[FFmpeg-user] -pix_fmt yuv420p and deinterlacing

[Marton Balint]

On Sun, 26 Feb 2017, Katherine Frances wrote:

> Hi Martin,
>
> Oh! Thanks for letting me know. I just assumed the conflation of the two
> things here.
>
> But then, how are my output videos becoming deinterlaced?

Probably they are not.

>
> Inputs are uncompressed v210 in MOV. They're definitely interlaced, as
> they're digitized from an analogue source (using an AJA ADC) with all
> correct setup.
> And outputs are definitely progressive, at least according to MediaInfo.

Mediainfo only shows the metadata, in reality the content is most probably 
interlaced.

>
> I'm just using a basic script, for example:
>
> ffmpeg -i uncompressed_master.mov -c:v libx264 -pix_fmt yuv420p -c:a
>> libfdk_aac -b:a 128k access_copy.mp4
>
>
> So how are my MP4s becoming deinterlaced? Is it a result of declaring MP4
> as the output container? I thought that MP4s could contain interlaced
> content - am I wrong about that?
>

AFAIK ffmpeg does not do automatic deinterlacing based on container 
features, so even if MP4 were progressive-only (it is not), ffmpeg still 
would not do automatic deinterlacing.

The fact that the interlaced metadata is not reflected in the output can 
be caused by a number of reasons, either the source file is missing the 
interlaced/progressive metadata as well, or ffmpeg simply does not support 
propagating it to mp4.

In any case, if you want to deinterlace, use a filter, like yadif.

Regards,
Marton