Theoretically it should work but it keeps complaining about stream specifier 'alpha' matching no stream: ffmpeg -v debug -f dshow -i video=UScreenCapture -i chroma. To end the chain I add the two outs with blend mode addition. To compose the three together, first I blend 'multiply' the alpha with the video, turning to black everything outside the white alpha(dumped into ), and blend 'multiply' the image background with the negative alpha (dumped into ). ![]() but a file in this case, called in the filter chain). Then I want to compose that on top of another input (some video input from a file or other capture device. pass2: Use internal 2pass ratecontrol in second pass mode. pass1: Use internal 2pass ratecontrol in first pass mode. Constant quantization will be always faster than bitrate, search for multi thread codec - h.264 is a good candidate - with preset ultrafast, tune fastdecode and gop size it can be faster than mpeg2 inside ffmpeg - you can try to tweak multi thread mpeg2 encoding - there is few options. outputcorrupt: Output even potentially corrupted frames.outputcorrupt. On the left is the image itself, on the right its alpha channel, shown in black and white. mv4: Use four motion vector by macroblock (mpeg4). The goal is to capture part of the screen (with UScreenCapture direct show device) where I display two images side by side (called and, or and in the filter chain). ![]() My intention is to show that 10 seconds video as a preview of the actual video in the front end, and I dont want to start sound in that. What I am looking for is a 10 seconds clip from the video which is saved at specific location without the audio part. Use internal 2pass ratecontrol in second pass mode. Unfortunately I dont have that information as I am giving a file-path. Use internal 2pass ratecontrol in first pass mode. I'm trying to achieve complex effect with ffmpeg, but I seem to be failing the syntax of -filter_complex somewhere. See the ffmpeg-filters manual for more information about the filtergraph syntax.
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