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-   -   100mb or 50mb? (https://www.dvinfo.net/forum/convergent-design-odyssey/139733-100mb-50mb.html)

Jerry Lee December 16th, 2008 12:29 AM

100mb or 50mb?
We had tried to import the MOV files(1080i60,1920*1080) ,which were recorded from SONY EX3 by HD-SDI out to flash xdr at 100MB rate, to fcp,but when we check the item properites in fcp ,the compressor is XDCAM422 HD 1080i60 (50Mb/s)and the data rate is12.2MB/sec.What we wonder is that the original rate is 100MB but fcp shows are different.What's up there?How do I know the real rate of the MOV files,which were recorded from SONY EX3 by HD-SDI out to flash xdr at 100MB rate?And was the 100MB recording rate data had been compressed by flash xdr?

Paul Bryer December 16th, 2008 03:32 AM

As a straightforward calculation, 1 Byte=8 bits so 12.2Megabytes/s=97.6Megabits/s, which tells you your footage is (approximately) 100Mbps.

I'm guessing the issue here is that the support in FCP for the Sony MPEG2 codec used in the XDR and the XDCAM range was named around the flavours of MPEG2 the XDCAM camcorders use, which only go up to 50Mbps (on the PDW-700). So whilst the XDR recorded footage is 100Mbps, its labelled as 50Mbps by FCP, because it doesn't have "XDCAM422 HD 1080i60 (100Mb/s)" in its vocabulary.

The easiest way to tell whether your footage is 50Mbps or 100Mbps is to look at the data rate, not the codec name. If its around 6.25MB/s its 50Mbps, if its around 12.5MB/s its 100Mbps.

Dan Keaton December 16th, 2008 05:50 AM

Dear Jerry,

We understand your concerns.

If you select 100 Mbps in the Flash XDR, yes, you get 100 Mbps.

Paul, your analysis is absolutely correct. The proof is in the data rate.

Apple did not make any changes to support 100 Mbps, nor did they need to, as it just worked. So, in their labeling, it is called 50 Mbps, but it is actually 100 Mbps.

We are currently using 100 Mbps constant bit-rate recordings. We could have used 100 Mbps maximum variable bit-rate recordings, but we chose constant bit-rate.

Apple may label these correctly in a future release, but I do not have any inside information about their plans at this time.

I will check on why it is 12.2 MBps instead of 12.5 MBps.

Paul Cronin December 16th, 2008 08:25 AM

Jerry you can also open one of your clip files with QuickTime and look at clip properties. This will show you the 100Mbp/s.

Interesting Dan I knew the data rate was double the 50Mbp/s rate but did not know it was really at 100Mbp/s. Cool no need for me to shoot 50Mbp/s now.

Dan Keaton December 16th, 2008 08:35 AM

Dear Paul,

We do recommend using Final Cut Pro 6.0.4 or higher.


Paul Cronin December 16th, 2008 08:37 AM

Thanks Dan no worry I am on the current version.

Dan Keaton December 16th, 2008 08:51 AM

Dear Jerry,

We use, for both 50 Mbps and 100 Mbps bit-rates, constant bit rate option as opposed to "Maximum Variable Bit Rate" option. We do this to be compatible with XDCam.

While it is named "Constant Bit Rate", it still varies slightly. So at any given instant it may be slightly below 100 Mbps or over 100 Mbps.

The 12.2 Megabytes per second that you saw, versus the calculated 12.5 Megabytes per second is perfectly normal, and this value may change over time.

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