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Old 03-10-2012, 01:08
Sideburns57
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I have had some discs for a year so it it about time I use them. Am I right in thinking they can record 9 hours of HD? I heard somethng about restrictions -recording once to Blue Ray or something. As you can tell I am somewhat lacking in knowledge......could someone possibly fill me in on dos and donts please. Cheers.
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Old 03-10-2012, 07:51
mac2708
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Don't know how up to date this is, but it may answer some questions
http://www.blu-ray.com/faq/


1.6 How much video can you fit on a Blu-ray disc?

Over 9 hours of high-definition (HD) video on a 50GB disc.
About 23 hours of standard-definition (SD) video on a 50GB disc.
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Old 03-10-2012, 09:06
Sideburns57
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Thanks for your help
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Old 03-10-2012, 10:26
grahamlthompson
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I have had some discs for a year so it it about time I use them. Am I right in thinking they can record 9 hours of HD? I heard somethng about restrictions -recording once to Blue Ray or something. As you can tell I am somewhat lacking in knowledge......could someone possibly fill me in on dos and donts please. Cheers.
There is no answer to this it depends on what you mean by HD. (ie what the source is)

The file size is determined by the bit rate used.

Blu-ray blanks are 25GB storage (double for the expensive dual layer blanks).

Take Avatar in normal 1D it takes about 35GB of storage for the movie. (1920 x 1080 24fps) Without compression (reducing the bitrate) it won't fit on a 25GB blu-ray blank.

Some typical HD camcorder recording standards

1440 x 1080 interlaced 25fps - Average bitrate 12Mbps

Divide by 8000 to get Gigabytes/second = 0.0015

35GB will hold about 6 hrs

1920 x 1080 interlaced 25fps 17Mbps about 4hrs

1920 x 1080 progressive 50 fps 28Mbps about 2.5Hrs

BBC1-HD recorded content is about 4.7GB/hr so 25GB will hold about 5hrs.

A 45mins recording from BBC1-HD will fit on a single layer DVD blank in HD using AVCHD recording format.

No idea where the above numbers came from, they would seem to be based on interlaced 1920 x 1080 footage from a HD camcorder.

Just look at the file sizes you want to use on a PC.
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Old 03-10-2012, 13:56
Sideburns57
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Wow, you know your stuff!

By HD I mean a direct recording from stored stuff on my Sky plus box to the Blu Ray disc I am sticking in my Panasonic Blu Ray recorder.
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Old 03-10-2012, 14:01
fmradiotuner1
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I don't think these would work with a Sky box unless recording stuff in SD?.
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Old 03-10-2012, 14:02
grahamlthompson
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Wow, you know your stuff!

By HD I mean a direct recording from stored stuff on my Sky plus box to the Blu Ray disc I am sticking in my Panasonic Blu Ray recorder.
So you are intending to record in SD to a blu-ray blank.

Expensive storage compared to a DVD, a little less than 25GB (4 single layer DVD blanks) will cost around 64p.

Blu-ray only really makes sense if you want to record High Definition content.
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Old 03-10-2012, 14:24
Sideburns57
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But isn't the quality better via Blu Ray?
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Old 03-10-2012, 14:45
grahamlthompson
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But isn't the quality better via Blu Ray?
No, why would it be ?. The quality is limited by the source, in this case assuming you are using the best output from the Sky box RGB at 720 x 576.

On your Sky box HDD is an exact copy of the original broadcast.

Mpeg2 compressed if SD, H264/AVC if HD.

The sky box has to decompress to analogue video and audio and downscale to SD if HD (from 1920 x 1080 to 720 x 576).

Your DVD/Blu-ray has then got to

Reconvert the analogue back to digital (ADC - Analogue Digital Conversion) and then re-compress, if you use mpeg4 it will make the file smaller than mpeg2 but it won't make the pictures any better. You can't replace the data lost in the multiple conversions.
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Old 03-10-2012, 19:40
chrisjr
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But isn't the quality better via Blu Ray?
It might be if there was any way to get HD recordings off the Sky box into the recorder. But there isn't. You can only record in SD even if the programme you are copying is in HD.

So you are probably not going to notice much if any difference between recording to Blu-Ray or DVD.
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Old 03-10-2012, 23:17
Sideburns57
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OK, thanks. So it is a capacity thing with Blu Ray discs only. Ta.
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Old 03-10-2012, 23:47
chrisjr
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OK, thanks. So it is a capacity thing with Blu Ray discs only. Ta.
There is more to it than that.

But the big problem with Blu-Ray recorders is the inability to record in full HD from an external full HD source, eg a Sky, Freesat or Freeview HD box or another Blu-Ray player. The only HD source they can record from is their built in tuner(s).

So given that you can't record a Sky HD programme to Blu-Ray in true HD is there any point recording to Blu-Ray apart from the capacity issue? I doubt you'd see a vast difference in quality over recording to DVD.
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Old 03-10-2012, 23:57
Sideburns57
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OK, thanks. The good thing is that I could probably get 4 football games on a single Blu Ray disc, but other than that.......!
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Old 04-10-2012, 00:04
webbie
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I think the Panny blu-ray recrders were pretty close to being mis-sold. DVD recorders plug into sky and you get almost identical copies from your sky sd channels. Why wouldn't people think that they could use a blu-ray recorder in a similar way and get hd copies? I bet it wasn't explained at the point of purchase. It makes these machines pretty crippled.
In this day and age we really ought to have one with an hdmi input. We have been recording off the tv for thirty-odd years now! I know it won't happen but I think it's ridiculous. Just makes people download more....
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Old 04-10-2012, 09:45
chrisjr
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There is no technical reason why an HDMI input could not be provided. Or even several. The problem is HDCP copy protection. The copyright holders insist on it being used so even if it were possible to connect a Sky box or whatever to a recorder digitally the HDCP would kick in and prevent the recorder doing anything.

So why bother fitting a socket that is pretty much rendered useless?
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