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#1 |
Major Player
Join Date: Dec 2005
Location: Kelkheim, Germany
Posts: 375
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35 Mbps average or maximum rate?
35 Mbps VBR - does this number define average or maximum bit rate?
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Michael |
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#2 |
Regular Crew
Join Date: May 2007
Location: Graz, Austria
Posts: 44
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the maximum bitrate.
but don't try to compare XDCAM with the 25Mbit CBR of HDV. |
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#3 |
Major Player
Join Date: Dec 2005
Location: Kelkheim, Germany
Posts: 375
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"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?
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Michael |
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#4 |
Major Player
Join Date: Nov 2006
Location: cape town South-Africa
Posts: 251
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Jackpot Question ! Michael -
Eager to see feedback on this one - |
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#5 |
Regular Crew
Join Date: May 2007
Location: Graz, Austria
Posts: 44
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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 ;) |
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#6 |
Regular Crew
Join Date: Sep 2006
Location: Italy
Posts: 26
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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
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#7 | |
Trustee
Join Date: Sep 2005
Location: Gilbert, AZ
Posts: 1,896
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Quote:
Some look good, and some look really bad. Why the macroblocking if the codec is supposed to be better than HDV? |
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#8 | |
Major Player
Join Date: Mar 2006
Location: Kuala Lumpur, Malaysia
Posts: 645
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Quote:
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. |
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#9 |
Regular Crew
Join Date: May 2007
Location: Graz, Austria
Posts: 44
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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. |
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#10 |
Major Player
Join Date: Dec 2005
Location: Kelkheim, Germany
Posts: 375
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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?
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Michael |
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#11 |
Major Player
Join Date: Dec 2005
Location: Kelkheim, Germany
Posts: 375
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Please do, Robert.
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Michael |
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#12 | |
Major Player
Join Date: Dec 2005
Location: Kelkheim, Germany
Posts: 375
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Quote:
"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.
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Michael |
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#13 | |
Wrangler
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Quote:
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- |
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#14 |
Major Player
Join Date: Feb 2005
Location: UK
Posts: 383
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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. |
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#15 | |
Wrangler
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Quote:
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- |
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