Re: [Mjpeg-users] Compare yuvscaler and y4mscaler

[Steven M. S. <sm...@2B...>]

Howdy -


On Mon, 5 Jan 2004, Matto Marjanovic wrote:

	Thanks for chiming in!

> I believe that for downscaling, yuvscaler defaults to its "RESAMPLE" mode,
>  which is similar to y4mscaler's "box" kernel.  The other yuvscaler mode

	Yes, that's what I thought - the usage summary from yuvscaler says
	resample is what it uses by default for downscaling.

> No (and not really)... the current default is 'linear'; a better would be
>  'cubic', and even better is something like 'sinc:8'.  I haven't had the

	I'm using sinc:8 - a carryover from the previous option of 
	'sinc8lan' (I think that's what it was called in y4mscaler 0.5.x).

> You need to add "-I norm=NTSC" *before* the "-O preset=SVCD"; options are
>  evaluated in order.  (This is not clear in the manpage.  I'll fix that.
>  In fact, it might make more sense to evaluate all -I options before any
>  -O options...)

	Ah ha - that's the part I didn't realize.  It's not clear which
	programs process their args once in order and which ones make
	multiple passes.

> The 'norm' is inferred from the frame rate (not the frame size).  mplayer

	Oh ok - I thought it might be keying on the frame size since 480, 240
	are NTSC as a rule and 576 and 288 are PAL usually.

>  has provided a lame approximation to "24000/1001", and y4mscaler is looking

	Sigh yes, they still haven't managed to get that right and I'm 
	tired of fighting 'em to fix it.   That's why I came up with 
	tools to strip off the header and allow me to recreate it correctly.

> 
> After that, y4mscaler will probably complain that it doesn't know the
>  sample aspect ratio (SAR) of the input --- and, really, it can't do much

	And don't bring that topic up on mplayer or ffmpeg mailing lists
	unless you are prepared for a flame fest (and then settling on
	72:79 instead of 10:11)

> If this is just some bootleg movie warez, it's probably in pretty sad shape
>  as it is, and no one will notice anyway; just say "-I sar=1:1".

	The source as I recall was a .AVI file so it was likely created
	as a quicktime movie, etc and thus 1:1 is the SAR and "-I sar=1:1"
	is the correct thing to use.

	Cheers,
	Steven Schultz