H.264 file size for 1 hr of HD video

Question

I'm looking for an order of magnitude estimate for expected on-disk file size for 1 hour of H.264 encoded HD video transcoded from HDV (HD on a MiniDV tape). I want to archive approximately 100 hours of such content and want to figure out whether I'm looking at a big hard drive, a multi-drive unit like a Drobo, or an enterprise-level storage system.

Edit

To clarify from several good comments, I am developing the software that will use this archived video and will also manage the transcoding from HDV to compressed format (using QuickTime on OS X). This question is for gathering hardware requirements. The video is from HDV and the transcoding does not have to happen in real time. I will not be streaming the video, so I'm looking for compression that maintains as much information as possible form the HDV content. The original HDV video is interlaced, but I can deinterlace it if that would help either file size or quality of the H264 compressed output.

Answer 1

Around 4gb/hr is quite common.

Answer 2

For a good quality x264 encoding of 1060i, done by a computer, not a mobile device, not in real time, you could use a bitrate at about 5 MBps. That means 2250 MB/hour of encoded material. Recommend you deinterlace the footage and compress as progressive.

Answer 3

It is whatever size you want it to be, the only thing that changes is quality. If you intend it to be played back on a non-PC device (or a slow PC), you may need to respect a certain profile (standardized set of compression settings that ensure a fixed device can play back the content).

You can see the main H.264 profiles at Wikipedia

While it is highly subjective (and highly dependent on the content being compressed), it is claimed that H.264 can achieve the same quality as DVD MPEG2 using half the bitrate.

Answer 4

It would be a couple of gigs per hour.

MPEG-4 (of which H.264 is a sub-part) define high quality as around 4Mbps. which would be 1.8GB per hour.

This can vary depending on the type of video and the type of compression used.

Answer 5

You need to know the bitrate.. Then it's simply bitrate (bits per second) multiplied by number of seconds..

HDV is 25Mb/s, so non-transcoded it would be (I think)..

25 mbits * 3600 sec = 3.125 MB * 3600 sec = 11250 MB*hr ~ 11 GB per hour

The same applies with h.264 footage, although the above might not be as accurate (being variable bitrate and such)

I want to archive approximately 100 hours of such content and want to figure out whether I'm looking at a big hard drive, a multi-drive unit like a Drobo, or an enterprise-level storage system.

First, do not buy an "enterprise-level" storage system (you almost certainly don't need things like hot-swap drives and the same level of support - given the costs)..

I would suggest buying two big drives.. One would be your main drive, another in a USB enclosure, and would be connected daily and mirror the primary system (as a backup)

Drives are incredibly cheap, using the above calculation of ~11 GB/hour, that's only 1.1TB of data (for 100 hours, uncompressed).. and you can buy 2TB drives now..

Drobo, or a machine with a few drives and software RAID is an option, but a single large drive plus backups would be simpler.

Storage is almost a non-issue now, but encode time can still be an issue. Encoding h.264 is very resource-intensive. On a quad-core ~2.5GHz Xeon, I think I got around 60fps encoding standard-def (DVD) to h.264 (compared to around 300fps with mpeg4). I suppose that's only about 50 hours, but it's something worth considering. Also, assuming the HDV is on tapes, it's a 1:1 capture time, so that's 150 hours of straight processing, never mind things like changing tapes, entering metadata, and general delays (sleep) and errors ("opps, wrong tape")

Answer 6

hi,

I'm a friend of keeping the original files, so that you can still use the archived original ones and do new encodes from these fresh ones when the old transcodes are out of date. eg. migrating them from previously transocded mpeg2-hd to mpeg4-hd (and perhaps from mpeg4-hd to its successor in sometime). but all of these should be done from the original. any compression step will followed by a loss of quality. it will need some time to redo this again, but in my opinion it's worth the effort.

so, if you want to keep the originals, you can use the running time in seconds of you tapes times the maximum datarate of hdv (constants 27mbit/s I think) to get your needed storage capacity