35 Mbps VBR - does this number define average or maximum bit rate?

the maximum bitrate.
but don't try to compare XDCAM with the 25Mbit CBR of HDV.

"but don't try to compare XDCAM with the 25Mbit CBR of HDV."

Why not ? Please explain.

If 35 VBR defines the maximum rate - does this mean that, depending on the content of the image, the AVERAGE bit rate of 35 VBR mode can drop significantly even below 25 Mbps?

Jackpot Question ! Michael -

Eager to see feedback on this one -

No, i'm sure it can't drop under 25Mbit.
The comparison between HDV and XDCAM is non-permissible because XDCAM uses a better codec. I tested my 350 under several conditions. I came to the following conclusion:

18Mbit XDCAM HD = 25Mbit HDV
25Mbit XDCAM HD compares to a fiktive HDV50
an the 35Mbit HD is nearly DVCPROHD.

Thats my opinion ;)

an the 35Mbit HD is nearly DVCPROHD.Robert, have you seen some of the tiffs in xdcam ex forum? Clearly they're grabs from some blueray disc...But...have you seen some macroblocking artifacts in Xdcam 350 like those tiffs at 35mb ? In your experience at which datarate xdcam could show artifacts like those tiffs? thanks

Robert, have you seen some of the tiffs in xdcam ex forum? Clearly they're grabs from some blueray disc...But...have you seen some macroblocking artifacts in Xdcam 350 like those tiffs at 35mb ? In your experience at which datarate xdcam could show artifacts like those tiffs? thanks

I'm surprised there has been little discussion about those tiffs.
Some look good, and some look really bad.
Why the macroblocking if the codec is supposed to be better than HDV?

"If 35 VBR defines the maximum rate - does this mean that, depending on the content of the image, the AVERAGE bit rate of 35 VBR mode can drop significantly even below 25 Mbps?

as far as I understand it Michael, yes it can drop below 25 Mbps.
you have to think of it in terms of the mathematics. where fast moving high detail images will need all 35 Mbs to encode the data, static low detail images will need significantly less, perhaps less than 25 Mbs (maybe even a lot less) ... but so what? what would be gained by storing redundant image data? the 25 Mbs CBR of HDV dictates that a full 25 Mbps of image data be retained even when that data is not needed, this is the down side to any CBR format, MPEG or otherwise.

mysterious ;).

Some month ago, i think, i read the specs fpr the XDCAM HD HQ - Mode, where it says max bitrate is 35, average is 30, and minimum is 25.
Yes, if i find some free time, i'll post a tiff of the 350 in HQ-Mode.

... what would be gained by storing redundant image data? the 25 Mbs CBR of HDV dictates that a full 25 Mbps of image data be retained even when that data is not needed...
Andy, I thought for more static images there is not redundant data stored but a lower compression applied. And that might be visible. Isn't that so?

Yes, if i find some free time, i'll post a tiff of the 350 in HQ-Mode.
Please do, Robert.

The comparison between HDV and XDCAM is non-permissible because XDCAM uses a better codec.

Hhm ... I found this in the EX brochure:

"This highly efficient “MPEG-2 Long GOP” codec – that is also
adopted in the XDCAM HD and HDV 1080i series of
products – enables users to record stunning-quality HD
video and audio over a long period of time by efficiently
compressing the data."

That doesn't sound like a big difference in quality of codecs, does it?
Anyway, I'd be pleased to learn that the XDCAM codec looks better than HDV, Robert.

Anyway, I'd be pleased to learn that the XDCAM codec looks better than HDV, Robert.

We already learned this in March 2006 when the XDCAM HD cameras were first released. The XDCAM EX expands on that already good looking image.

The 35mb VBR codec can go up or down as needed. I was even told by a Sony engineering type it can briefly spike a little higher than 35 mbs under certain scenarios.

The VBR is more efficient for storage capacity vs. quality. Large, static, unmoving, solid color objects can be compressed more without a loss of visual quality.

-gb-

I haven't seen ANY macroblocking on any of the footage we have shot over the last year. XDCam HD code is very solid and VERY different to HDV.

You can't comment on .tiffs posted on the web you have to see original footage.

I haven't seen ANY macroblocking on any of the footage we have shot over the last year. XDCam HD code is very solid and VERY different to HDV.

You can't comment on .tiffs posted on the web you have to see original footage.

Well stated, Steve. And very true!

My favorite XDCAM HD story is the one told about the big wigs evaluating XDCAM HD and viewing a freeze frame of a helicopter in flight. One of them tried to point out the macroblocking artifact on one of the main rotor blades.

Fortunately for all, an astute observer with aviation knowledge pointed out that what they were in fact seeing, was the trim tab on the rotor blade!

-gb-

I haven't seen ANY macroblocking on any of the footage we have shot over the last year. XDCam HD code is very solid and VERY different to HDV.

You can't comment on .tiffs posted on the web you have to see original footage.

Steve, I respect what your saying, but a lot of times with HDV I don't see these artifacts until I slow the video sequence down or look at still frames.

Also, when you start to push your video in post, issues may start to appear.

Having said that, have you looked closely (still frame) for any macroblocking with the XDCAM HD @ 35MB? I've heard it clean. Since it's the same codec, I can't imagine why the EX1 would be any different

In the end, I do realize we will be watching full motion video and the problems may be a bit masked, but this bothers me, and I'm sure a lot of other mpeg camera operators on this forum.

You're correct about the tiff files. We DO NOT know how these were extracted.

You're correct about the tiff files. We DO NOT know how these were extracted.

For some reason, all the tiff files were saved by Adobe Photoshop CS3 - am not sure what to make out of it, but this what I can see in their properties listings.