How much video on 25gb disk?

[archp2011]

I have a Canon T2i and just ordered an internal blu-ray writer for my HTPC. I'm wondering how long a full HD video I will need to fill a 25gb blu-ray disc. I am currently using Corel Videostudio X3 for video editing and encoding to hard drive and find that a 2gb MP4 file at 1080p video on my drive is typically over 2 hours long. What can I expect when I choose to burn to blu-ray disc?

[Baldrick]

It depends on the bitrate. You can just use same as your source video so 2gb=2hour. And you probably don't have to reconvert at all if it's already blu-ray compatable ( www.videohelp.com/hd#tech ).

[archp2011]

Thanks for the reply. I assume you're saying that the source bitrate will allow ~2 hours on a 25gb disk. I will let you know about my experiences when I get the blu-ray writer and -RE disks which will likely be another month.

[Baldrick]

2gb/2hours = 25 gb/25hours.

[jagabo]

1080p at 1 GB/hr? That must look pretty poor unless it's a slideshow.

[archp2011]

Sorry, that 2 gb clip that I said was over 2 hours long was 720p not 1080p. Not that this would have made a big difference, though. It looked as good as it looked from the camera to me - a Jazz point and shoot. Corel Videostudio X3 produces a 10 minute clip from my T2i 1080p/30 video that's only around 500 to 600mb in size which is still pretty small. The T2i clips are around 45 or 46 mbps from the camera according to Mediainfo. I was thinking that I'd be lucky to get 2 hours on a 25gb blu-ray disk if I keep this same bit rate. I understand that even commercial blu-ray movies are only around 30 mbps on 25gb disks.

[jagabo]

file size = bitrate * running time

for example, at 30 Mbps:

file size = bitrate * running time
file size = 30 Mbps * 2 hours
file size = 30 Mbps * 7200 seconds
file size = 216,000 Mbits
files size = 27,000 MBytes
file size = 27 GB

In general the following properties require more bitrate to retain visual quality:

larger frames
higher frame rates
anything that cause consecutive frames to be different -- noise, motion, fades, flickering lights...
bright, high contrast, details

So you can put as much video as you want on a disc. But quality will degrade once you get past a certain point. That point will vary depending on the properties of the video.