Hi guys This is my first post in this list so hi ! Hope you could help in this as i am a begginner in the video world. What i am trying to achieve is to take a video stream, extract couple of frames, modify them (add another picture on top) and put them back in to the video stream.
This is what i do : (lav2yuv -f 1 myMovie.mov | y4mtoppm | <composite command>| ppmtoy4m -F 25:1 | strip.sh;... ;lav2yuv -f 2 myMovie.mov | y4mtoppm | <composite command>| ppmtoy4m -F 25:1 | strip.sh;) | ffmpeg -f yuv4mpeg pipe -i - -sameq -b 8500 res.mov Note: the strip.sh remove Y4M unwanted headers Everythings work not too bad except i can notice a luminance difference between frame i had extracted and the rest of the video stream. It is like a white transparent shadow (it s more visible from Quicktime Player though ...) I thought it might be the composite command (from ImageMagick) that i was doin so i removed it like this : (lav2yuv -f 1 myMovie.mov | y4mtoppm | ppmtoy4m -F 25:1 | strip.sh;... ;lav2yuv -f 10 myMovie.mov | y4mtoppm | ppmtoy4m -F 25:1 | strip.sh;) | ffmpeg -f yuv4mpeg pipe -i - -sameq -b 8500 res.mov And same result . So i concluded y4mtoppm or ppmtoy4m is the culprit (or both) . I know the subsampling and colorspace operations is lossy so i guess the shadow comes from this loss. ... So my question is : do u think i could more or less fix this using yuvdenoise or another tool ? Other tool like y4mscaler could help me ? using y4mtopnm would make things better (tried to use it though but it seems not to accept output from lav2yuv)? (i am not very confident in chroma things ...) Maybe , would it be possible to change the command line to make things better (ppmtoy4m parameters ... i tried many options with no luck though ...) Alternatively i though i could use YUV data instead of PPM (so i could work directly with yuv without subsampling) , i tried to extract one yuv single frame but imageMagick only displays crap. ...: So i ran out of idea and feel a little down @ this time of the nite ...:-) Would you advise me a complete different way to this ? (i heard about MPEG2 stream with only I frames ...) Thanx a lot for your attention Cheers seb ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
