[FFmpeg-user] dv => mp4: deinterlace or not, and how?

[belcampo]

On 05/05/11 22:19, sean darcy wrote:
> I have an interlaced dv file. I'm transcoding it with x264 to mp4.
>
> 1. ffmpeg -i file.dv -an -vcodec libx264 -b <x> out.mp4
>
> If I just leave it like that, is out.mp4 interlaced or progressive?
>
> 2. ffmpeg -i file.dv -an -vcodec libx264 -b <x> -deinterlace out.mp4
>
> Here I assume out.mp4 is progressive. The ffmpeg documentation says:
>
> "The alternative is to deinterlace the input stream with `-deinterlace',
> but deinterlacing introduces losses."
>
> Is this still true?
>
> Given this note about losses, am I right we should never deinterlace?
> Almost never? When is deinterlacing required/better?
It depends, as always. If the final display is a TV, which is capable to 
deinterlacing, Most except 720p, which is rare, television broadcast is 
interlaced.
If the final display is a computer-screen or an iPhone/AndroidPhone or 
something like that, these devices don't deinterlace by themselves so 
the source has to be deinterlaced, or has the deinterlace flag set at 
the moment of display. Most people don't know that their computer 
mplayer/vlc/WindowsMediaPlayer has an deinterlace option and will see a 
very bad interlaced picture.
>
> 3. ffmpeg -i file.dv -an -vcodec libx264 -b <x> -flags +ilme+ildct out.mp4
>
> Here I assume out.mp4 is interlaced. How is this different from 1.
> above? Is it different?
>
> The FAQ mentions +alt as a flag. When should this be added? Does it hurt
> to use it all the time?
>
> sean
>
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