[FFmpeg-user] ntsc-dvd doesn't default to interlaced.

[Andy Civil]

On 2013-07-27 10:12 PM, Mike Brown wrote:
> On Sat, Jul 27, 2013 at 09:56:35PM -0400, Andy Civil wrote:
>> The video starts from my Sony HX5 as 1920 x 1080 x 30i. It's then
>> deinterlaced by a commercial video editor to 1920 x 1080 x 60p. Every frame
>> is different.
>
> I'm curious as to why you would want to do that.

Because I first tried the interlace-aware scaler, and I was unable to make it 
also switch from TFF input to BFF output. (My camera produces TFF video, being 
the HD standard, but a BFF DVD-video is more common. Yes, I know that you can 
also have a TFF DVD-video, but I want my output to be as 'normal' as possible.)

>
> I have to admit that I do not know what all ffmpeg can do.  But, IMHO, the
> best way to go from 1080i to 480i is to rescale each 1080i field to the
> 480i field.  By going to 60p first, each of the frames is a "guess" as to
> what a full frame would look like from a half frame.
>
> By going directly from 540 lines to 240 lines, you skip the guessing game.

Because it's being scaled, some lines will be directly taken from the input, 
some will be guesses, depending on how they fall, no? You can only eliminate 
guesses if the output size is a factor of the input size e.g. 480 -> 240.

I'm not saying that I'm doing it the best way, nor that my intermediate file is 
the smallest, but it works and I'm confident in the quality of the output. 
(However, I do realise that if I accepted 30p as being 'smooth enough' then I 
could probably get a sharper picture, due to improved compression characteristics.)

--
Andy