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Useage of Space on Blu-ray Disc
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Gregorian Chanter [Avatar]
Newbie Private Message Joined: Dec 26, 2015 19:01 Messages: 6 Offline
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Yesterday I edited a TV program that I had recorded in its broadcast format of MPEG-2. The result is 90 minutes of edited video.

I burned the edited video on to a Blu-ray disc in MPEG-2 format using PowerProducer 5.5.

I checked some of the Blu-ray disc space usage figures. Here is where things get interesting:

Blank disc space indicated by PowerProducer: 24.2 Gb

Blank disc space indicated by Windows File Explorer: 24.6 Gb

Space needed to record video as indicated by PowerProducer: 20.4 Gb

Actual space use as indicated by Windows File Explorer: 13.2 Gb

I am not going to quibble about the slight difference in blank disc space between PowerProducer and Windows.

But I do have a problem with the actual disc space usage. PowerProducer said it needed to use 84% of the disc space. Windows shows that 53% of the disc space was used. I can see how much of the blank space was burned on the disc, and I say that Windows has it right, and PowerProducer has it wrong. This means that PowerProducer overestimates the amount of disc space needed by more than 50%. PowerProducer will not attempt to burn a disc if its space estimate shows that there is too much video to fit on a disc. This means that (best case!) I am forced to waste over 1/3 of the space on a Blu-ray disc.

I would be overjoyed if there were an option: "The video may not fit on the disc. Attempt to burn anyway? [Yes] [No].

I have some re-recordable Blu-ray discs that I can use to give it a try. But PowerProducer will not let me even try.

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TonyL [Avatar]
Newbie Private Message Location: Nr. Coventry, UK Joined: Oct 10, 2015 04:07 Messages: 46 Offline
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I also found it strange how PD14 reported on 'Used disc space'.

I recently, for the first time, went to use PD14 to create a dvd but was put off by PD14 showing a very high disc usage so I switched to Sony DVD Architect and made my dvd using the same files.

PD14 had stated the 'Used disc space' to be 18091MB, which will not fit on a DVD or BluRay.

I wondered if PD14 gave a high usage because it needed to re-render/encode the files.

Seeing this post today I carried out a few simple tests with PD14 and three files individually.

I took an MPEG2-PS file, call it 'A', that in Explorer had a file size of 1925.7MB, and dragged it into PD14's Create Disc. There it had a 'Used disc space' of 4397MB, i.e. more than twice that of Explorer. Why??

I then ran file 'A' through Total Video Converter to 'convert' it to an MPEG2 (audio for both is AC3 @ 128Kbps). Explorer file size of 929.5MB. PD14 'Used disc space' of 4397MB, i.e., nearly five times that of Explorer. Why??

Note that the 'Used disc space' is the same for both files.

Next I used PD14 to 'Produce' file 'A' as an MPEG-2 DVD HQ 720x480/60i (8Mbps). Explorer file size of 3,144MB. PD14 'Used disc space' of 3882MB. Ahh! These two readings are closer together.

I then used GSpot to look at the three files and this gave me the answer - which frankly I should have realised sooner as it gets a mention quite frequently on video/dvd sites.

GSpot gives the 'average bitrate' of the video stream as:

File A = 2503kbps

TVC output file = 1997kbps

PD14 output file = 6875kbps

Hence, the higher the bitrate the larger the file.

PD is only doing what it's set to do. The default 2D Disc setting for DVD Video is MPEG-2 HQ - Best Quality, thus the stated 'Used disc space' of 18091MB (not able to fit on a DL DVD). Choosing 'Smart fit' instead of HQ Best Qual., produced a warning and only reduced the 'Used disc space' to 10541MB.

So if I only had PD14 and didn't know better I would not have been able to create one DVD with my original two files on it. But I did know better and used DVD Architect. As a new user of PD14 I'd be interested to know if I could have done it in PD14.

TonyL

This message was edited 3 times. Last update was at Jan 01. 2016 10:48

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Gregorian Chanter [Avatar]
Newbie Private Message Joined: Dec 26, 2015 19:01 Messages: 6 Offline
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TonyL-

I cannot comment directly on what you are seeing, but I think I can throw some light on the issue.

I have looked at the size of the MPEG-2 files from recording standard def broadcast TV. For the same amount time recorded, the MPEG-2 files are much smaller than the file sizes that I see when I use a DVD recorder, or the resulting files when I make DVDs using some non-Cyberlink software. Using this other software, the recorded video file (VOB) is about 2.3 times larger than the MPEG-2 source file.

I don't know this, but my guess is that DVD uses redundancy in the recording so that essentially everything is recorded twice. Add some necessary overhead, and the result is a file 2.3 time larger than the original source material. The advantage is that localized damage on the disc would not prevent playback of the recording.
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