Or, before you add the standard definition clips to your project, you can go to Edit/Preferences/General and check the Scale to Frame Size option. You video still may not fill your frame side to side, but at least it will top to bottom.
You can also manually enlarge the clip if you want by selecting it on your timeline, opening Applied Effects/Motion and changing its Scale. You can then make it fill your video frame -- but you'll do so by trimming off some of the clip's bottom and/or top.
Regardless, you've also got one other issue. I don't know what you plan to do with your video once you're done editing it but, if you plan to output it as a high-def video (a BluRay for instance), you've got one other problem. Your clip 2 is less than one-fourth the resolution of clip 1 -- so, if your project is set up for your high-def video, enlarging the standard-def video could make it look fuzzy or blurry.
If the PAR (Pixel Aspect Ratio) of Clip 2 is correct, i.e. the footage does not look stretched, or squeezed, I would not make any adjustments to that.
To reduce, or completely remove the black bars around it, you can adjust the Fixed Effect>Motion>Scale, to fill the larger Frame Size. Note: because of the difference in the footage's Frame Aspect Ratio, to fill the full Frame of the Project, you will effectively crop off some of the top and bottom. By using the Fixed Effect>Motion>Position, you can adjust exactly where the cropping takes place, say all from the top, or all from the bottom, or by a different ratio of top & bottom. That choice should be predicated by the framing of the subject in Clip 2. That choice is yours.
Note: when Scaling up, quality will decrease, though possibly not by too much to use that footage, but the decision is also yours. There are several programs, and some that are plug-ins, that up-rez a bit better than Motion>Scale in PrE. I would investigate those. One, Red Giant's Magic Bullet Instant HD, has been used by many, though some users were not pleased enough to purchase it. Just something to consider.
I have two clips:
clip1: AVCHD 1440 x 1080 and pixel aspect ration of 1.3333 (the frame ratio is 4:3)
clip2: AVI 720 x 576 and pixel aspect ratio of 1.0940 (the frame ratio is 5:4)
I want to use both clips in the same project.
Based on the above, your "display aspect ratio" is going to be either 4:3 and 16:9.
In the case of the AVCHD 1440 x 1080 that you cite, that is 1440 x 1080 HD anamorphic 16:9 indicating that the 1440 x 1080 is stretched by that 16:9 flag to 1920 x 1080 for display after encoding.
In the case of your 720 x 576 with the pixel aspect ratio = 1.0940, that is 4:3, not 16:9 (widescreen).
As you know, Premiere Elements allows for one project preset and that should match the properties of your source media. When you have a mixed Timeline (varied video formats/frame aspect ratios/pixel aspect ratios/and display aspect ratios), then priorities need to be set.
What I would suggest you look at if it has not been mentioned before or if you have tried it is the following:
If you want a HD export
Premiere Elements XX project preset (new project dialog) = PAL AVCHD HD1080i25
Drag the imported 1440 x 1080 HD anamorphic 16:9 to the Timelne
Import the 720 x 576 into the project and drag it to the Timeline
Scale the 720 x 576 to fill the space in the Edit Mode Monitor (quality may deteriorate scaling 720 x 576 to 1920 x 1080 space, but give it a try. It may give you surprisingly acceptable results.
a. consider a SD project counterpart where you scale down the 1440 x 1080 HD anamorphic 16:9 to fill the 720 x 576 space in a PAL DV Standard project.
b. consider keeping the HD project and using the SD in a picture-in-picture type arrangement in the 1920 x 1080 Edit Mode Monitor space.
For HD export, I would look at the 1920 x 1080, rather than 1440 x 1080 HD anamorphic 16:9 choices, such as, /MPEG/with preset
MPEG2 1920 x 1080i25 (gives .m2t file) or /AVCHD/ with preset MP4 H.264 1920 x 1080p25 (giving .mp4 file).
As far as the two clips goes the solution of scaling up clip2 seems to work. (I could try the picture in a picture thing as well; sounds interesting).
However; you have opened a new can of worms for me. clip1 is 1440 x 1080 Pixel Aspect Ratio of 1.3333. I've used a project preset of PAL AVCHD HD1080i25 (as you suggest). But I don't understand what you mean by anamorphic.
I have output the clip (just clip1) as a movie twice once at 1440 x 1080 and once at 1920 x 1080. In fact the widescreen one (1920 x 1080) looks a bit more 'normal'.
Ok. I think I have partly understood this. The output movie at 1440 x 1080 still has a pixel aspect ratio of 1.3333 but the output movie of 1920 x 1080 now has a pixel aspect ratio of 1. So it looks like Premiere Elements automatically sorted that out, changing the pixel aspect ratio as it changed the ratio to true widescreen. The 1920 x 1080 one looks better in Quicktime (both look ok in Windows Media Player because it plays both at the same size).
Confusingly WIndows Media Player seems to play both these at 16:9 but Quicktime player sticks to the actual frame size.
You've suggested I use 1920 x 1080. Can you explain why? Are computer monitors generally square pixels? If it was going to be broadcast (which it is not) which should I use?
Your entire workflow all depends on what your end delivery is going to be.
Are you going to make a dvd or BD or just for the web?
Scaling clip 2 completely (that is without black bars and loosing top an bottom of the clip) up in a HD environment is going to be a disappointment. Scaling is going to be 250%. Rather a lot.
Clip 2 is 4:3, you will have to settle for black bars on each side the scaling will be 'only' about 200%
an you can fill it with a blurred background from the same clip.
The settings are PAL - avchd HD 1080i 25.
Next time film in 1920x1080, that will make things less complicated (get a larger card).
1440x1080 has a different pixel aspect ratio (1,33) then 1920x1080 (1.0).
To make things a bit complicated 1440x1080 is actually 4:3 but with a pixel aspect ratio of 1.33 it will display as widescreen.
This type of format is called anamorphic, so is clip 2, but just forget all about it.
To avoid 1440x1080 being displayed wrong (which means the video is stretched in the length and depending on which format you use also) export to 1920x1080.
Here is my take on all this.
As I said, 1440 x 1080 HD anamorphic 16:9 and 1920 x 1080 16:9 square pixels will both display at 1920 x 1080. One needs a flag to direct the player to stretch the video, the other does not.
That Pixel Aspect Ratio of 1.3333 is a correction factor so that the 1440 x 1080 displays after encoding as 1920 x 1080. That 16:9 flag depends on the player respecting the pixel aspect ratio to display the video at 1920 x 1080.
One of the major functions of setting the project preset is to direct the program to set up a space in the Edit Mode Monitor from which to edit your video. That monitor space for your 1440 x 1080 HD anamorphic 16:9 is not 1440 x 1080, but 1920 x 1080 to reflect the display space.
One way of thinking is that selecting 1920 x 1080 instead of 1440 x 1080 HD anamorphic 16:9 at export bypasses the opportunity for the player to misinterpret or having problems with the flag directive to take the exported 1440 x 1080 to 1920 x 1080. No need if you export 1920 x 1080.
I can go further into square pixels (1.0) which is associated with 1920 x 1080 if you want. But for now I will see if what I wrote has been helpful.
Add On...After I posted this message to you, I saw the post exchanges between you and Ann Bens.
My choice of project preset would be PAL AVCHD HD1080i25 and focusing my attention to the 1920 x 1080 export choices as suggested by my earlier posts.
Yes, This has been fantasitically helpful. And Ann Ben's contributions as well. Really nice to get such clear immediate answers, for someone just starting out.
I have discovered that on Windows 7 Quicktime doesn't respect the pixel aspect ratio and so the 1440 x 1080 export is 'squashed' whereas Windows Media Player does. To be safe therefore I will export as 1920 x 1080. (Premiere Elements seems to know to set the Pixel Aspect ratio to square). Which means, as people have said, I don't need to worry about what it is being played on.
But, also, I've decided to use the 1920 x 1080 recording mode on my camera and it looks like I have to buy a bigger memory card.