FR burn not filling the DVD ?

bomber1978

Standard Member
Hello,

I'm using the Australian Panasonic DMR BWT 700 GL Recorder...
I recorded a TV programme in DR mode, I edited out the TV commercials and it's final length on my DVD Recorder is 43 minutes...
Then I burned it to DVD-R (4.7GB) using FR mode as FR mode is supposed to use up as much disc space as possible from what I thought I understood?, however I have saved the 4.7 GB DVD-R to my computer HD to make a copy for someone, and I noticed the size of the file on my computer HD is only 2.84 GB, as I used FR mode to burn the DR recording to the DVD-R shouldn't it have used up as close to 4.7 GB as possible, rather than just 2.84 GB?
*It seems to be a lot of space not used.........

So I checked out a couple of other discs, I have a programme on my DVD Recorder recorded in DR mode which is 3hours:18minutes, I burned that to a 4.7 GB DVD-R in FR mode and ripped to my computer, the size on my computer HD is 4.02 GB, I also burned the same 3hours:18min DR recorded programme from my DVD Recorder to a dual layer 8.5 GB DVD-RDL using FR mode and ripped to my computer HD is 7.61 GB.

Is this normal?, isn't the purpose of burning to DVD-R in FR mode to fill up as much of the discs space as possible?
Shouldn't 43minutes of DR recording fill up much more than just 2.84GB of a 4.7GB DVD-R?

Thanks
 

LV426

Administrator
Staff member
To fall within the specification for DVD-Video there is a maximum data rate which cannot be exceeded, and that equates to around an hour's play time on a 4.7gb disc. Encoding your 43 minute footage up to the maximum permitted data rate would never fill a disc.

As for your other examples, whilst I'm not sure,
- first, DVD-Video encodes are done at a varibale data rate depending on the demands of the footage
- second, in order to be able to encode footage arriving at the machine from an AV input (for example), the onboard encoder HAS to work realtime, discovering what's actually in the footage as it goes.
- third, no such machine has two encoders, so all encoding is done as above, even if it's already on the Hard Drive.
- I'd guess then that as the complexity of the encode (amount of movement etc., in the image) can't be predicted without running two "passes" (something your PC might do, but which table-top machines don't) the precise data rate needed to exactly fill a disc can't be predicted.
- so some upfront estimate has to be made; and that estimate would have to assume a worst case - a very data demanding encode throughout.
- It is of course quite likely that as the recorder does the encode, it finds parts of the footage that don't demand as much data as others.
- Sensibly, it reduces the data rate for these so as to allow a worst case for what follows (footage it hasn't yet seen or evaluated)
- Hence you always have some spare data space. Practically unavoidable.

The only resolution here is for a two-pass encode; where the entire footage is evaluated for complexity first, and the appropriate data rate established before the true encode. Which takes twice as long, and, as I say, is a feature found in Computer programs (and not table-top encoders which HAVE to be able to operate real-time).
 

bomber1978

Standard Member
Thanks, so I'm wondering then, if I plan on putting 50-60 minutes onto a standard 4.7 GB DVD-R, which is going to result in a better quality DVD-R, a programme recorded in DR mode burned to disc in FR mode?, or is it better to record the programme in SP mode and high speed (lossless) burn to disc? (I'm basing that on thinking 1 hour of SP mode will just squeeze onto a 4.7 GB disc won't it?).
Thanks
 

LV426

Administrator
Staff member
SP mode represents around 2 hours on a DVD single layer (so, a reduced data rate). Your recorder should have the option of a "better" rate. My UK spec Panasonic calls this XP mode. There is a table in my manual listing these terms (XP, SP, LP, EP) and the duration that fits to various disc types. So, for one hour, you should use XP for max data and max quality.

In fact, the trick is to encode only once if possible, and it doesn't matter if that's done as you do the initial record onto the HDD or at the time of disc burning. High Speed copy to disc does not encode; it merely copies the data into the DVD-Video file structure. And an initial DR mode record onto the HDD does not encode, either; just places the incoming digital stream onto the HDD.

So, an initial encoded record to HDD followed by a High Speed copy to disc is one encode; and an initial DR record followed by a real-time copy to disc is also one encode. A long way round of saying, no difference as long as the end data rate is the same.
 

Gavtech

Administrator
Thanks, so I'm wondering then, if I plan on putting 50-60 minutes onto a standard 4.7 GB DVD-R, which is going to result in a better quality DVD-R, a programme recorded in DR mode burned to disc in FR mode?, or is it better to record the programme in SP mode and high speed (lossless) burn to disc? (I'm basing that on thinking 1 hour of SP mode will just squeeze onto a 4.7 GB disc won't it?).
Thanks

The better result would come from FR mode in this case, because with no effective space constraint you are effectively encoding at XP mode.

To simplify, FR mode will give you the greatest and best possible benefit in all circumstances.

(Cross posted with LV426)
 

bomber1978

Standard Member
Thanks LV426, sorry I should have said XP instead of SP, don't know why I wrote SP both times, yeah true about only encoding once, I always stick by that rule...
Thanks Gavtech for confirming it's ALWAYS best to record in DR and burn in FR - it's the way I've always done it...
This has answered 2 questions in one really, as I've always wondered what happens if you had for example 45minutes of DR recording and burned it to a dual layer 8GB DVD-RDL in FR mode, but your answer suggests it would be just as high quality as it would if you recorded in XP and high speed (lossless) burned the 45mins of XP onto a dual layer 8GB DVD-RDL....
Thanks
 

LV426

Administrator
Staff member
For 45 minutes duration, there is nothing to be gained by using a dual-layer blank. The FR encode will be at XP mode (maximum rate for DVD-video) which neatly fills a single layer disc for 60 minutes. 45 minutes won't fill a 4.7gb disc, nor will it be any larger (better) on a dual-layer disc.
 

bomber1978

Standard Member
For 45 minutes duration, there is nothing to be gained by using a dual-layer blank. The FR encode will be at XP mode (maximum rate for DVD-video) which neatly fills a single layer disc for 60 minutes. 45 minutes won't fill a 4.7gb disc, nor will it be any larger (better) on a dual-layer disc.

Hi,
Yeah I know 45mins won't fill an 8GB DVD-RDL, it won't even fill a 4GB DVD-R, that's why I was wondering what would actually happen if you burned 45 mins of DR onto an 8GB disc using FR..., I was wondering if it could possibly be better than a high speed XP burn..., but I understand now it would just be the same..., so I understand clearly as Gavtech says, and as I always thought and have used, it's ALWAYS best to record in DR and burn to disc in FR... (obviously though high speed XP burn will save you some burning time!)
Thanks
 
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