Am I calculating resolution correctly?

[alcOre]

Ok...so I've been calculating my target resolutions a certain way for a year now and I'm wondering if I'm even doing it the right way. There are certain things that I've noticed that make me doubt I'm doing it entirely correct.

I use MeGUI to help me determine my target resolution for my transcodes. My source material is usually my dvd movies, or music videos. I transcode to AAC/H264 for my iPod Touch. Here's my process, using The Last Samurai as an example.

I index using DGIndex. I then load up the index file into MeGUI. I crop the black parts out so that all I have is the film with no black borders. For my example movie, I crop 64 pixels off the top and 60 off the bottom. I then click on "Clever anamorphic encoding" and change to the Edit tab. I then use the global MeGUI_darx and global MeGUI_dary values to determine my target resolution. iPod touch/iPhone supports max 480x320 resolution. Since this movie is widescreen, I want my X resolution to be 480. In my example, the global MeGUI_darx value is 145 and the global MeGUI_dary value is 59. Since I know my target X value is 480, I calculate my target Y value like this : Target X * global MeGUI_dary / global MeGUI_darx = Target Y, so 480 * 59 / 145 = 195.31. So I would then go back and uncheck clever anamorphic encoding and set my resolution to 480 x 196 (rounded 195 up...and PS I don't care about Mod16.) Here's the thing though. I compared this to The Last Samurai on iTunes (my sister purchased it) and mine looked like it was wrong. The Last Samurai's AR is 2.40:1. If you take my example, my video's AR ends up at roughly 2.46. So I have to be doing something wrong right? Here's the other thing. If I change one thing in my process it ends up being correct. Lets start from the beginning. I load up the d2v, but then instead of leaving the Input DAR at what MeGUI detected (in this case ITU 16:9 NTSC), I change the input dar to 1.778. I then do everything else like before. I crop the black bars, I choose Clever Anamorphic Encoding, and get the global MeGUI_darx and global MeGUI_dary values. I then use the previous formula. In this case with the new global MeGUI_darx and global MeGUI_dary values, I end up with a resolution of 480 x 200. 480 / 200 is an AR of 2.4, like it should be. I was told to leave the input DAR at the ITU values though. But when I change it to 1.778 I get the correct AR on my final encodes. Can someone please tell me what I'm doing wrong? PS...sometimes on some movies, I get closer to the movie's original AR when I leave the input DAR at ITU values instead of 1.778. I notice that when the original movie's AR is 1.85, then if I leave the input DAR at ITU values my calculated resolutions are closer to original AR, but the "wider" ARs are better when I use an input AR of 1.778.

Sorry the question is so long, I just need to figure out where I'm going wrong.

alcOre

[alcOre]

bump... (sorry, I just need some answer.)

[jagabo]

The difference between ITU 16:9 NTSC and 1.778 DAR is whether the 16:9 image is contained in a 704x480 portion of the frame (ITU 16:9) or the full 720x480 frame. Even with ITU 16:9 the extra 16 pixels (8 on each side) may contain valid picture information. If you retain it the frame is slightly wider than 16:9.