Newest 'ffmpeg' Questions - Stack Overflow
Les articles publiés sur le site
-
Difference behaviour between Ubuntu and Windows for popen, _popen
30 avril, par Humam HelfawiI need to open FFMPEG pipe and write frames data to that pipe. I am using this code:
#ifdef _WIN32 #define POPEN _popen #define PCLOSE _pclose #else #define POPEN popen #define PCLOSE pclose #endif // FFmpeg command to receive raw BGR24 data and encode with libx264 std::ostringstream oss; oss << "ffmpeg -y -f rawvideo -pixel_format bgr24 " << "-video_size " << width << "x" << height << " " << "-framerate " << fps << " -i - " << "-c:v libx264 -preset ultrafast " << "" << video_path << ""; std::string cmd = oss.str(); #ifdef _WIN32 auto mode = "wb"; #else auto mode = "w"; #endif pipe_ = POPEN(cmd.c_str(), mode); if (!pipe_) { throw std::runtime_error("[FFmpegWriter::FFmpegWriter] FFmpeg pipe could not be oppnened"); }The writing (in loop) looks like:
size_t written = fwrite(img.data, 1, img.total() * img.elemSize(), pipe_);This works fine but it is much slower on Ubuntu (while writing frames) than it is on Windows. The
wboption does not work on ubuntu and return empty pipe_. What exactly the problem here:- Why
wbdoes not work on Ubuntu? - if
wis the way to go on Ubuntu, why it is much slower than windows (2-3X)?
- Why
-
FFmpeg webcam image capture from default Windows webcam
29 avril, par Mark RyanI want to capture a webcam image from my default Windows webcam without specifying the webcam name and save it as a JPG. I also want to scale and crop it to 640x480. I have come up with -
ffmpeg -f dshow -i "video=EasyCamera" -vf scale=-1:480,crop=640:480 -frames:v 1 test.jpg -y
And it works fine, but I want to be able to be able to capture the image without having to specify the camera name. Is this possible?
I have been able to do it with the following -
ffmpeg.exe -f vfwcap -i 0 -vf scale=-1:480,crop=640:480 -frames:v 1 test.jpg -y
But vfwcap is very old & I shouldn't be using it.
Sorry if this is a very basic question but I am new to FFmpeg and have spent a long time try to figure this out. Any help would be greatly appreciated
-
Can't set seeker in GSTREAMER cv2, python
29 avril, par Alperen ÖlçerI want to skip n seconds forward and backward in gstreamer cv2 capture for recorded videos. But when I use
cap_gstreamer.set(cv2.CAP_PROP_POS_FRAMES, fps*skip_second)it resets seeker to beginning of video. How can I solve it? I wrote an example, used recorded clock video.import cv2 video_p = '/home/alperenlcr/Videos/clock.mp4' cap_gstreamer = cv2.VideoCapture(video_p, cv2.CAP_GSTREAMER) cap_ffmpeg = cv2.VideoCapture(video_p, cv2.CAP_FFMPEG) fps = cap_gstreamer.get(cv2.CAP_PROP_FPS) skip_second = 100 im1 = cv2.resize(cap_gstreamer.read()[1], (960, 540)) im1_ffmpeg = cv2.resize(cap_ffmpeg.read()[1], (960, 540)) cap_gstreamer.set(cv2.CAP_PROP_POS_FRAMES, fps*skip_second) cap_ffmpeg.set(cv2.CAP_PROP_POS_FRAMES, fps*skip_second) im2 = cv2.resize(cap_gstreamer.read()[1], (960, 540)) im2_ffmpeg = cv2.resize(cap_ffmpeg.read()[1], (960, 540)) merge_gstreamer = cv2.hconcat([im1, im2]) merge_ffmpeg = cv2.hconcat([im1_ffmpeg, im2_ffmpeg]) cv2.imshow(str(skip_second) + ' gstreamer', merge_gstreamer) cv2.imshow(str(skip_second) + ' ffmpeg', merge_ffmpeg) cv2.waitKey(0) cv2.destroyAllWindows() cap_gstreamer.release() cap_ffmpeg.release()Result:
My cv2 build is like:
>>> print(cv2.getBuildInformation()) General configuration for OpenCV 4.8.1 ===================================== Version control: 4.8.1-dirty Extra modules: Location (extra): /home/alperenlcr/SourceInstalls/opencv_contrib/modules Version control (extra): 4.8.1 Platform: Timestamp: 2024-12-02T13:44:58Z Host: Linux 6.8.0-49-generic x86_64 CMake: 3.22.1 CMake generator: Unix Makefiles CMake build tool: /usr/bin/gmake Configuration: RELEASE CPU/HW features: Baseline: SSE SSE2 SSE3 requested: SSE3 Dispatched code generation: SSE4_1 SSE4_2 FP16 AVX AVX2 AVX512_SKX requested: SSE4_1 SSE4_2 AVX FP16 AVX2 AVX512_SKX SSE4_1 (18 files): + SSSE3 SSE4_1 SSE4_2 (2 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 (1 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 AVX AVX (8 files): + SSSE3 SSE4_1 POPCNT SSE4_2 AVX AVX2 (37 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX512_SKX (8 files): + SSSE3 SSE4_1 POPCNT SSE4_2 FP16 FMA3 AVX AVX2 AVX_512F AVX512_COMMON AVX512_SKX C/C++: Built as dynamic libs?: NO C++ standard: 11 C++ Compiler: /usr/bin/c++ (ver 10.5.0) C++ flags (Release): -fsigned-char -ffast-math -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -O3 -DNDEBUG -DNDEBUG C++ flags (Debug): -fsigned-char -ffast-math -W -Wall -Wreturn-type -Wnon-virtual-dtor -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow -Wsign-promo -Wuninitialized -Wsuggest-override -Wno-delete-non-virtual-dtor -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -fvisibility-inlines-hidden -g -O0 -DDEBUG -D_DEBUG C Compiler: /usr/bin/cc C flags (Release): -fsigned-char -ffast-math -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -O3 -DNDEBUG -DNDEBUG C flags (Debug): -fsigned-char -ffast-math -W -Wall -Wreturn-type -Waddress -Wsequence-point -Wformat -Wformat-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wshadow -Wuninitialized -Wno-comment -Wimplicit-fallthrough=3 -Wno-strict-overflow -fdiagnostics-show-option -Wno-long-long -pthread -fomit-frame-pointer -ffunction-sections -fdata-sections -msse -msse2 -msse3 -fvisibility=hidden -g -O0 -DDEBUG -D_DEBUG Linker flags (Release): -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined Linker flags (Debug): -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a -Wl,--gc-sections -Wl,--as-needed -Wl,--no-undefined ccache: NO Precompiled headers: NO Extra dependencies: /usr/lib/x86_64-linux-gnu/libjpeg.so /usr/lib/x86_64-linux-gnu/libpng.so /usr/lib/x86_64-linux-gnu/libtiff.so /usr/lib/x86_64-linux-gnu/libz.so /usr/lib/x86_64-linux-gnu/libfreetype.so /usr/lib/x86_64-linux-gnu/libharfbuzz.so Iconv::Iconv m pthread cudart_static dl rt nppc nppial nppicc nppidei nppif nppig nppim nppist nppisu nppitc npps cublas cudnn cufft -L/usr/lib/x86_64-linux-gnu -L/usr/lib/cuda/lib64 3rdparty dependencies: libprotobuf ade ittnotify libwebp libopenjp2 IlmImf quirc ippiw ippicv OpenCV modules: To be built: aruco bgsegm bioinspired calib3d ccalib core cudaarithm cudabgsegm cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev datasets dnn dnn_objdetect dnn_superres dpm face features2d flann freetype fuzzy gapi hfs highgui img_hash imgcodecs imgproc intensity_transform line_descriptor mcc ml objdetect optflow phase_unwrapping photo plot python3 quality rapid reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab wechat_qrcode xfeatures2d ximgproc xobjdetect xphoto Disabled: cudacodec world Disabled by dependency: - Unavailable: alphamat cvv hdf java julia matlab ovis python2 sfm viz Applications: tests perf_tests examples apps Documentation: NO Non-free algorithms: NO GUI: GTK2 QT: NO GTK+: YES (ver 2.24.33) GThread : YES (ver 2.72.4) GtkGlExt: NO OpenGL support: NO VTK support: NO Media I/O: ZLib: /usr/lib/x86_64-linux-gnu/libz.so (ver 1.2.11) JPEG: /usr/lib/x86_64-linux-gnu/libjpeg.so (ver 80) WEBP: build (ver encoder: 0x020f) PNG: /usr/lib/x86_64-linux-gnu/libpng.so (ver 1.6.37) TIFF: /usr/lib/x86_64-linux-gnu/libtiff.so (ver 42 / 4.3.0) JPEG 2000: build (ver 2.5.0) OpenEXR: build (ver 2.3.0) HDR: YES SUNRASTER: YES PXM: YES PFM: YES Video I/O: DC1394: NO FFMPEG: YES avcodec: YES (58.134.100) avformat: YES (58.76.100) avutil: YES (56.70.100) swscale: YES (5.9.100) swresample: YES (3.9.100) GStreamer: YES (1.20.3) v4l/v4l2: YES (linux/videodev2.h) Parallel framework: TBB (ver 2021.5 interface 12050) Trace: YES (with Intel ITT) Other third-party libraries: Intel IPP: 2021.8 [2021.8.0] at: /home/alperenlcr/SourceInstalls/opencv/build/3rdparty/ippicv/ippicv_lnx/icv Intel IPP IW: sources (2021.8.0) at: /home/alperenlcr/SourceInstalls/opencv/build/3rdparty/ippicv/ippicv_lnx/iw VA: NO Lapack: NO Eigen: NO Custom HAL: NO Protobuf: build (3.19.1) Flatbuffers: builtin/3rdparty (23.5.9) NVIDIA CUDA: YES (ver 11.5, CUFFT CUBLAS NVCUVID NVCUVENC FAST_MATH) NVIDIA GPU arch: 86 NVIDIA PTX archs: cuDNN: YES (ver 8.6.0) OpenCL: YES (no extra features) Include path: /home/alperenlcr/SourceInstalls/opencv/3rdparty/include/opencl/1.2 Link libraries: Dynamic load ONNX: NO Python 3: Interpreter: /usr/bin/python3 (ver 3.10.12) Libraries: /usr/lib/x86_64-linux-gnu/libpython3.10.so (ver 3.10.12) numpy: /usr/lib/python3/dist-packages/numpy/core/include (ver 1.21.5) install path: lib/python3.10/dist-packages/cv2/python-3.10 Python (for build): /usr/bin/python3 Java: ant: NO Java: NO JNI: NO Java wrappers: NO Java tests: NO Install to: /usr/local ----------------------------------------------------------------- -
How to add dynamic captions with animations on a video in a cross-platform Android & iOS app and export it as a final video ? [closed]
29 avril, par Danial QskI'm building a cross-platform mobile app using Flutter (or React Native) where users can:
Add dynamic text captions with animations over a video, similar to TikTok
See these changes in real-time during video playback
Export the video with the animated captions burned into the output (e.g., MP4)
What I’ve implemented so far:
Video playback using video_player in Flutter (or react-native-video).
Captions are rendered using Canvas/UI layer during playback.
Problem: While I can overlay animated text in the UI, I can't figure out how to include these in the exported video. I’m considering using FFmpeg to burn in the captions, but I’m unclear how to integrate it with the animated UI overlays or render them into a final video on both Android and iOS.
What I want to achieve:
Efficient way to render animated text overlays onto a video and export it as a final video file on both Android and iOS.
Maintain good performance for real-time playback and smooth export.
What approaches or processing pipelines could achieve this? (For example, rendering the UI layer to an offscreen video, integrating with FFmpeg, or using native rendering techniques.)
-
ffmpeg : Stream specifiers per format/codec [closed]
29 avril, par nathan wurtzI was wondering if it were possible to select all the stream in a specific format.
Example :
Stream #0:0(eng): Video: h264 (High), yuv420p(tv, smpte170m/smpte170m/bt709, progressive), 710x480 [SAR 32:27 DAR 142:81], SAR 841:710 DAR 841:480, 29.97 fps, 29.97 tbr, 1k tbn, 180k tbc (default) Stream #0:1(deu): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s (default) Stream #0:2(deu): Subtitle: dvd_subtitle, 720x480 Stream #0:3(eng): Subtitle: dvd_subtitle, 720x480 Stream #0:4(fra): Subtitle: dvd_subtitle, 720x480 Stream #0:5(spa): Subtitle: dvd_subtitle, 720x480 Stream #0:6(eng): Subtitle: subrip (default)I would like to select all the dvd_subtitle to set the 'codec' to copy. And select the subrip subtitle to set the 'codec' to mov_text. And all that without having to specify the stream number (I would like to reuse the same arguments to convert other videos)
I thought about doing something like that :
-c:m:dvd_subtitle copy -c:m:subrip mov_text, but that obviously didn't work.I have read the doc https://ffmpeg.org/ffmpeg.html#Stream-specifiers but didn't find a solution.
Thank you for reading
