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

[Baptiste Coudurier]

On 05/05/2011 04:34 PM, sean darcy wrote:
> On 05/05/2011 04:36 PM, Baptiste Coudurier wrote:
>> Hi,
>>
>> On 05/05/2011 01:19 PM, 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?
>>
>> progressive. By default encoding is 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."
>>
>> Correct, it is progressive. Use -vf yadif instead of -deinterlace
>> Deinterlacing may be a bit destructive, especially if the input is _not_
>> interlaced.
>>
>>> [...]
>>>
>>> Given this note about losses, am I right we should never deinterlace?
>>> Almost never? When is deinterlacing required/better?
>>
>> You have options:
>> if the receiving end playback interlaced (CRT tv):
>> encode interlaced
>> else if the receiver is going to deinterlace if the file is marked as
>> interlaced and you trust this deinterlacer, then you may encode
>> interlaced (deinterlacing will take cpu time)
>> otherwise you should deinterlace yourself using a good deinterlacer.
> 
> Right. I knew that! Just passed right out of my mind, though.
>>
>> I suggest always deinterlace using -vf yadif if the source content is
>> interlaced
>>
> 
> Well I found http://guru.multimedia.cx/deinterlacing-filters/
> 
> so I thought I'd try:
> 
> -vf "yadif=3:0,mp=mcdeint=2:0:10"
> 
> (dv is bottom-field first, right?)
> 
> That generates a lot of perplexing output:
> 
> [snow @ 0x230df40] pass:4mv changed:1384
> [snow @ 0x230df40] pass:0 changed:1083
> [snow @ 0x230df40] pass:1 changed:407
> [snow @ 0x230df40] pass:2 changed:147
> [snow @ 0x230df40] pass:3 changed:50
> [snow @ 0x230df40] pass:4 changed:17
> [snow @ 0x230df40] pass:5 changed:11
> [snow @ 0x230df40] pass:6 changed:2
> [snow @ 0x230df40] pass:7 changed:1
> [snow @ 0x230df40] pass:8 changed:1
> [snow @ 0x230df40] pass:9 changed:1
> [snow @ 0x230df40] pass:10 changed:1
> [snow @ 0x230df40] pass:11 changed:2
> [snow @ 0x230df40] pass:12 changed:2
> [snow @ 0x230df40] pass:13 changed:2
> [snow @ 0x230df40] pass:14 changed:0
> [snow @ 0x230df40] pass:4mv changed:1864

This is some debug messages, ignore them.

> I realize the filter comparison is from five years ago, and yadif may
> have changed significantly since then. Does mcdeint still add anything
> to yadif?

I think nothing has changed much since then :)

-- 
Baptiste COUDURIER
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