On Sat, 2004-11-06 at 16:47, Steven M. Schultz wrote: > On 6 Nov 2004, scott wrote: > > > I doing this little mod to y4mshift to try and correct some vertical > > shaking in recording from a VCR and I have got to the point where I now > > You may want to look at 'y4mstabilizer' (in the CVS version of > mjpegtools) - perhaps it will do some of what you want. >
That's interesting, I'm going to put some of my code in there instead of y4mshift. I want a specific vertical shift (im my case 0 or -1 or -2 depending on the frame) (never any horizontal) so I'm going to put in my dumb calculation to get the vertical shift which might work better/faster than the algorithm that is already there. I fear that if I have several frames in succession which have dropped the currently algorithm will tend to let them creep downwards, which I don't want. > > I think I understand that 4:2:0 has (for each square of 4 pixels) 4 Y > > values, 1 U, and 1 V value. But what happens in the uchar **yuv arrays > > for interlaced material. I presume that the first row of U/V values > > 4:2:0 is, as you noticed, subsampled in BOTH the horizontal _and_ > vertical dimensions. > > > Is that correct and if so are there any algorithms in the library to > > handle shifting by numbers that are not a factor of 4? > > Not if you're doing the processing in 4:2:0 - two fields x the vertical > subsampling factor of 2 = 4. > > What you can do is supersample the data up to 4:2:2 or even 4:4:4, > perform whatever manipulations you want, and then subsample back to > 4:2:0 > That makes sense. > y4mscaler can do that for you with the option "-O chromass=422" or > "-O chromass=444". Then to convert back to 420 before going into > the encoder you'd use "-O chromass=420_mpeg2" > That sounds easy :-) > The other thing which may make life simpler is to deinterlace the > material with 'yuvdeinterlace'. Deinterlaced supersampled (to 4:4:4) > data may be the simplest/easiest form to work with for stabilization > purposes. > Yes, it would be easier except that every 5 frames or so the field order is incorrect and needs to be swapped. I'll have a look at y4mscaler -S mode=LINESWITCH so see if I can make it only line switch on a function I have. > Cheers, > Steven Schultz > > > > ------------------------------------------------------- > This SF.Net email is sponsored by: > Sybase ASE Linux Express Edition - download now for FREE > LinuxWorld Reader's Choice Award Winner for best database on Linux. > http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click > _______________________________________________ > Mjpeg-users mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/mjpeg-users ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
