capturing visual data

[johnson322]

I work in Visual Effects and my company has recently bought an HVX to record elements for fx production. I have a few questions that are difficult to find clear answers for and are hoping that you might be able to decipher my questions and point me in the right direction.

1. I read that the camera is always recording 1080 60p and converts that data into all of the other formats before being recorded. Is this true? If not, what is the original recording format prior to any conversions?

2. Which external drive solutions will best capture this original data? Are there any drives that will capture this data as well as the P2 cards can?

3. Are all the formats 4:2:2?

I am really only interested in progressive native formats.

Thanks in advance. :dankk2:


Justin Johnson
Compositing Supervisor
Luma Pictures

 

[andy_starbuck]

Q1: "1080/60p or the original recording format prior to any conversion?"

The raw data from the sensors is not 'recorded' prior to size reduction and encoding. There is no method built into the camera for accessing this raw un-encoded data. You have to work with the formats that the camera does record in, which are variations of 1080, 720p, and 480i formats. There is no 'original recording format prior to any conversion'. I don't know the statistics of the sensors, but it is not significant since you can't access that data anyway. The highest resolution format is 1080, and you can record in 1080/24p.

Q2: External drive for capturing 'original data'?
Since you can't access the raw sensor data from the camera, you can't record it, drive or no drive. As far as capturing 1080 or 720, there is no problem capturing most formats over firewire to a special device such as a Firestore, or to a computer, using a non-linear editor. There are certain native formats (720pN) which can only be recorded to P2 cards because they lack the timing characteristics for transport over firewire.

Q3: Are all the formats 4:2:2
The camera records in DV, both to miniDV tape and to P2 card, which is 4:1:1. The camera records 480i in DVCPRO50 to P2 card (not to tape) in 4:2:2. All the HD recording formats use the DVCPROHD codec which is 4:2:2.

Q4: Progressive Native formats?

720p/24pN, 720p/30pN

For visual effects you will find that 720p is often quite enough. For chromakey work people have written about using 1080 formats for extra resolution, or, if your output is standard definition, recording in 480 progressive DVCPRO50, to avoid the extra compression of the HD codecs. You cannot record Native formats over firewire. So you have to record these formats with a P2 solution.

You can find a lot of information using the DVXuser search capability.

Hope that helps.

 

[johnson322]

thanks for the answers to my questions.. I spent a few hours looking around the forums. With your answers and my research on this forum I have been able to formulate more percise questions.

1. Can I record 720/60p, 1080/30p, and 1080/24p directly to a mac via firewire and Final Cut and does drive speed of the mac effect this capability? (if i know its possible i will eventually figure it out)

2. Is there any reason that I would need to do a pull down on the 720/60p to get a "naitive" type of sequece. (Cause when I try I get duplicate frames)


3. I cannot find any percise explanation on these procedures. Are they in the HVX book?

4. which formats do not require any pulldown at all, if any?

 

[andy_starbuck]

1. Can I record 720/60p, 1080/30p, and 1080/24p directly to a mac via firewire and Final Cut

As far as I know, you can record these formats over Firewire. Only "native" modes can't be recorded over Firewire.

Does drive speed of the mac effect this capability?

I don't know. I've recorded in 720/60p and 1080/24pA via firewire to a dual G5 and to a 12" powerbook without dropping frames.

2. Is there any reason that I would need to do a pull down on the 720/60p to get a "native" type of sequence.

Not on 60p, that I'm aware. You might want to use a Frame Rate Converter to drop out 720/60p frames to create motion effects. But that's not pulldown removal.

3. I cannot find any percise explanation on these procedures. Are they in the HVX book?

You should DEFINITELY get and read the HVX Book. It will provide detailed insight into many of the questions you are asking. It won't tell you procedures for using editing software. But you will understand the video technology. And that will help a lot.

4. Which formats do not require any pulldown at all, if any?

This is sort of a complicated question.

Pulldown is not an issue in anything with '25' or '50' (PAL) or '30' or '60' (NTSC). It is only an issue when something is recorded at 24 frames per second and topped up to 30 frames per second or 60 fields per second (NTSC).

480i/24pA and 1080i/24pA require pulldown removal to work with the native frames on a 23.98 timeline. 480i/24p and 720p/24p, and 1080/24p (without the 'A') do not require pulldown removal if you are working with them on a 29.97 timeline. You may optionally remove the pulldown to work with them on a 23.98 timeline. 720p/24pN doesn't have pulldown in it, so there is nothing to remove.