Data Rate

[Rafael Amador]

Hi Steven,
I will try to find for you an article where this topic is explained.
Basically the thing is that 100 Mbps would be the (more or less) data rate when working with the bigger size and higher time-base. I guess that 1440×1080 i60.
Rafael

http://www.nagavideo.com

[Andy Mees]

Hey Steven

DVCPRO HD’s maximum saturated datarate is 100 Mb/s (little b) which is Megabits per second .. there’s 8 of those to every MegaByte (big B) so if its maxed out then its 12.5 MB/s (Megabytes per second).

If your frame size and frame rate is only 720p24 then you’ll not be maxing out the codec datarate so you may well see the lower datarates you’re reporting … that said I’m not using DVCPROHD or 720 HD framesizs so beyond the theory I can’t be certain the specific datarate your seeing is necessarily typical.

Hope its helpful
Andy

[Jeremy Garchow]

As has been touched on here:

Dvcpro hd is not a variable bit rate codec. What does that mean? That means every frame is the same size no matter what the resolution/ frame rate. So 100 mb/sec is based on 1080i/60(50) or 720p60(50). That means shooting at the max resolution/frame rate for the given frame size will yield a file that achieves the data rate of 100 mb/sec. Now if you start shooting at lower frame rates, then the maximum data rate lowers as each frame is still the same size (read: I-Frame). This is a good thing as then it’s much easier to compress the next frame as it is predictable. Video is almost always about the next frame. That’s why you find so many sequels.

Bad jokes aside, you take a 720p60 signal and divide that by 720p24 you will find that it will take about 60% less space as you have fewer frames, hence your data rate is about 60% lower.

Que Syrah Shiraz.

[Andy Mees]

Video is almost always about the next frame. That’s why you find so many sequels.

Oh man … thats cheesy 🙂

[Jeremy Garchow]

Hey, well, at least you smiled.

https://www.birdwatchersdigest.com/blog/uploaded_images/AngusCheesy-743049.JPG

[Bob Zelin]

https://www.dulcesystems.com/html/video_space.html

this is the chart that I live by. As per Dulce’s chart –
DVCProHD 13.9 Mb/sec (at 60)
DVCProHD 720p at 24 5.7 Mb/sec

and all I care about these days –
Apple ProRes422HQ 1920×1200 at 60 (220mb/sec) – 26.8 Mb/sec.

SD 10 bit is about the same size as Apple ProRes422HQ for HD.
So if I can get 30Mb/sec, then I am happy.

Everyone should understand that to get SUSTAINED performance, (for an hour long show), you need a higher bandwidth that this to get your system to work. This is why FW400 drives don’t work out in real life.

Bob Zelin

[Steven Beers]

Thanks so much guys, I knew I was missing something obvious. I was always bad with capital letters in English class.

[John Gonzalez]

The files are being generated by a Deck Link Pro card that is in an HP server.

.DV files ARE encoded with the dv codec it is just a raw stream that supports 2 embedded audio tracks. QT .mov files are just a wrapper that can contain different codecs (essence) in our case that essence is a DV stream with separate audio neatly wrapped or packaged in a .mov.

Problem is that FCP does not appear to work well with a .dv stream when audio is added to it.