Hi, I've used ffmpeg to encode several PNG images to a raw YUV video stream as described in the documentation: ffmpeg -f image2 -i %03d.png rawvideo.yuv I encoded 32 images with a resolution of 640x360 pixels that way. However, when I want to compress the raw YUV video with x264 to an MPEG-4 video stream, x264 claims that the file contains 64 images: x264 --progress -o video.264 rawvideo.yuv 640x360 [SNIP] encoded 64 frames, 7.52 fps, 13388.87 kb/s A comparison of the file sizes of the PNG images and the YUV file revealed that the YUV file is approx 2-3 times bigger than the PNG images together. I'd appreciate if somebody could explain to my why the two tools detect a different number of frames. Is ffmpeg duplicating each image for the YUV video? Thanks a lot in advance! - Chris