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The speed of writing to DVDs is limited mainly by two factors, the speed capability of the writer and the speed rating of the media used. Both these factors have been steadily increasing but your speed is always limited by the lowest one. You might have the latest 16x writer but if the media is only 2x then that's the speed it will write at.
This I understood for the years I've been writing DVDs on the computer but I also write to DVDs from TV using Panasonic DVD recorders. Mostly it will be in real time but as my latest one also has a HD there is the option for High Speed dubbing. I just went to transfer some shows on the HD to a DVD-R using High Speed and it said it would finish in 7 minutes. I let it continue and yes, it did finish in 7 minutes. To make it playable on all DVD players it needs to be finalised and that takes less than one minute so it would take 8 minutes to burn 157 minutes, that's about 20x speed and the media is a cheap one rated at 4x. The disc seems perfectly OK so how can that happen?
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The burner didn't recognize that the media was 4x, or it ignored it.
And that 8 minutes or so is really 16X. The fact that it was 157 minutes of content just means that it was compressed more than if it was 90 minutes of content. The disk will only hold roughly 4.37 gigs of data formatted and finalized. On playback that disk may exhibit errors, or be unplayable in some DVD devices.
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Some media can be written to at a higher speed than their advertised rating.
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You're mistaking the duration of the video for the content in MB.
If it were uncompressed NTSC standard video, the conversion would be easy at roughly 1MB per frame x 30 fps.
But when compressed, there's a big difference. My DVD recorder can record in 6 different compression modes, ranging from fitting 1 hour of video to 8 hours of video on a single sided DVD. Filling a DVD with 8 hours of video should take the same amount of time as filling a DVD with 1 hour of video because what matters is the amount of data written ( 4.3GB ), not the duration of the video.
A 1x DVD burns at 1.32MBps, so at 1x a full 4.3GB disc would burn in about 54 minutes.
A 4x DVD would take roughly 14-15 minutes to burn 4.3GB.
If your disc burnt in 7 minutes then it either was burnt at 8-12x (there's actually not that much difference in burn times between 8x and 12x) OR you only filled about half the disc with your compressed video.
I suggest that you check out the disc on your Mac. Get info on the VIDEO_TS folder in the Finder and if it's around 4GB then the disc was burnt at 8x or 12x.
And if the video takes up much less than 4GB on that disc then you might want to kick up the quality setting on your recorder by a notch or two. Most DVD recorders make the quality-setting look like the speed-setting on a VHS deck with presets like SP/LP/EP/SLP where SP is the highest quality but allows you to fit much less video on the hard drive and SLP is the lowest quality but allows you to fit much more on the hard drive.
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Followup: I just checked and it seems that Panasonic is using 8x burners in their DVD Recorders right now.
A typical EP mode recording might average 64x compression so 157 minutes would take up around 4.2GB.
Given that estimate and the likelihood that there is an 8x burner in that recorder, I'm guessing that you recorded a whole DVD at 8x.
But please check it out on your Mac as I described above. I'd like to know how good my guess was.
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Thanks fellas. A lot of the info I knew already but the extras did explain it more.
On my Panasonic I usually record on the LP setting to give 4 hours on a disc or the equivalent on the HD. This is good enough quality for my wife and myself for everyday time shifting of shows we won't be keeping after watching. Things we might want to keep tend to be recorded at the '2 hr per disc' setting onto the HD and then after editing (top and tailing + ads) they get dubbed to a DVD-R using the FR setting which fits it exactly to the size of the disc at the best quality allowable.
In the last couple of weeks I've been working my way through old videotapes to see about transferring items to DVD. Being video and a few years old the quality is easily captured on the '4 hr per disc' setting with no visible loss although I still do the 2 hour setting at times. This is done to the HD where it is edited and then dubbed to a DVD-R again usually doing the FR method. This dubs at real time speed but this morning I wondered about doing the High Speed Dub which can only be done like for like so a recording on the HD at SP gets transferred at SP. This leaves space on the DVD-R which can be added to up until the time it either runs out or you finalise the disc so it can be played on other machines. That's what I did this morning with 4 shows recorded at the '4 hr per disc ' setting totalling 2hr 37min so I had 1hr 23min left.
That's about 65% capacity. 65% of one hour is 39 minutes which if burnt in 7-8 minutes works out at less than 6x. OK, I got it now. Thank you.
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Your follow up:
I cannot check it out on the Mac yet as I want to add another small show to the disc before finalising it but I'm sure your thoughts are correct.
