Is DVD authoring a loseless process? + file size question

[kb1985]

Is DVD authoring a loselless process? I mean if I have the source MPEG file, make it into DVD and then rip it again to MPEG will the quality be the same?

And one more thing:
is there any upper file size limit for MPEG files? I know there is 2 GB limit for AVI files.

[yoda313]

Hello,

There is no limit for mpeg files. And I'm not sure if there is a avi file limit anymore. I know the dv stuff can be 10s of gigabytes large.

Yes if you go from mpeg2 to dvd to mpeg2 again there will be no change. VOB is merely a wrapper for the mpeg2 much as avi is a container for different types of codecs.

Kevin

[kb1985]

thx for the reply

[adcvideo]

Hi,

The avi file size limit had to do with older Windows/DOS disk formatting which would not permit any file size to be over 2 GB. Windows XP NTFS has a much higher file size limit.

[Garak128]

With that said. VOB's are still limited to 1gb. And most programs won't accept MPEGS over 2gb... So there are limits. Not really practical to have some ginormous files neways.

[ZippyP.]

And most programs won't accept MPEGS over 2gb...

News to me. I create near DVD size mpeg files (>4 GB) all the time and have no problems.

[dcsos]

MPEG-2 is a LOSSY CODEC, but when you rip and put back files, there is no loss, unless you shrink)

you loose data when you compress a VIDEO signal

DV TAPE can store 2x as much datas as a DVD..when you make a DVD you are compressing the signal and discarding information


There have also been some confused posts about file size limits
VOB's are limited to 1GB by design.
This is so machines with file size limitions like WIN 95, 98 or MAC OS9
can play and make DVD's

those Operating Syatems have a built in limit to 3.99GIGS in any one file, so the 1Gig VOB is well below that

Other systems (PENTIUM ONE or TWO with old bios) have HARD DRIVE size limits

[Cornucopia]

VOB limits are Internal to the DVD spec. If you're ripping via say DVDDecrypter, you can set it to concatenate (merge) the sections to restore the original length of the source MPEG--No Loss/Quality hit.

Have done this a number of times:

1. Simple Digitize w/ Hi Quality DVD recorder (Pioneer PRV-1900 w/ realitime ~VBR), Finalize
2. Rip disc w/ DVDDecrypter in IFO mode, demuxing raw streams
3. Convert AC3 to wave, edit wav w/FX, commentary, remix
4. Make new AC3 from remixed wav
5. Create new DVD w/ m2v, ac3#1,ac3#2, photoshop menus, maybe even subtitles.

Much faster than digitize to computer, edit, encode, etc.
Has worked fine w/ 2-8GB m2v files

Scott

[kb1985]

Maybe I will write what I'm planning to do. I have lots of old c-vhs analog home made tapes which I want to make into DVD's. Unfortunatelly I don't have the DVD Writer but I'm planning to buy it in the future. So what I want to do is to copy all my analogue tapes to digital format using "analog -> digital converter" which is in my Sony DV camera. Unfortunatelly I can't store the videos in the DV format, because I have "only" about 80 GB of free space one one of my hard drive. The space which I probably won't ever use (because I have two other 120 GB HDD's). I hate the feeling that my analogue tapes are constantly losing quality so I want to capture them to DV, then convert to some other format (MPEG2?) and put them on my 80 GB HDD and wait until I have appropriate equipment to burn them on DVD. And the question is is it ok to store each video in 3,9 GB mpeg file or should I split it into smaller parts?

When I will burn them to DVD I'd like them to be easily editable (after riping back on HDD), so that's why I would prefer them to be in one file, but I'm not sure if it is possible because of the files size.

[Cornucopia]

You've got a couple of options here:

1. Pass thru digitize Analog-->DV, Save to DV tape (either direct or after assembling on computer)
2. Buy extra HD's (cheap these days) Digitize, save as DV-AVI files on HD
3. Digitize-->DV, Encode to MPEG2, burn as data DVD's <= 4.3GB filesize limit
4. Same as #3 above, but save to HD (MPEG2 smaller than DV sizes)
5. Leave them on Analog til ready to Digitize-->DV, Encode to MPEG2, Author and burn std DVDVideo

Sounds like you're leaning toward #3 or 4. It's workable, but editing is much more of a pain in MPEG2 than in DV (Interframes, GOPs, lower bitrate, etc). If you're not careful, you'll lose quality each time you edit (on some or all of the file, depending). You're also stuck with whatever quality you choose with it's initial MPEG bitrate--it won't ever get better, even you you're intentions toward that particular clip changes.

#5 you don't seem to want to do, but it's OK if you know you won't be playing using the analog tapes in the meantime, and short-term storage environment is high quality.

Why don't you want to hook up and use those 120GB HD's?

My short/mid-term suggestion is #1. They'll still be tape-based, but it'll be digital and will take MUCH, MUCH longer to wear out. By then, you'll be ready to encode, author and burn.

Scott

[kb1985]

Thx for the reply!
Option 1 sounds interesting, but I think I will decide to use option 4. You say that MPEG2 is not good for editing because of lower bitrate, that's why I would create really big mpeg files. I would like to fit no more than 1 hour of the video on one DVD. My settings are: variable bitrate, max bitrate 9627, average bitrate 8000, minimum bitrate 5000, audio bitrate 256 Kbps mpeg layer 2. Is it fine?

What are other traps of editing MPEG files? Give me some hints and I will try to google for more, but just need some keywords.

[kb1985]

I don't mind the file size as long as it doesn't exceed 4 GB (fat 32, i'm using it because otherwise i have problems with some of my hardware... long story about weird cd-burning problems ).

[Cornucopia]

To edit MPEG2, you'll need:

1. An NLE that understands (reads/decodes) MPEG2
2. It must also either A)Edit on the GOP boundary (~every 15 frames) or B)Edit on the Frame, but smartly re-render/re-encode only those frames in the GOP that are subsequently unreferenced.
3. It must also either A)Save/Remux the GOP-edited file or B)Export a Newly Rendered and Encoded MPEG2

Look to the Tools section for a good selection of apps.

If you are going with #4, keeping the bitrate as High as possible and the GOP length less will help with editability (maybe I-frame only, or I & P frames), but once you get to the stage of DVD authoring, if you don't want to have to re-encode again to get an efficient GOP length, you may want to keep it at the final GOP length. Very High bitrates to a good place to start no matter what. It's always easier to move downhill than up.
Personally, I'd go with 384kbps for audio, but 256 isn't bad.

Realistically and in the long run, you'll have much less problems using NTFS-formatted HD's. If you're having burning problems, it more likely is caused by something else in the mix (hardware conflicts, bottlenecks, background processes, etc).

I have been using NTFS for my main video HD's for 4+ years, no problems. Occasionally have problems with burning CD's from network drives, but what do you expect?

Scott

[kb1985]

Default gop was:
I frames: 12
P frames: 3

I changed it to
I frames: 1
P frames: 1
And now the pattern is: iiiiiiiii

Is that ok? The estimated 1 hour video file size is only 160 MB bigger so I can accept this.

I've downloaded TMPGE because it had some recommendations when i googled and want to cut the file without loosing the quality. Is it possible with that tool? Or maybe you suggest sometihng better? I just need to cut/join files, no expert editing.

[Cornucopia]

Something about your settings isn't quite right.

Most (Open) GOP's default to something like: IBBPBBPBBPBBPBBPBB, which is
I=1, P=5, B=12total (2 to each interval)

and all I-frame GOPs have (by its nature) NO P frames, so the above would change to I=1, P=0, B=0

AND

You get good compression efficiency particularly through the use of the P and B frames. Therefore, I frames are compressor inefficient. That is,

To get good quality with I-frame only footage, it really only makes sense to give it extra high bitrate, say ~8-15Mbps. This will mean you won't be saving much on HD space.
-or-
If you want to save on HD space, you must lower the bitrate. If you lower the bitrate on I-frame GOP MPEG, you'll get bad quality. Therefore, you really want to stick with a standard GOP, and it probably makes sense in your situation to use Closed GOPs, plus you might be able to get away with middle-of-the-road bitrates and I- and P-Frame only GOPs (I=1, P=14, B=0) on some shorter material (but not for most of your stuff).

Re: the MPEG cuts-only editors
Try Cuttermaran or the Womble products. TMPGEnc is workable in a pinch, but the UI isn't right for visual timeline editing. The TMPGEnc MPEG Editor software might be what you need, but it's not freeware.

Scott

[kb1985]

I'm not quite sure what you mean by closed GOP's. So finally you say it is best to use I=1 P=5 B=12 or slightly modified version of it?

[Cornucopia]

Open GOP:

I-B-B-P-B-B-P-B-B-P-B-B-P-B-B-P-B-B-

Closed GOP:

I-B-B-P-B-B-P-B-B-P-B-B-P-B-B-P-

Last 2 B's missing. Why? Remember B = Bi-directional. They reference earlier frames (I & P) and later (I & P). If they're at the end of the GOP, they are actually referencing the I-Frame from the next GOP. That's bad for editing--too complicated to reconstruct quickly and with high quality in an editing/compositing environment. Closed GOPs only reference frames from within its own GOP. Open = more bitrate efficient, Closed = more easily workable/editable/seekable.

Finally, Yes to the last part. (at least in your case)

Scott

[kb1985]

I found one more option that sounds useful. I found an option called "visual content scene detection" which happens to automaticcally change one of the P frames into an I frame when it detects a new scene.

[Cornucopia]

Yes, in your case, it would make sense to make use of that feature. Resets the GOP header, I-Frame, and Sequence Start descriptor at any scene change that is "Noticeable" (above it's threshold algorithm). Would make subsequent editing much easier.

Scott

[kb1985]

I made it into
...BIBP..."

[Cornucopia]

Ok!?

As long as that works for your situation...
(always test and see)

Scott

[kb1985]

Estimated time 4h
Will see tomorrow.

[kb1985]

I don't see the difference really. Maybe my eye is not trained well enough. I hope that "BIBP" is the right choice (hoewer i 've chosen it without any particualr reason.. i just thought that i have 4, 2 GB to use for 60 minutes of video so I have lot of space for additional I frames). If you have any suggestions, please share them.

[Cornucopia]

Test with a small segment--say 2-5 minutes of your source AVI.

Make encodes at a particular bitrate or spread of bitrates (3, 6, and 8.5 Mbps, all CBR), using I-Frame only GOP.
Do the same thing again, only using GOP=[I,P,P,P]
Do the same thing again, only using GOP=[I,B,P,B,P,B,P,B,P]
Do the same thing again, only using GOP=[I,B,B,P,B,B,P,B,B,P,B,B,P]
(These are all closed GOPs, so they should be ok for editing)

Compare
You'll see that the smaller GOP size should have higher bitrate requirements (and concurrent filesize) for a given quality level.
-or, to put it another way-
Smaller GOPs look worse than larger GOPs at the same bitrate.
They're just not as "efficient".

BUT...

They're better to work with for editing.

The GOP sequence examples I gave are fairly common. The one you recently mentioned isn't. I would STRONGLY recommend that you stick to a common GOP sequence for compatibility reasons.

Once your comparison is done you should be able to find a happy medium between editability and filesize/bitrate.

Good luck,

Scott