Aspect Ratios

Kiwidino wrote on 10/26/2010, 10:45 PM
Camera: Canon Legria FS200 (SD, PAL, Widescreen)
Software: Sony Vegas Movie Studio 9 Platinum Edition
Problem: Widescreen aspect ratios

OK, so here’s what I have learned. Let’s see if I’ve got this right. There are two aspect ratios to be concerned with - the Display Aspect Ratio (DAR) and the Pixel Aspect Ratio (PAR).

Let’s start with the Display Aspect Ratio. In simple terms, we can think of this as the output or playback. Old fashioned CRT televisions have a DAR of 4:3. The newer television format, often described as “widescreen”, has a DAR of 16:9. The first figure in each ratio refers to the width and the second to the height. With 4:3, the width is 1.3333 times the height (4 / 3). With 16:9, the width is 1.7777 times the height. We will ignore others, such as cinema screens, for now. Most (all?) High Definition (HD) material is in widescreen, but by no means is all widescreen material HD. I am attempting to create Standard Definition (SD) output in widescreen, because my camera and therefore my source material is SD, not HD.

Next we have the Pixel Aspect Ratio. This is a little more complicated. When we shoot video on a standard definition camera, it is in either PAL or NTSC formats. These are different standards used in different geographic regions. PAL camera footage is always 720 x 576 pixels and NTSC is always 720 x 480 pixels. Strangely, neither of these ratios is the same as either of the standard display aspects (4:3 or 16:9). PAL, at 720 x 576, has a width of 1.25 times height, close to the 4:3 DAR of 1.3333 and nowhere near the 16:9 ratio of 1.7777. NTSC, at 720 x 480, has a width of 1.5 times height, somewhere in the middle. The reason all this can still work is that individual pixels do not have to be square. If we look at the ratio of an individual pixel (not the PAR, which is the number of rows and columns of pixels in a frame), a “square” pixel would have the same width and height and would have a ratio of 1:1. But pixels can be rectangular – with a different width to their height.

My camera has a widescreen (16:9) display. It has options to record in either 16:9 (widescreen) or 4:3. I have it set to widescreen because my television is widescreen, I will output to DVD, which is widescreen, and upload to You Tube, which is widescreen. I use PAL because where I live (New Zealand) all hardware is PAL and I will send DVDs to family and friends in the UK, where the standard is also PAL.

Now, it took me a while to get my head around this and I hope I’ve got it right. I understand that regardless of whether I set the camera to 4:3 or 16:9, it will always record 720 pixels by 576 pixels. How is that? The answer is – variable pixel widths! I have no idea how that works. Apparently the camera adjusts the pixel width to suit the format.

I believe it is best practice to only ever mess with the width, never the height (something to do with potentially being played back on an interlaced screen versus progressive).

So here’s the thing. I have my raw footage in PAL widescreen 16:9 MPEG 720 x 576. I bring this footage into my Sony Vegas Movie Studio 9 project, which I set as a Widescreen project when I started it, and by default, the aspect is all wrong! The footage appears in 4:3 aspect (with black bars down the sides, because it’s a widescreen project) and all the people look tall and thin. I can fix this in one of two ways. I can right click the event in the timeline and either:
a) select Switches and un-tick “Maintain Aspect Ratio” (which seems an odd thing to do); or
b) select Properties / Media tab, and change the Pixel Aspect Ratio to 1.4568 (PAL DV Widescreen) using an option from the drop-down list.

Now, finally, here are my questions:
1) Why do I have to do this for every clip? Where I have extracted more than one section from a clip and placed them in the timeline, I only have to do this for one event and it affects all events from the same clip. But I have to do it for an event from EACH clip. This is inefficient and it’s easy to miss one, which is frustrating when you find it after you’ve rendered. Why, when the source material is recorded in widescreen and the project is widescreen, do I have to do this at all? Is there a smarter way? Why does Vegas insist on taking widescreen footage and “squishing” it horizontally into 4:3, distorting it in the process, when it could just leave it the heck alone and it would look fine?
2) When changing the pixel aspect ratio on the Properties/Media tab, I would expect to change it to 1.422216 (because 720 x 576 is a ratio of 1.25 and I want it to be 16:9, which is 1.7777 – so divide 1.7777 by 1.25 and I get a scaling factor of 1.422216). But there is no option for this in the drop down list on the Pixel Aspect Ratio box. Using 1.4568 works and I guess I should just be happy with it, but it would be nice to understand.

Now let’s talk about output and rendering. I can render the project in any of several formats (avi, mpg, etc.) and it looks fine. It plays on the PC fine. Upload it to You Tube and it squishes it to 4:3, distorts it and adds black bars at the sides. Through trial and error, I have found that if I render as HD Mpeg using a format of "MainConcept MPEG-2 and a template of HDV 720-25p" (ridiculous, because the source material is not HD), I get a file extension of M2T. My PC won’t play that (even though it can create it), but I understand it’s an Mpeg format, so if I rename the file and change the extension to .mpg, it will play on the PC. I then upload to You Tube and it works! It picks up an inappropriate HD logo, but it works. Is there a better way? Can I render as something more sensible (not HD) and have You Tube accept it for what, to me, it clearly is - i.e. SD widescreen?

I would really appreciate answers to these questions and pointers if I’ve got any of the above incorrect. I now know an awful lot more about video than I ever wanted to, but I’ve started down the journey, so might as well see it through.

Comments

Rainer wrote on 10/27/2010, 1:46 AM
Hi Kiwidino, You had me intrigued because everything works as it should, 4:3 and 16:9, from my Canon and Sony tape cameras. Turns out the FS100 records in mod format and 16:9 mod is not correctly identified in the media file header. Sektionschef has written a neat utility, SDcopy, which sets the flags correctly, get it at http://zyvid.com/smf/index.php?action=dlattach;topic=280.0;id=153, Google for more info if you need it. YouTube seems to handle most formats nowadays, your best option is Sony AVC 640X360-25p.

Chienworks wrote on 10/27/2010, 3:37 AM
Agree with Rainer, your camera isn't setting the aspect ratio in the file headers properly. The fixing utility should help you out a lot.

I'll also point out that in SD-land, the display aspects are not 4:3 or 16:9. They're both just a tad wider than that. "Normal" is 4.09090909:3 and "widescreen" is 16:36363636:9. Vegas does it all right so just use it's presets and don't worry about the math.

When rendering make sure you choose the widescreen template there as well! It doesn't help to have your entire project set properly as widescreen if you end up rendering to a 4:3 template.
Kimberly wrote on 10/27/2010, 6:23 AM
Hey Kiwi:

I may have missed this in your post, but when you are setting the project properties, are you selecting "Match Media Settings" and saving this as a default for all future projects?

Choose Project/Properties. On the "Video" tab the first option (in VMS 9.0) is "Template." It sounds like you've already figured out which template to use based on PAL, SD, etc.

BUT if you look over to the right of the "Template" option, there is is a Save, Delete, and File icon. I never looked at these until someone on the Forum told me about the File icon.

Hover your mouse over the File icon and you should see that is says "Match Media Settings." That should cause your entire project to display correctly and your shouldn't have to mess about with the aspect ratio for each clip. Of course if you have manually set the properties for clips, this will override the general project properties and you may have to remove the manual settings or reload your clips or whatever.

The File icon is a little misleading. You would think Sony would put an icon of a video clip or Equals Sign ( = ) or something there to draw attention to this important option. But they don't.


Kim

Kimberly wrote on 10/27/2010, 6:34 AM
Here are some ideas on your render:

I have found that the MainConceptMPEG-2 is a good template for SD and HD.

When doing SD, I choose the template "DVD Architect NTSC Widescreen video stream." For you that would be "DVD Architect PAL Widescreen video stream."

Be sure to check the box on the "Stretch Video to Fill Output Frame (do no letterbox)" option.

On uploading to YouTube, I have just one SD Widescreen video there. It has tiny black bars along the top and bottom. It plays okay and the resolution is okay but not great. Look for posts by Eugenia concerning the best settings for YouTube. She has some excellent advice on that subject.
Kiwidino wrote on 10/27/2010, 11:21 AM
Thanks Kimberly, but using the File icon to Match Media Settings made it worse! It made no difference at first (still got squished 4:3 on my raw footage) but now when I set the media properties manually to 1.4568 Widescreen, it adds letterbox black bars top and bottom and distorts it vertically. None of which affects the next clip I open, which still displays in 4:3.
Kiwidino wrote on 10/27/2010, 11:26 AM
Thanks Rainer and Chienworks. FS200 also records MOD files on the SD card. I get them onto the PC using the 3rd party software which came with the camera (Pixela Image Mixer 3 SE). In using this, it converts them (at least, it changes the file extensions) to MPG. I guessed this was necessary as MOD I thought MOD was a non-standard format. Otherwise I would just copy from the SD card using Windows Explorer. Then, in VMS9, I use the Explorer function to preview the files and open them in the Trimmer. Select the section I want and drop it into the timeline. From your description, talking about VMS handling the MOD files, I guessed you might be using the Capture feature. So I tried this but it won't recognize the camera. The Capture help talks about the firewire connection. My PC has firewire, but the camera only has a USB connection. Haven't tried the utility which you recommend yet. Will do shortly.
Kiwidino wrote on 10/27/2010, 11:40 AM
Hey Rainer. I tried that SDCopy utility, setting the widescreen flag. That certainly seems to have fixed problem 1. Irritating though - shouldn't be necessary.

Chienworks, thanks for explaining the maths on problem 2. Still don't really know why, but can accept it and move on.

Kimberly - good tips re rendering output. I will try them.

Thanks to all for taking the time to respond.