Weirdness!! - Data Rate/Import/720.24pn

[Director Doug]

Here's a weird one... I used my new HPX500 to videotape an interview - using 720/24PN. When I sent it out to tape via FireWire to a Panasonic AJHD1400, there were segments of the clips where the video stopped, and the audio continued...
So, having already imported them into Final Cut as clips, I then hooked up the camera directly to my Final Cut Pro G5 via FireWire, and imported replacement clips directly from the card still in the camera, using the P2 import tool in FCP. That means, I did not download the entire card to the computer as a file (I was only using five clips out of twenty or so...), I just imported the segments of the clips I was going to use.

The clips came in fine, no video stops, but there were two weirdnesses... first, the video rate was listed as 23.98 but the compressor was listed as DVCPRO HD 720p60, and the data rate was only 5.7mbps. What did I do wrong...?

On top of it all, my footage was 'soft'.

Any help will be appreciated...

[N. Adam Smith]

It sounds like in both instances you're pulling the footage directly from the camera via firewire... I don't have the camera yet (20 more days for financing to go through!!) but in some of the .pdf literature I have there is this note...

The IEEE 1394-compliant DVCPRO (6-pin) output connector lets you output all HD/SD compression streams without decoding.*

And at the bottom...

* Output is not possible in 720P native mode (24pN, 30pN, 25pN).

It sounds like if we shoot in the camera-native modes we can't output the footage via firewire. Which sorta sucks, obviously... since it's the shooting mode with the most efficiency and fancy frame-rate tricks. =(

Note that the native shooting rates are all true 24 (23.98) fps recordings, while the non-native formats either record at 60i/60p or use pulldown to pad the framerate up to 60i/60p... so I'm guessing something about true 24p and firewire don't jive.

[Luis Caffesse]

The compressor will always say 720P60, because that is what the compressor is doing - just so happens that on the P2 cards you can choose not to record duplicate frames that need to be created in order to fill the 60fps requirments of the 720P DVCProHD codec. But the compression is always the same - 100mb/s over 60fps. Because of the fact that the DVCProHD codec is interframe codec, every frame is compressed independently (unlike HDV or other MPG based codecs that share compression over a Group Of Pictures). So, you've got 100mb/s for 60 frames - that means each frame is roughly 1.6mb.
So effectively when shooting 24PN you wind up wiht a bitrate of 40mb/s.
Which is roughly around 5mB/s (megaBYTES per second as opposed to megabits).

My point here is that the compression is always the same, it is always 720P60.

So just keep an eye on your frame rate to make sure you're getting what you want, but the compressor in FCP will always say 720P60 (and 720P50 in PAL land).

As far as the firewire port - I'm going to take a small leap here and assume that the HPX is going to behave the same as the HVX when it comes to PN modes. It seems that Panasonic wants to keep the signal coming out of the firewire a standard 720P 60fps stream. Tape based machines wouldn't know what to do wiht a native 24P signal (as you found out) - DVCProHD tapes always run at 60fps when recording 720P (recording duplicate frames to make up the difference). So - keeping with the standard - Panasonic only allows 'full' streams to go out of the firewire port. No native modes will output via 1394. This is why when recording with the FireStore, for example, you have to set your camera to 720P mode, not PN. Otherwise there is no signal to record.
Same goes for tape based media (as far as I know).

Of course an added benefit for Panasonic was that for a short while the only way to record native frame rates was on P2 cards.



So...you did nothing wrong.
Well...except for the footage being soft...that's all youl



(hope this helped - not sure if i made much sense...i'm very tired)

[Director Doug]

Thanks for the replies! You made it all seem to make sense... and I'm sure the 'softness' was the lack of a back focus adjustment... my bad!