[MEncoder-users] compression: 1080i versus 720p

[Raimund Berger]

Andrew Berg <bahamutzero8825 at gmail.com> writes:

> On 12/20/2009 1:51 AM, RC wrote:
>> When you deinterlace the 1080i video, you're reducing it to 30fps.  720p
>> is typically 60fps, which has more similarity to interlaced video.
>>
>> So, if you don't deinterlace the 1080i video, you'll probably see them
>> using a higher bitrate.
> What does deinterlacing have to do with framerate? It's true that (when
> it comes to TV broadcasts in the US) 720p is typically 60fps but 1080i
> feeds are 30fps whether they've been deinterlaced or not.

I guess he wanted to diifferentiate between deinterlacing to 30fps and
deinterlacing to 60fps, which in fact some people do. Because, after
all, 1080i has no actual fps, as it has no frames but just fields. So
you can say the lower bitrate is actually due to the loss in vertical
resolution that you get when deinterlacing to 30fps.