Encoding and Aspect Ratio Tip.

By | March 7, 2008

Last night I put on The Condemned as I had not seen it and was in the mood for some action. Once it started, I noticed that there was something odd about the way it was displayed on the screen. I knew it was a 16:9 movie and I have a 37″ Hannspree XV37 widescreen LCD in my bedroom, but it was displayed more like a 4:3 movie with no black bars. Something was wrong.

I have this movie in Blu-Ray, so I checked it out. Sure enough, it’s in 1.78:1 widescreen. I then used MediaInfo to check the details of the mp4 I had encoded. I reduce the resolution to an acceptable one for most all my HD movies. It saves on space and still provides an excellent picture. For this one, I used a resolution of 800×448. However, for some odd reason, it had a PAR (picture aspect ratio) of 1.5:1. Crap.

Well, I’m pretty picky about things like this and I refused to watch the movie. But I’m also too stubborn to submit myself to ripping and encoding this thing all over again. What ever will I do?

After some Internet scrounging, I found out that MP4Box can alter the PAR. I already had YAMB installed, so I just took the MP4Box executable out of there and dropped it in my C:\Windows directory. I coped The Condemned to a local directory from my server and renamed it to take out the space, then ended up using this command:

C:\>mp4box -par 1=1:1 x:\archange\condemned.mp4

After it completed the ISO writing, I opened it up in MediaInfo and voila! 800×448 (16/9) love! I renamed it, copied it back over to my server, and went back to bed to watch Band of Brothers instead.

So, if by mistake, you or your encoding software incorrectly sets your PAR to something other than the intended one for your mp4 files, this is a good way to change it. Keep in mind that it may not always be 1=1:1, however. I ended up having to change a couple of others using 1=8:9 (which is 4:3 fullscreen) and 1=32:27 (which is 16:9 widescreen). These were encoded in true DVD resolutions of 720×480, but were showing a 1:1, which made them display at 1.5:1. For fullscreen material, this looks very close. It’s not acceptable for widescreen, however.

I could get into PAR, SAR (sample aspect ratio), and/or DAR (display aspect ratio), but I’m afraid I’d just confuse my point here. I’d probably confuse myself as it can be harder to preach than practice.

Hope this helps someone out. Let me know what you think (comment/register). Happy encoding!

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