Beginner encoding question

OpChiasm wrote on 11/15/2005, 4:01 AM

Thanks in advance for any help.

I'm working on an end-of-season presentation for a high school team. Please bear in mind that I am just the Dad of two of the girls on the team - I'm strictly amateur.

The presentation will be output to DVD for projection in a small theater. The DVD will have 8 "chapters", but I've set it up to play continuously from the first chapter on through the end. The "chapters" are individual veg files and range in length from about 2 minutes to about 7 minutes. The "chapters" include photo montages, titles, video footage from games, etc. and are divided into "Roster", "Coaches", "Games", etc.

When I did this last year, everything looked great except the actual game video footage that was recorded with a Sony Digital8 camcorder. I believe the issue is related to the parameters selected for rendering the veg files. I can't remember exactly what I did last year - I think I rendered to avi and let DVD Architect re-render everything.

This year, I was planning on rendering each of the 8 veg files to mpg and ac3 files and dragging those into DVDA.

Finally ... the question. The sum total of all the veg files is about 35 minutes. One of the veg files is composed almost exclusively of the game footage and is about 7 minutes. I was going to select the DVD Architect compliant mpg codec (I forget exactly the template's name) and switch the video setting from "Good" to "Best".

Is this the best option for maximizing the quality of the game video?

Thanks a million.

Comments

Chienworks wrote on 11/15/2005, 4:08 AM

Good vs. Best has almost no impact whatsoever on video footage, so don't worry about it. In the MPEG custom settings windows under Video the important things to note are the Quality slider which should be all the way to the right, and the bitrates, which should probably be around 8,000,000 for max and 6,000,000 for average. Two-pass can help a bit, but it won't make a huge difference.

OpChiasm wrote on 11/15/2005, 4:47 AM

Thank you *very* much.

Will making those changes on about 35 minutes of material affect whether it will fit on a DVD?

Thanks again.

fldave wrote on 11/15/2005, 5:02 AM

35 minutes should definitely fit with those settings. Search the forum for "bitrate calculator" for a link to a tool that many use.

I would recommend checking the "two pass" switch on the video parameters also. It takes a long time, but it can make the best of the encoding quality. As long as you have the time to render it and are not on an immediate deadline, I would use two pass.

riredale wrote on 11/15/2005, 8:06 AM

Here's a simple little calculation to figure out bitrate:

Average total bitrate = 600 / minutes of video

So if you have 35 minutes of video,

Average total bitrate = 600 / 35 = 17Mb/sec.

Note that the DVD spec says the bitrate limit is about 10Mb/sec.

In other words, you can run the MPEG2 encoder wide-open until you get to about 60 minutes of video. After that, you'll have to begin cutting back on the bitrate. At about 2 hours of video, you'll have to encode very carefully with a very good MPEG2 encoder in order to not show any artifacts.

In general, people on this forum have found that burned DVDs work best if the average bitrate is not higher than about 8Mb/sec or so. This gives a DVD player a bit of "breathing room" in case it gets an error on reading and has to go back to re-read a section.

One additional note: the formula above is for the total bitrate. You need to consider that audio is part of that total, so if you encode audio using Dolby Digital (AC-3) at 192Mb/sec, then you subtract .2 from the total bitrate to get the average VIDEO bitrate.

Example: A 90-minute video with 2-channel AC-3 at 192Mb/sec--

600 / 90 = 6.66Mb/sec

6.66 - 0.2 = 6.46Mb/sec for video

So if we encode the video with VBR:
Video min = 0
Video avg = 6.46
Video max = 9

If we encode the video with CBR (definitely not recommended):
Video bitrate = 6.46

OpChiasm wrote on 11/15/2005, 9:28 AM

Thanks very much for all the help.

The banquet isn't until December 6, so I have plenty of time to render.

My plan is to use max =8, ave=6, two pass.

Thanks again.

OpChiasm wrote on 11/15/2005, 11:15 AM

Postscript:

I finally heard back from the "technical person" at the theater. Here's what he said about why the video didn't look so great:

The problem we have with projecting video images is that we are taking a medium design for a TV and running it thru our projectors that are really design for playing high definition media. Our projectors do not work well at this application. The best that I can offer is for them to do a test sample, give it to us and let us see how it plays. Or they can stay away from video footage and use still shots. A DVD of high def quality looks great on our system, video does not look as good and sometimes with these projectors does not play at all.

Anyway ... the video certainly did play last year and was watchable, if not great quality. I hope by implementing the suggestions here, it will be much better than "watchable" this year.

Thanks again.

mark-woollard wrote on 11/15/2005, 12:20 PM

Don't mean to but in here, but with a 35 min production, you could simply use a Constant Bit Rate (CBR) of 8,000,000 thereby getting the best quality plus less render time. Variable (VBR) is only really helpful when your program exceeds about 60 minutes and you want to maximize the bitrate while getting all to "just fit" on the DVD.

I must say the statement that the shool's projectors are designed for HD I find puzzling. There are few native HD projectors out there and they cost an arm and a leg. Sony's Qualia is only around $30,000. Most projectors that schools would purchase are SD resolution and internally convert HD to SD. So if you you're supply decent quality SD material on DVD, it should look fine.

Chienworks wrote on 11/15/2005, 12:38 PM

The other thing i find odd about their statement is the part about "Hi Def resolution images". This doesn't make any sense because once you've put those images into a DVD, no matter how they started out they're now 720x480 (or 720x520 for PAL). They are going to go to the projector at the same resolution as the video.

I'm still betting on it being a bitrate issue. With lower bitrates stills still look ok since there is no movement. Video suffers much greater harm. The artifacts caused by the encoding will be more visible on a huge screen than on a smaller monitor.

Now, on the other hand, it is quite likely that the still images had better color, contrast, sharpness, and focus than the video did. The still images also would not suffer interlacing effects that might be visible in the video when projected.

I think if last year's video was viewed on a computer monitor with sufficient objectivity, the poor quality of the video clips would be noticeable there too. I doubt that the projector is part of the quality problem. The only thing the projector is doing is making the image much larger and therefore making the flaws more noticeable.

OpChiasm wrote on 11/15/2005, 12:58 PM

FWIW ... this isn't a school auditorium. It's Hershey's Chocolate World 3-D Theater. I think it's within the realm of possibility that they have a $30K projector. I know they don't want anyone anywhere near the screen when they let us use it.

johnmeyer wrote on 11/15/2005, 2:13 PM

If their projector can project NTSC video, then your video should look great.

Encode the video in Vegas. Use the NTSC DVD Architect template. Change the average bitrate to 7,000,000 and leave everything else the same. When this is finished, encode the audio using the Stereo AC-3 template. Use the same file name that you used for the video.

Do this same thing for each of your VEG files.

In DVDA, insert a Music Compilation (don't worry, it works great for video). Drop each of your MPEG-2 video files into the Music Compilation. If you used the same file name for the audio for each of your video files, DVDA should match up and find the audio for each clip.

The advantage to using a Music Compilation is that you will get seamless navigation across chapter boundaries. If this isn't important, just put the MPEG-2 files into your project in the normal way.

DVDA should do NO re-encoding of the audio or the video. The video should look pretty much as good as the original DV or Digital8 tapes if you create the project in this way.

OpChiasm wrote on 11/15/2005, 2:27 PM

Thanks very much, john.

I did a test run over the weekend (using the DVDA NTSC template) and added the mpg files to DVDA. I set the end action for each of the mpg's to the next mpg and that seemed to work pretty well. I need the DVD to run straight through for the banquet, but plan on giving each of the seniors a copy of the DVD as part of the senior gift. For that, I wanted the ability to select chapters. I have 2 seconds of black silence at the beginning of each "chapter" to further emphasize that they are distinct "themes", if you will. For this purpose, seemlessness is not too important.

Now, I'm going to go back and re-render the video of all my veg files according to the suggestions I got here. It'll be awesome.

I can't thank everyone enough for their help.

johnmeyer wrote on 11/15/2005, 5:59 PM

Good luck with the project. I did a senior video last year and we gave it away to 160 graduates. The whole thing got away from me, and I ended up with several thousand stills, hours of video, and lots more, which I cut down to 12 music videos, plus "bonus material." Hopefully your class will enjoy it more than mine. I got exactly one thank you, from a parent. No one else made a single comment. Oh well, I thought it was good (he said modestly), so at least I have satisfaction from that.

OpChiasm wrote on 11/16/2005, 3:41 AM

john,

This is for the high school field hockey team, not an entire class. The overall level of interest is probably much higher for me. Although, having watched some of these kids play this year, it's not 100%.

The project is also an order of magnitude smaller than yours. I have 3 games' worth of video (about 3 hours) and a few hundred stills. I did it last year and they were blown away - this is a crowd that's used to never-ending powerpoint presentations at sports banquets. I learned a lot since last year and I'm pretty excited about this year's edition.

Thanks again.