3 articles

6 juillet

Newest 'ffmpeg' Questions - Stack Overflow http://stackoverflow.com/questions/tagged/ffmpeg

16:21
Is there a way to force FFMPEG to decode a video stream with alpha from a WebM video encoded with libvpx-vp9? - David Newest 'ffmpeg' Questions - Stack Overflow

I have a WebM file with one video stream that was encoded with VP9 (libvpx-vp9). I wrote a C++ program to extract the frames from the video stream and save them out as PNG's. This works fine except that the resulting PNG's are missing alpha. If I extract the frames from the same WebM file using FFMPEG the resulting PNG's do contain alpha. Here is the output from FFMPEG: $ ffmpeg -c:v libvpx-vp9 -i temp/anim.webm temp/output-%3d.png [libvpx-vp9 ⓐ 0000024732b106c0] v1.10.0-rc1-11-gcb0d8ce31 Last message repeated 1 times Input #0, (...)
13:01
What codec in OpenCV can do a stronger compression than default 'mp4v'? - ullix Newest 'ffmpeg' Questions - Stack Overflow

My project does video recording from a microscope camera, and one experiment can run for days and even weeks. This takes plenty of filespace, so I want as strong a compression as possible. Quality is not a major concern. Currently I use the default 'mp4v' codec with opencv on Python. It works. I tried all codecs Google could find, and surprisingly, only very few worked. And those few that did work were even worse in compression. Where is the limitation? Is it Opencv (4.11.0.86)? Is it FFMPEG (7.1.1)? Is it the distribution (Ubuntu Mate 25.04)? Is it the CPU (AMD (...)

22:14
Randomly extract video frames from multiple files [closed] - PatraoPedro Newest 'ffmpeg' Questions - Stack Overflow

I have a folder with hundreds of video files (*.avi), each one with more or less an hour long. What I would like to achieve is a piece of code that could go through each one of those videos and randomly select two or three frames from each file and then stitch it back together or alternatively save the frames in a folder as jpegs. Initially I thought I could do this using R but quickly I've realised that I would need something else possibly working together with R. Is it possible to call FFMPEG from R to do the task (...)