[MEncoder-users] Determining proper frame rate

[L Lee]

On 11/4/09 4:13 PM, "Grozdan" <neutrino8 at gmail.com> wrote:

> 2009/11/4 Andrew Berg <bahamutzero8825 at gmail.com>:
>> Jason Simpson wrote:
>>> From your example rates, I'm guessing that you are dealing with NTSC
>>> video sources.
>>> 
>> Yes.
>>> I use the script below that checks twenty one-second samples of
>>> video at various spots throughout the input stream to
>>> pseudo-statistically determine if the video is primarily telecined.
>>> 
>>> Hope this is helpful.
>>> 
>> Seems it isn't telecined according to your script, which is exactly what
>> I thought. Thanks.
>> 
>> 
>> While we're on the subject, I have material that I know is telecined at
>> 60000/1001fps and I want it at half that (it's on a network that does
>> 720p at 60000/1001 and the material is originally 1080i at 30000/1001).
>> -ofps 30000/1001 doesn't work. There's some discussion about 60fps
>> telecined material on the list, but I didn't quite understand it and I
>> think it's for getting 24000/1001fps anyway.
> 
> Have you tried with filmdint? It can scale down frame rates with its
> io option, eg filmdint=io=60:30 -fps 60000/1001 -ofps 30000/1001. Or
> are you just trying to reduce the frame rate but preserve the
> telecine?
> 

I was fooling around with some of this today. By default, using the scale
filter for a size A:B (defaults to same as scale=A:B:0, I think) yielded
deinterlaced output if I used -ofps 30000/1001. But I know my source is
telecined, so to get output that's deinterlaced at the NTSC frame rate, I
appeared to have two choices, neither of which I liked very much, because
either way whenever there's smooth continuous motion in passages with the
slightest amount of edge contrast, it's like getting slapped six times a
second.

Using most deinterlacing filters, I get two combed frames at the same
position in every consecutive five, and using, for example,
filmdint=fast=0/io=30:30, I get a pair of duplicate frames at the same point
in every consecutive five. All my routines were using -ofps "30000/1001",
but none contained "-fps". I don't really know if there's a way to get
telecined sources to come out at 30 fps without either two duplicates or two
combed frames of every five, but I doubt it. Maybe some filters or options
can mask it better than others. (I haven't found a perfect one yet, but I'm
all eyes if any of you know of one.)

Anyway, all I had to do to get pullup using the filmdint routine was to
change "30:30" to "30:24", and "-ofps 30000/1001" to "-ofps 24000/1001", and
I didn't really have to change the -ofps value, because changing the
filmdint value changed the output frame rate even without changing anything
else, but I didn't want to leave the misleading "-ofps" option in the
command line, of course.

Laine Lee

Laine Lee