Quick Question Regarding Sample Rates

David Saraceno

David Saraceno

Moderator
Staff member
Someone posted this elsewhere:

"DVCPRO HD is 4:2:2 but 720p is down sampled from 1280x720 to 960x720, and 1080i is down sampled from 1920x1080 to 1280x1080 for 59.94i. HDV is 1440x1080 [squeezed horrizontally 1.33] and is 4.2.0"

I don't believe that's correct.

To clarify, I'm aware of the color space differences between HDV and DVCProHD, but I thought the HVX200 sampled at 1980 for 720 footage and downconverted in the cam

Can someone point me to the specs to dispute this with the HVX?

thanks
 
Last edited:
This is from Panasonic'e website:

New DSP with 14-bit A/D Conversion and 19-bit Processing
The AG-HVX200's newly developed digital signal processor for 1080/60p video signals uses 14-bit A/D conversion and 19-bit inner processing to attain unprecedented accuracy. While the camera does not record 1080/60p, it is from this capture that all other signals are made. The DSP performs a variety of adjustments, including eight types of gamma settings, for each of the R, G and B channels. It also converts the signals to HD or SD format. With a performance equivalent to the processors used in many higher-end HD cameras, this new DSP helps the AG-HVX200 deliver beautiful images in all video formats.

High-Resolution Native Progressive 1080/60p Scan
Progressive to interlace conversion, cross conversion and down conversion all start with the 1080p/60 scan. That initial 1080p Native Progressive Scan offers the highest level of vertical resolution possible at this level of camera. Keep in mind that the camera does not record this signal but uses it as a basis for all capture. The result is an HD or SD recording with a level of image quality that electronically processed scans cannot match.
DVCPRO HD: The Image and Sound Quality Broadcasters Demand Supports Multi-Codec Recording
 
It scans the chip into a 1920x1080 matrix, and all processing is done internally at 1920x1080. Then it downsamples to whatever the recording format is.

For 1080, it converts the 1920x1080@4:2:2 into 1280x1080@4:2:2 for 60Hz, or 1440x1080@4:2:2 for 50Hz.

For 720, it converts the 1920x1080@4:2:2 into 960x720 @ 4:2:2 for both regions.

For SD, it converts the 1920x1080 @ 4:2:2 into 720x480, and the color sampling depends on whether you're going to DVCPRO50 or to DVCPRO25/DV. Also, it will either do a full-frame conversion for 16:9, or a "center extraction" (cutting off the sides) for 4:3.

But regardless, all internal processing is always done at 1920x1080 at whatever frame rate you chose. So when shooting 1080/60i (or even 480/60i) the internal processing is 1920x1080x60p; the conversion to interlaced happens when it's being recorded.

Panasonic's statement on how the chips work is here:
ftp://ftp.panasonic.com/pub/Panasonic/Drivers/PBTS/papers/AG-HVX200.CCD-WP.pdf
 
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