Five miscellaneous and newbie-ish questions

[etink]

Feel free to move my post to the newbie or ffmpegx forums, if one of those would be more appropriate.

Hello, all. I'm new to the world of video conversion and DVD burning, and I have lots of questions I would like answered. I've spent at least 8 hours over the past couple of days reading through every guide, forum post and software manual I can find. I should state right off the bat that I'm working on a single generation old Powerbook G4 (1.25 GHz). Otherwise, http://www.doom9.org/ would probably have most, if not all, of my answers.

Next, I'll describe the sorts of files I'll be working on. I'm primarily interested in burning lots of AVIs to DVD. These AVIs will be in many different formats (3ivx, DivX and XVid, primarily), and be of variying resolutions and quality levels, eg music videos or TV episodes or short home-made animations. I have ffmpegx, Toast 6, Sizzle, DivX Doctor II and iDVD/iMovie (most recent versions of each program) available. I'm willing and able to acquire any free- or (cheap) payware for either OS X specifically or UNIX in general. I have a small Linux background and I'm also comfortable with the command line.

There's a LOT of material available online, much of it contradictory. Some of these questions have already been answered in part even on these forums, but oftentimes conflicting information is present in different threads discussing the same problems. So feel free to link me to the definitive "right" answer whenever there is one.

1) What are the pros and cons of Toast vs Sizzle? Which one is most applicable to my situation? So far, I've been using ffmpegx to convert AVIs to mpeg2s. I deselect the Author DVD option, as I want to put several (generally between four and twenty) AVIs on the same disc. Should I then create my DVD image in Sizzle and burn it in Toast, or work directly in Toast? When is each approach appropriate? Should I ever use iDVD for this type of task instead? I've read that Toast can also perform decoding duties. When is this desirable? How does it compare to ffmpegx?

2) Should I be using mpeg2works instead of ffmpegx? Why or why not? I've seen it mentioned in a small number of places, but I don't know too much about it. Is there any other piece of software which is superior to ffmpegx for AVI to mpeg2 conversion (such as whatever conversion features Toast possesses, as mentioned above)?

3) Resolutions. My video files will have many different resolutions. If I have a file in 4:3 or 16:9 aspect ratio, I assume there's no problem. But what do I do when the file has a different ratio? For example, I've got a set of AVIs at a resolution of 512x368, which is a ratio of approximately 1.4 (as opposed to 1.33 with 4:3 or 1.77 with 16:9). This is a set of TV episodes. Naturally, I want them to look good when played in a standalone player. I'd expect my options include cropping, stretching and letterboxing. What should I do, and how do I do it? Further, what's the different between full- and half-DVD resolutions? I was under the impression that TVs are 640x480 (or something similar. I don't feel like Googling up the exact figure, because it's irrelevant). But full DVD is sized at 480x480 and half-DVD is sized at 352x480. Basically, I don't understand what's going on here. A link to a good introductory text be appreciated, as none of the ones I've been able to Google up have been acceptable.

4) Bitrates. Many of my AVI files aren't of the highest quality. Certainly, full DVD bitrates of 4 Mb/s are not necessary for the mpeg2s I'll be producing. It's a big waste of bits, as I'd like to get as many files on a DVD as possible. Is it the case that the Best button accurately determines the lowest possible bitrate that doesn't reduce the quality of a file? Is there a calculator someplace else I should use? I want to be able to say I have an X by Y file of type T, encoded by video codec C at bitrate B and get an approximate required bitrate for another file type (eg mpeg2 for DVD burning) and resolution. Please let me know if I have any misconceptions here.

5) "Decode with Quicktime"? I haven't been able to find good information on what this option does. I assume this specifies which program is used to output RGB JPGs which are then reencoded into the target file format. I've read that deselecting this option can result in performance gains of up to 100%, but I have seen no mention of how quality is affected. Additionally, what program does ffmpegx use instead of Quicktime if this options is deselected? mplayer?

Thanks in advance for your assistance, gurus of the video conversion world.

[TugBoat]

Since our Mods still haven't moved this to the ffmpegX forum, you might try reposting there.

I think you kinda overdid it with too many questions at once

But;
1) I don't use Sizzle or Toast for encoding/authoring, so....

2) I've never used Mpeg2works, so...

3) Ah! A topic close to my heart, AVI resolutions. Yes they have many different sizes and most of the time they are wrong. I've been using ffmpegX on AVIs and it's easy to correct the aspects as long as you understand your question 5.

5) The biggest use of Decode with QT is for Automatic Letterboxing. It is also supposed to give better control over frame rate changes as when a DVD goes from 23.98 to 29.97 and back. AVIs don't change framerates like commercial DVDs do. So, I really don't see any use in using Decode with QT, and you CAN'T use Manual Letterboxing OR Cropping if you select Decode with QT. I don't use it.

3-4) The standard bitrate for full DVD is 4000 at 720x480. most Mpeg2 encoders will give good results at these resolutions. I am impressed with the ffmpeg codec's ability to give good results at lower bitrates. That's why I'm using ffmpegX to convert AVIs to multitrack DVDs. To enable extremely low bitrates, you would choose to use the Half D-1 resolution of 352x480. DVD Players will recognize this setting and display it as normal size (720x480) on screen.

Since you're using half the resolution, you can use half the bitrate and it will still look good on a normal standard definition TV. Since the AVIs usually aren't DVD quality anyway, the mpeg2s, at half resolution, will usually look as good as the AVI. Half Bitrate means you can put twice as much in the same space.

3) The best way to correct the AVIs resolution is trial and error. It's easy when the settings are obvious, like a 4:3 movie set as 16:9 or visa versa. Or the 16:9 movie with useless Letterboxing (Crop the shit out of it). Most movies I run across are 16:9 or less. You can use QT Pro to play around with the Video Size and see what settings are appropriate. Just remember that it's best to use settings that are multiples of 16. Adjust the horizontal size to 720, and then see what vertical size looks best.

Then, remember that whatever Letterboxing settings you make, the total HAS to be 480. I always use the Half DVD setting of 352xXXX where XXX is the result of 480 minus the Letterbox settings. Example, Movie is originally 640x272...it's wrong....Peoples faces are not that squished, wheels are usually round, etc... I found that using the settings 352x400 with 40/40/0/0 Letterboxing and 0/0/4/4 Cropping produces a better looking movie. A quick look with QT Pro shows 640x272 expanding to 720x306. Adjusting the vertical to 320 looks better. Even though the encode will be to 480, it will be displayed as 720x400 (16:9). 400-320=80/2=40...400+40+40=480 :P

Note that there is currently a BUG with ffmpegX where a MPEG produced at this setting will be displayed as 4:3 when using the Half DVD setting. You can use HexEditor on the demuxed M2V to correct this display error and set it to 16:9. I use DVDSP, and setting the track as 16:9 fixes this error without HexEditor. But this does present a problem with the built-in preview in ffmpegX.

Since most of the AVIs are close to this size, I've set MPlayer OS X 2 to always display 16:9 and use that to preview the ffmpeg mpgs instead of the built-in Preview on ffmpegX. That way, I can easily preview the mpg in it's infant stages to see if it's acceptable. It will be nice when they fix this BUG.

So, to fix resolutions, use the ffmpeg Codec without the Decode with QT option and set your manual Cropping and Letterboxing for the best looking movie.
Lotsa fun.