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Discussion Starter · #1 ·
Anyone have an approximate conversion chart for equating hard drive size to hours of High Def recording?

Eg, Standard HD sizes = 250gig, 320 gig, 400 gig, 500gig and 750 gig...and how many hours of High-Def they will record?

Thinking about upgrading my TivoHD and debating if I want to wait for the eSATA enabling or if I want o just replace the hard drive.

Any timeframe on the eSATA port enabling for the TivoHD?

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Recording time in HD is fairly easy to calculate, provided you make some kind of assumption as to the bit rate of the content, which will vary from channel to channel. Locally, over-the-air broadcast bit rates seem to vary from about 15 Mbps to 18.5 Mbps and the highest bit rate HD cable channel broadcasts (ESPN, HDNet, TNT, etc) average around 18.5 Mbps. Using 18 Mbps, we get:

18 * 3600 seconds-per-hour = 64800 Mbits-per-hour / 8590 Mbits-per-GB = 7.54 GB-per-hour

Note that that calculation assumes 2-to-the-30th bytes-per-GB, which is how engineers working with computers would think of GB (and what computer software--like TiVo's recording info dialog--means when it gives figures in GB). Marketing people mean 1 billion (10-to-the-9th) bytes when they say GB, so a drive marked 500GB on the package is actually around 465 computing GB (I say "around" because marketers tend to round up :rolleyes: ). In marketing terms, 18 Mbps content consumes 8.1 billion-bytes-per-hour, so a 500GB drive would hold a bit over 61 hours of it.
 

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mikeyts said:
18 * 3600 seconds-per-hour = 64800 Mbits-per-hour / 8590 Mbits-per-GB = 7.54 GB-per-hour
That only accounts for the video and doesn't include stuff like the multiple audio and closed captioning (yes, I know cc isn't that huge). 8 - 9 gb/hour is a better, more conservative estimate.
 

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pkscout said:
That only accounts for the video and doesn't include stuff like the multiple audio and closed captioning (yes, I know cc isn't that huge). 8 - 9 gb/hour is a better, more conservative estimate.
How do you figure? It accounts for the entire stream as recorded.
 

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Discussion Starter · #8 ·
Yes, I'd agree, would be nice if Tivo supported NAS and UPnP...and DiVx (networked, not hosted through TivoDesktop).

I'd agree, HD content is hard to estimate. 480i is significantly different then 1080p/120Hz, but was just going for a general guess/estimate and sounds like 8gig/hour is a reasonable guess.

Thanks!

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