[Beowulf] HDTV video file sizes

[laytonjb at charter.net]

Uncle, Uncle!!!

Actually that was  a good answer. I see that I need to learn more :)

So about 8-9 GB/hour....

What I have in mind is a large number of hours of HDTV being recorded to
storage.  I'm guessing that total number of hours, but I think the general
number is over 4,000 hours (about 36,000 GB or 3.6 TB). Actually it's not
that much data is it? Just a few hard drives and you've got it.

Thanks!

Jeff

> At 08:49 AM 5/29/2007, laytonjb at charter.net wrote:
> >Good morning,
> >
> >I was doing some thinking over the weekend (while cooking ribs on 
> >the grill :)  ).
> >Does anyone know who much data 1 hr. of HDTV produces? Let's try 720 for
> >now and perhaps 1080. I'm looking for the file size if you store the 
> >whole thing
> >in a single file.
> 
> 
> Are you asking about "as generated in the studio" or "as recorded" or 
> "as broadcast"
> 
> the raw data rate is >1 Gbps (142.18 Mb/s for NSTC sampled at 14.318 
> Ms/s up to 1.486 Gbps for SMTPE 292M sampled at 74.25 Ms/s)
> 
> 
> 
> There's several compression/redundancy removal steps in the chain, 
> and different HD broadcast media (over the air in US (ATSC), over the 
> air in Europe (DVB-T), direct broadcast satellite (DVB-S, and others) 
> , cable) use different bit rates, and different compression 
> schemes.  And, of course, the DVD (including the new BluRay and 
> HD-DVD) have their own encodings as well.
> 
> In the US, HD is broadcast over the air in a 6MHz wide channel at 
> between 19-20 Mbps (3 bits/symbol).  However, that 20 Mbps stream can 
> be divvied up in lots of ways: 1 really HD channel, 5 SD channels, 2 
> SD channels plus a medium rate HD channel.
> 
> Wikipedia has a lot of info on this..
> 
> The appearance of the decoded output depends a LOT on how good the 
> encoding was.  You can cheap out and just do simple frame encoding, 
> with no frame-to-frame encoding, in which case you get high 
> resolution with lots of artifacts. Or, you can spend a lot more 
> effort on the encoding, and make use of the frame to frame 
> redundancy, and get a lot less artifacts.  The telling difference is 
> if you have something like a panning shot over a complex, but fixed, 
> background (e.g. a forest in the distance).  A good encoder will be 
> able to make use of the fact that big swaths of the image are 
> actually the same from frame to frame, just displaced.  A cheap 
> encoder will not.
> 
> Cable TV and direct broadcast satellite use somewhat different data 
> rates (since they have different heritage), and different encodings, sometimes.
> 
> Compressed digital video that is intended for further editing is also 
> compressed differently, because the "broadcast" compressions tend to 
> have unsuitable artifacts in the editing process. Squeezing a raw 
> data rate of >1 Gbps down into 20 Mbps or so always entails some 
> compromises, and the broadcast compressions are designed to allow 
> inexpensive decoders (and expensive encoders..you'll be making 
> millions of decoders and dozens of encoders) and for artifacts that 
> are visually unobjectionable to an end user.
> 
> As you can imagine, there is much opportuntity for transcoding artifacts.
> 
> These days, H.264/AVC is probably the leading candidate for compression
> 
> 
> So.. for over the air HD broadcasts, 20 Mbps should do you, which is 
> well within the range of a variety of hard disks.   Converting to 
> GB/hr, I get 8-9 GB/hr
> 
> 
> James Lux, P.E.
> Spacecraft Radio Frequency Subsystems Group
> Flight Communications Systems Section
> Jet Propulsion Laboratory, Mail Stop 161-213
> 4800 Oak Grove Drive
> Pasadena CA 91109
> tel: (818)354-2075
> fax: (818)393-6875 
> 
>