Are you exporting digital video, want to upload it to a video sharing site and wondering what resolution and pixel aspect ratio to choose? This article offers some suggestions. Some of the suggestions may seem too complicated given the title of the article, but it’s a surprisingly tricky topic, especially when dealing with standard definition (SD) widescreen formats.
PAR, DAR, Pixel Dimensions
Display Aspect Ratio = The ratio of the width to the height of the entire image (widescreen is 16:9, non-widescreen is 4:3)
Pixel Aspect Ratio = The ratio of the width to the height of each pixel that makes up the image
Pixel Dimensions = The width and height of the images measured in terms of pixels (e.g, 1280 x 720). In this article, I will refer to pixel dimensions as ‘resolution’.
The Pixel Aspect Ratio Problem
Computer monitors display images using square pixels (i.e., a pixel aspect ratio of 1:1) and video-sharing sites like Vimeo and Youtube prefer uploaded videos to be in formats with square pixels. However, standard video formats like PAL and NTSC, which are based on their respective television broadcast formats, produce images using rectangular pixels. For example, PAL video (standard definition, non-widescreen) has a display aspect ratio of 4:3, a pixel aspect ratio of 12:11 and pixel dimensions of 720×576.
Another example involves high-definition video. While full HD video (1920×1080) uses square pixels, anamorphic HD video (1440×1080) uses fewer pixels, but because the pixels are rectangular, the image is stretched out so that it appears as large as full HD video.
In short, there is often a mismatch between the video format (based on rectangular pixels) and the display format (based on square pixels).
The Good News
Almost all computer media players will happily play video with rectangular pixels so that they look fine on a computer monitor. Web uploading sites like YouTube will also automatically convert your video into a format using square pixels when transcoding your video.
- Example 1: If you upload an anamorphic HD Pal Video (1440 x 1080), YouTube will convert it into a 1280 x 720 HD video with a pixel aspect ratio of 1:1 (YouTube’s 720p viewing option).
- Example 2: If you upload a PAL SD Video (720 x 576), YouTube will convert it into a 640 x 480 video with a pixel aspect ratio of 1:1 (YouTube’s 480p viewing option).
The Bad News
You may not like the conversion job done by YouTube (though I think there transcoder is much improved. Also, video uploaded to some sites like Vimeo tend to work work better if they are uploaded in a standard square pixel format.
If you are working with:
- HD video at 1920 x 1080 (square pixels), you can export it at 1920×1080 or 1280×720 (also square pixels). If think you will use the video a few years from now, go for the higher resolution
- HD video at 1280 x 720 (square pixels), export it at 1280 x 720.
- Anamorphic HD video (1440 x 1080) and want to play the video on a media player or make a DVD, you can export your video at that resolution without changing the pixel aspect ratio.
- Anamorphic HD video (1440 x 1080) and you want to upload the video to a video site, you can change the resolution to 1280 x 720 and change the pixel aspect ratio to square pixels (You can also just leave the resolution and pixel aspect ratio as they are and let the video site do the transformation for you).
- Standard definition video (PAL or NTSC) and want to make a DVD or play the video on your computer, just go with the default settings (i.e., don’t change the resolution or aspect ratios).
- Standard definition video (PAL or NTSC) and want to to upload it to a video site, you can let the video site try to convert the aspect ratios, or you can do it yourself. This is tricky, especially when working with widescreen formats, so I would suggest that you try the default settings first (Just select a preset (e.g., PAL-DV, PAL Widescreen-DV, NTSC-DV, etc.) in your video editing or exporting programme, don’t change the resolution or aspect ratios) and see how things turn out once your video is uploaded . If you don’t like the results, you can consider the following suggestions:
PAL 720 x 576 (non-widescreen)
You want a display aspect ratio of 4:3 and pixel aspect ratio of 1:1. Change the pixel aspect ratio to ‘square pixels’, crop some pixels of each side (Premiere Pro will crop a total of 17 pixels off the left and right sides; for example, 8 from the the left and 9 from the right side. Cropping 16 pixels might be enough, so you can test out both options.) and export the video at a resolution of 704×528 or 640×480. If you don’t crop the video, when you export it, your video exporting programme will likely either add black bars to the top and bottom of the video (known as letter-boxing) or will stretch out the video, making objects appear slightly distorted. Letter-boxed video will look OK on your computer monitor, but when you upload it to YouTube, you will also get black bars on the side. Your video will be smaller than it should be and will surrounded by black bars on all four sides (ugly!).
NTSC 720×480 (non-widescreen)
You want a display aspect ratio of 4:3 and pixel aspect ratio of 1:1. Change the pixel aspect ratio to ‘square pixels’, crop a total of around 15 pixels off each side (e.g., 8 from the the left and 7 from the right side) and export the video at a resolution of 704×528 or 640×480 (exporting at the latter resolution will create a smaller video, but it will match YouTube’s 480p pixel dimensions).
PAL Widescreen (720 x 576) and NTSC Widescreen (720 x 480)
The solutions are very problematic and may vary depending on the camera that you are using and the website you are uploading to, so you will need to experiment with different resolutions when exporting (or you may just keep the default resolution and pixel aspect ratio and hope for the best). I would suggest experimenting by exporting a short clip (e.g., several seconds long) using different resolutions and seeing which one works best. Basically, you are looking to change the pixel aspect ratio to ‘square pixels’ (i.e., 1:1) and change the pixel dimensions so that they are at a 16:9 ratio.
You can try downsampling to 640 x 360 or 512 × 288 (or 524 x 288 for PAL video, according to some websites), but the video will then be quite small. You can also upsample to 1024 x 576 (or 1048 x 576 according to some websites). It is even possible to upsample it to HD at 1280×720. Upsampling (increasing the resolution of an image or video) is generally a bad idea because you are not really increasing the resolution, you are just making the image dimensions bigger (To understand this, try zooming in on a photo in your computer. The image on the monitor will get larger, but after a while the pixels that make up the image become more and more obvious). I would only suggest using this upsampling method as a last resort, but it is one method of dealing with PAR problems when exporting video in widescreen formats.
I did this lind of upsampling (up to 1280 x 720) for one video and it looked OK on YouTube (though admittedly the video ended up with a ‘soft’ look); what this approach did was to get YouTube’s transcoder to accept and convert the video into an appropriate standard definition widescreen format without any letter-boxing.
Fot NTSC Video, you can try the following dimensions: 960 x 540, 853 × 480, 854 x 480 (recommended by many websites and the closest to a 16:9 widescreen ratio) or 856 x 480 (the composition settings After Effects uses for NTSC widescreen). You may need to crop pixels off the side (try a total of around 15 pixels of the image) when exporting it.
Why are there sometimes two different sets of dimensions for the width (e.g., 1048 or 1024; 524 or 512)? It depends on how your camcorder interprets the widescreen display aspect ratio—that ism whether or not is follows the traditional PAL format iin which extra pixels are added to eiher side of the image.
I find trying to get widescreen formats, standard definition and square pixels to get along with one another is very problematic. I would suggest that if you want to work in widescreen, go for HD video. Life becomes so much easier. If you are working with Full HD video your source video, editing project settings and exported video will use square pixels. Even if you are working with anamorphic HD, it is easy to export it at 1280 x 720 HD.
Note: Video transcoders work better when your dimensions are multiples of 16. (e.g., 1920, 1280, 720, 704, 640, 524, 480, 360, etc.). YouTube’s transcoder prefers these standard pixel dimensions and but can usually handle other dimensions (like 853 x 480).
Let me know how these settings work or if there are any problems with the suggestions.
My Other Articles on Video Editing
- Exporting HD Video for YouTube: Premiere Pro CS3 & CS4
- Choosing Premiere Pro Project Settings for HD Video: Very important, as it is difficult to change project settings once you begin
- Changing Project & Sequence Settings: Premiere Pro CS3 and CS4: Premiere Pro CS3 & CS4
- Premiere Pro CS4: Maximum Render Quality: For better image quality, especially with video of fast-moving objects
- Exporting Video for YouTube: Pixel Aspect Ratio Basics: How to get a pixel aspect ratio of 1:1
- Troubleshoot Export Failures: What to do when you see the error message: Application Failed to Return a Video Frame
- Exporting Video for Nico Nico Douga: Recommended settings