string video_file = findDataFile("video/big_buck_bunny.mp4");
VideoCapture cap;
EXPECT_NO_THROW(cap.open(video_file, CAP_FFMPEG));
ASSERT_TRUE(cap.isOpened()) << "Can't open the video";
cap.set(CAP_PROP_POS_FRAMES, 25);
EXPECT_EQ(cap.get(CAP_PROP_POS_MSEC), 1000.0);
cap.set(CAP_PROP_POS_MSEC, 525);
EXPECT_EQ(cap.get(CAP_PROP_POS_MSEC), 500.0);
cap.set(CAP_PROP_POS_AVI_RATIO, 0);
EXPECT_EQ(cap.get(CAP_PROP_POS_MSEC), 0.0);
}
#endif // WIN32
}} // namespace