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Mathematical Check
I am trying to check the math on the amount of time per 8 GB card using DVCPRO HD codec. But it’s not working. Could someone point out my flaw?
On a 8 GB card you should get 8 minutes @ 100 Mb/s. This is in the HVX manual.
Therefore,
8 min * 60 sec/min = 480 sec //Uniform Units
100 Mb/sec * 1 Gb/1024 Mb = .01 Gb/sec //0.0977 Gb/sec
.01 Gb/sec * 1 GB/8 Gb = .0125 GB/sec //Bits to BytesFinally,
Data Rate * Advertised storage in Time = Total bytes
480 sec * .0125 GB/sec = 6 GB
I’m sure this is an error on my part because I calculated the same thing for XDCAM, but where?
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4 Replies
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Umm- I kinda failed math in college. What is it you’re driving at?
Noah
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There are other things besides video being recorded, Audio, Thumbnails, meta-data. Basically in 1080i or 720P60 you will get about 1 minute per GB.
Best,
Jan
Jan Crittenden Livingston
Product Manager, DVCPRO, DVCPRO50, AG-DVX100
Panasonic Broadcast & TV Systems -
I’m assuming that audio is included in that bit stream since it is the same rate for tape.
Neither meta data, nor thumbnails make up any significant space, especially not 25% of the disc.
Also, I’ve calculated the same data rates for all possible recording formats the HVX provides for and those match up to my (mis)calculation.
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Actually those little extras do count…. DVCPRO HD (100) uses almost exactly 100 Mb/s for the video payload, to that add 4 x 1.5Mb/s audio channels, XML Metadata, Thumbnails, Voice Memos, Proxy info, misc P-2 house keepig stuff, and it comes about to about 120Mb/s… hence the approximate 1GB = 1 minute of record time.
DVCPRO HD (Tape has a total bit rate of about 176Mb/s….. ) so you’re lucky that P-2 doesn’t need channel coding, ECC, ITI sectors data, subcode data and numerous other life support requirements!
Cheers,
Steve Mahrer (Panasonic Broadcast)
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