Rendering, VOBs and SD DVDs - fun stuff

[Macadoon]

Hi all, stay with me for a moment while I outline my query.
When I go to the local DVD store and hire a recent-release DVD (std def) it plays in really very good quality on my standard DVD player (which doesn't support HD or Blue-Ray). I'd love to be able to produce a DVD image that clear (or close to) myself...
Before anyone points me to other threads ... I have read these already and feel that my questions (below) are not answered in these.
I shoot on a Sony HDRSR1, and use Ulead 11.5 for editing. I use what I think are the correct project settings (below), and always choose the highest output settings, but the the quality of the footage on the DVD is noticably worse than a straight MPEG2 file output. Whilst I appreciate that I am not burning to a DVD that supports higher definitions (and that there will be some loss of quality from 1440x1080i footage), I am convinced the software (or something I am doing with it) is removing more quality than it needs to in the rendering/conversion to VOB phases of the project. I personally think it could be the conversion to VOB that is creating the problem, as when I output to MPEG the quality is excellent. I'm also sure that the output settings are the same as the project settings. If I output to MPEG the quality is excellent

Here's the project properties that I use:
PAL (25 fps)
MPEG files
24 bits, 1440 x 1080, 25 fps
Upper Field First
(MPEG-2), 16:9
Video data rate: Variable (Max. 15000 kbps)
Audio data rate: 224 kbps
MPEG audio layer 2, 48 KHz, Stereo

Could this simply be a bitrate issue? Are there other settings at play than can be tweaked? Should I set the project properties at DVD/Pal 720x576, which I would then replicate in the SHARE option of VS11.5? Are Ulead's rendering/VOB solutions problematic?
Basically, how can I screw the best quality std-def DVD image out of Ulead 11.5?
Your thoughts etc are most welcome.
Andy M

[Ken Berry]

Welcome to the forums!

I am (sort of) assuming you realise that your camera films in high definition mpeg-4 though it uses 5.1 Dolby audio rather than the mpeg layer 2 dual channel you have specified in your project properties.

Standard definition DVDs (your VOBs) are mpeg-2 as you specify in your project properties. So at some stage -- again as I think you realise -- the original high def mpeg-4 has to be down-converted to standard definition mpeg-2. That can take place either as a stand-alone step in the editing module (Share > Create Video File > DVD [or mpeg-2]) or as part of the burning process. I am again assuming that the latter is what you are doing.

Now you don't give us any details of your computer system, so we have no real idea what we are dealing with. But again I imagine (assuming yet again! ) you also realise that your AVCHD mpeg-4 is one of the most demanding of computer resources and so your computer needs to be at least a core two duo to be able to play it smoothly. You can however edit it in that original format if you have a P4 3.0 GHz with hyperthreading, as long as you use SmartProxy.

Now, I realise you are only intending to downconvert to standard definition. And assuming (for the fourth time! ) that by "If I output to mpeg the quality is excellent", you mean outputting to mpeg-2 in the Editing module. Well, if the result is excellent, use that mpeg-2 in the burning module. Otherwise, if you have your original video in the editing timeline, do your edits, and then jump immediately to the burning module (Share > Create Disc > DVD), the *project* .vsp file is inserted into the burning module and NOT the original video. And the properties the program will use to burn the final disc are to be found in the middle of the three icons in the bottom left of the burning screen. That may be the primary reason for lower output quality.

You can change those properties if they are too low quality, but for a standard definition DVD, it is advisable to use no more than 8000 kbps as the bitrate since most stand-alone DVD players have difficulty with bitrates above that... Mpeg layer 2 or Dolby (dual channel or the original 5.1) audio are fine.

But if the bitrate is considerably lower than that (as it would, for instance, have to be if your project is longer than one hour -- it would have to be, for example, around 6000 kbps if the project is around 90 minutes, or as low as 4000 kbps if the project is 2 hours in length), then that will automatically lower the final quality of the video on your DVD.

In addition to that, though, if you are inserting your project file in the burning module, it is still linked to AVCHD mpeg-4 files, and they have to be converted to the the SD DVD-compatible mpeg-2 during the burning process. From experience, this is usually asking for trouble -- again if your computer is not a particularly powerful one. The burning process is complicated enough in its own right, without having to worry about it also having to do the verrrry complex process of converting from the demanding high def mpeg-4 to SD mpeg-2.

So instead, do your computer a favour and, keeping it simple: do your edits, and produce your mpeg-2 of the project in the Editing module. And after you produce your new mpeg-2, you go to File > New Project. Don't worry about giving your new project a name. The objective is just to clear the timeline of your current project.

Once that is done, you select Share > Create Disc > DVD. The burning module will open. Use the Add Media button at the top to insert your new mpeg-2 in the burning timeline. Then go to the middle of the three icons in the bottom left of the burning screen. There is a little box beside the words 'Do not convert compliant mpeg files'. Make sure that box is ticked (it usually is by default). That way, your already compliant mpeg file will not be re-encoded. Then build your menus and burn.

But the basic lesson of all this is, of course, that SD mpeg-2 is NEVER going to give as good a quality as your original HD video, whether AVCHD or HDV. Nevertheless, using high quality (i.e. high bitrate up to 8000 kbps) settings, the quality shown from your SD DVD should still be very good.

However, comparing home made DVDs to commercial ones is also going to be a little bit like comparing apples and oranges. Those DVDs are produced from studio quality movies, and processed through equipment costing hundreds of thousands of dollars, with multi-pass encoding which ensures the absolute highest quality imaginable. You are never going to emulate that with consumer level software which at most allows two pass encoding. For most home made DVDs, nevertheless, the end quality should still be roughly comparable.

However, I would add another caveat from personal experience. If you are showing your home made SD DVDs on a large screen HDTV, then the differences in quality between them and commercial DVDs will be greatly magnified. Believe me -- I know. I used to be exceedingly pleased with the quality of my SD home made DVDs played on my 32 inch CRT TV and could not tell any real difference between their quality and commercial DVDs. But since I bought a 46 inch HDTV, I can barely watch my 'old' SD home made DVDs on it. My only solution has been to buy a 32 inch HDTV and set that up in a separate room with a standard definition DVD player attached via HDMI. The smaller screen is much more forgiving!!

[Macadoon]

Hi Ken,
Thanks for your reply.
Sorry u had to make all those assumptions ... but I'll learn!
My PC is an Advent T9508, with an Intel Core2 Due E4500 at 2.20Ghz. It's running a GeForce7300LE graphics card and has 2 gigs of Ram. I've not experienced any problems with editing AVCHD... so far... although I was mulling upgrading to 4 gig of Ram earlier today!
I wasn't aware my camera recorded in MPEG-4, or of the Dolby 5.1
Thanks.
Presumably, this means that I can downconvert to HDV 720p (for HDV) or HDV 1080i (for HDV) for subsequent editing? I believe these are both MPEG-2 formats? What would your recommendation for the downconverted file format be for optimal dvd production?
Out of interest, for downcoverting AVCHD to MPEG2... what would you suggest for the project properties:
PAL (25 fps)
MPEG files (if I choose this, the audio automatically switches to MPEG audio layer 2, whereas DVD PAL gives me the Dolby sound choice with a 720x576 screen)
24 bits, 1440 x 1080, 25 fps
Upper Field First
(MPEG-2), 16:9
Video data rate: Variable (Max. 15000 kbps)
Audio data rate: 224 kbps
MPEG audio layer 2, 48 KHz, Stereo
Best
Andy M

[Ken Berry]

Well, you computer is certainly OK for editing AVCHD. But while there might be some advantages in converting it to HDV (and I would stick to 1080i rather than move into the often problematic 720p format). But primarily it is a misconception to call that 'down-converting. HDV, particularly in the 1080i format, is arguably higher quality than your AVCHD. Its bitrate, for one thing, is 25 Mbps (as compared to your 15 Mbps -- though again it's a bit like apples and oranges to make such a sweeping statement -- the alogrithms in both formats are quite different...) But anyway, that's semantics.

If you had a less powerful computer, then converting the AVCHD to HDV would make some sense, even if you intended to output to AVCHD hybrid disc or Blu-Ray (the latter can accept either AVCHD or HDV, the former, as its name implies, only AVCHD). But the basic problem even there is that mpeg of any stripe by its very nature (and compression) is a lossy format. Every conversion throws away some of the original data, and thus the quality lowers. With high def video, the process is probably not really noticeable to the human eye after only one or two conversions, but it is nonetheless there.

So, you start out with AVCHD and want SD mpeg-2 for burning to SD DVD i.e. HD mpeg-4 > SD mpeg-2. But you are talking about adding an extra step to this: HD mpeg-4 > HD HDV/mpeg-2 > SD mpeg-2. So that is two generations of conversion and two generations of quality loss. Reduce the loss by having only the one conversion straight from AVCHD to SD mpeg-2 in the Editing module as I suggested, using the properties I have already suggested. Use Share > Create Video File > DVD if your project is an hour or so or less. That will definitely guarantee the resulting is DVD-compliant, and allow you -- as you have found -- to use your original 5.1 Dolby audio. But the highest advisable bitrate is 8000 kbps which will allow an hour (or 70 minutes with the Dolby or mpeg layer 2 audio) on a single layer DVD...

As for the project properties, to a large extent (sacrilege! sacrilege!) they are irrelevant. They don't make any difference to the final outcome unless you choose Share > Create Video File > Same As Project Properties. If you choose Share > Create Video File > DVD, as I have suggested those are all the properties that matter. If your project is longer than, say, 70 minutes, you would need to choose Share > Create Video File > Custom, and use essentially the same properties except that you would need to drop the bitrate to around 6000 kbps if the project is around 90 minutes, or 4000 if it is around 2 hours...

[Macadoon]

Hi Ken,
Thanks for your replies. I'll give them a go today.
Best
Andy M

[Ken Berry]

And let us know how it goes!

[Macadoon]

And let us know how it goes!

Well, after an afternoon of burning and testing ... I can say that your advice has added a dimension of quality to my films that I have hitherto not been able to get.
I ran a couple of films off.
Film One: 30 seconds at 8000 kbps with a single pass, and again at 9800 kbps with double pass
Film Two: 19 minutes at at 8000 kbps with a single pass, and again at 9800 kbps with double pass
I much prefer the end product with double pass encoding and 9800 kbps bitrate, for reasons you have already explained above. Fortunately, my dvd player handles the higher bitrate, but I will use the lower specs for my 'mass produced' dvds for family and friends.
Excellent! I would add that because I spent ages sorting out the lighting before filming, this probably also helped the end quality... but the devil is in the detail!
Andy M

[Ken Berry]

... but the devil is in the detail!

But I am glad it has worked out for you!