HPX170-Format Sizes

[Greg Harris]

Hey guys, so I started shooting a reality TV show last week. "Camera A" was a HMC150 shooting 1080 30p and Camera B was a HPX170 shooting 720 60 and 1080 30. I uploaded all of my HMC150 footage to FCP first then the HPX170's footage second. When I place the 170's clips on the FCP timeline next to the footage from the 150 I was forced to do about 2 hours of rendering for just the 170's clips. I didn't really understand the need to render, those cameras are pretty similar minus the p2 factor. It was my first time using p2 footage. When I looked at the info of the clips shot on the 170 the format size says "960x720" for stuff shot "720 60p" and "1280x1020" for clips shot in 1080 30p. On the clips shot on the HMC150 the sizes are what I would expect them to be for 1080 30, "1920x 1080". Can someone help me here and explain why this is?

Thanks

[Dan Brockett]

Hi Greg:

Forget raster sizes and frame rates, you are using two different codecs. The 150 outputs AVCHD and the 170 outputs DVCPRO HD. AVCHD is a long GOP 4:2:0 full raster codec, DVCPROHD is an intraframe 4:2:2 abbreviated raster codec. Placing AVCHD and DVCPRO HD on the same timeline would usually require rendering.

FCP automatically compensates for the DVCPRO HD abbreviated raster format. When you display those 1280 x 1080 clips in FCP, it automatically stretches it to fill up the 1920 x 1080 raster. the same as HDV which is also an abbreviated raster codec.

You could transcode both the AVCHD and the DVCPRO HD clips to ProRes and avoid all of this mess but that too would take time. But that is what most FCP editors would do as ProRes is superior to either AVCHD or DVCPRO HD because it is 10 bit intraframe full raster and you can use any of the five flavors of ProRes based upon your needs. Other software like the new Premier can display and edit mixed codec timelines without rendering with it's Mercury Playback engine. I think the new FCP X will do the same when it ships.

Dan

[Greg Harris]

Thanks Dan.

But why when I click the information button on those clips does the size of what is supposed to be 1080 30 shown as "1280x1020" and not "1920x1080?

[John Wiley]

Because they are 1280x1080. The DVCPRO-HD pixels have a wider aspect ratio (they are rectangle instead of square) so that when played back in your NLE, it looks exactly the same size as 1920x1080.

It's the same method which has been used for decades when working with widescreen DV, HDV, and even anapmorphic film workflows.

If you want the footage to display as 1920x1080 then you'll need to transcode it to ProRes. However this will not gain you any extra sharpness, it will just re-package those existing rectangle pixels into square ones. Once you've transcoded all your footage though, it will cut together much better on the timeline.

[Greg Harris]

Ok, thanks john.