Nokia's Communicator devices are advertised and also considered as business devices, with features designed for the corporate people. The latest Nokia E90 Communicator however is based on the common Symbian Series 60 platform, and it boasts cutting edge mobile multimedia features as well. In fact, the E90 with it's high quality 800x352 display and a powerful DSP processor for multimedia is actually one of the highest performing mobile video players on the market! The wide PDA side display is almost ideal for viewing video content and even movies, while stereo headset provides good quality audio. This guide tells you how to transfer your AVI video files into MP4 format supported by the E90 with very high-quality results, so that you enjoy your movies or videos on the road conveniently. And best of all, this is achieved by using free software.

This guide is mainly for the advanced users who want to take out the most of it, and some background information and knowledge is required in order to fully utilize it. In the guide we’ll discuss about aspect ratios, encoder's settings and video filtering. All programs used in this guide are freely available.

STEP 1: Making Decisions about Video’s Aspect Ratio

Firstly, few words about aspect ratios. As we’re encoding videos for E90, there are few tricks to be made regarding the aspect ratio. As you may already know, E90’s screen’s native resolution is 800x352 pixels. That brings up few challenges with certain videos.

So, let’s see some basic stuff about aspect ratios. Note that we’re dealing with display aspect ratio (DAR) here. E90’s DAR is 800/352 = 2.272727…, which is pretty close to anamorphic widescreen, 2.35:1, which is commonly used in DVDs. Thus videos with that AR would be optimal for E90.

Unfortunately there are also other types of aspect ratios: widescreen 16:9 and fullscreen 4:3. You can make few compromises with 16:9 widescreen if you’re not too perfectionist about aspect ratio (AR).

Here are few examples about the all three situations:

The green layer pretends to be E90’s display. First from left is anamorphic widescreen, second one is 16:9 widescreen and the last one is 4:3 fullscreen.

The anamorphic widescreen, 2.35:1

So, let’s take a closer look at the first example. In general, we have to choose between two options:

1. Keep the AR by adding little black bars in the video
2. Ditch the AR calculations and resize straight to 800x352

In this case, resizing straight to the E90’s native resolution is a good choice, because the AR error is very small, only 3.3 percent. Here are examples about the two choices explained above:

This is a matter of an opinion. You are the one watching the video, so the decision is yours. I think that AR errors less than five percent are acceptable, so I would go with scaling directly to 800x352.

Note: If your video’s AR is bigger than ~2.27 and you want to keep the correct AR, the black bars will be inserted on top and below the actual picture. This is the only case where the bars will be placed like this!

The widescreen, 16:9 ~1,777…

The second example is one step worse than the first one. If you stretch the video discarding the correct AR, error is much bigger than in the first example.

But again, some people may want to enjoy the full benefit of E90’s display and bear the AR errors. I personally would go with the correct AR with black bars.

Note: The black bars will be added on the left and right sides of the actual picture.

The fullscreen, 4:3 ~1,333…

This is the worst case scenario. If you want to keep the correct AR, black bars will eat almost 42 percent of effective display resolution. If you decide to go with ‘the dummy way’ and scale the video straight to 800x352, the aspect ratio error will be huge. In my opinion, it’s way too much. Of course you could make compromises and use thinner bars, but the AR will still be incorrect. Again, I wouldn’t personally make compromises with AR in this case.

Note: Also in this case, the black bars will be on the sides of the picture.

Few words about HD videos

As you may already know, there are not only different types of aspect ratios, but there are also different kinds of resolutions. Here is an example that has a resolution of 720p which is both horizontally and vertically bigger than E90 display’s resolution. Thus it needs to be down-scaled to 800x352. On the contrary there are also many situations when video needs to be up-scaled. This is the bottle neck of the ‘one-click’ tools; they can’t deal with both up-scaling and down-scaling.

The same rules apply to HD clips; they can come with different ARs.

Calculation the Aspect Ratio

If you want to use the full 800x352 screen resolution without black bars, you can ignore all the math stuff below and move onto next step.

If you decided to keep the correct aspect ratio, you need to do some calculating for it. First thing you need to do, is to find out your video’s resolution. You can use e.g. VirtualDub or Windows Explorer’s properties dialog to find out the resolution.

Example 1: AR bigger than ~2,27

In this case, your resolution is 624x256. This would be the same as in the first example, thus it has AR of ~2.44. That means that we’ll have to add bars on the top and below the picture. This implies that the horizontal resolution will be 800 pixels. Here’s a simple formula to calculate the vertical resolution:

Since resizing algorithms work the most effectively with mod 4 resolutions, so you should ensure that your resolution is mod 4.

Now, we know that our video’s resolution will be 800x328. Now we need to calculate the amount of black bars to be added. That’s fairly easy:
(352-328)/2 = 12, which is the height of one bar. So, now that we add 12 pixels of black bars on top and below the picture, our vertical resolution will be 328+12+12 = 352.

The two other situations will be dealt with similarly. But in these two cases, black bars will be added on the sides of the videos, so we need to calculate the horizontal resolution instead of vertical one.

Example 2: AR smaller than ~2,27

Let’s take a have a look at this example: Say that our video’s resolution is 696x430 which gives AR of ~1.62. Here’s the formula to calculate the horizontal resolution:

568 is the closest mod 4 value, so that’s why the result is rounded like that. Conclusion; our video’s resolution will be 568x352, AR of ~1.61. Now the black bars again: (800-568)/2 = 116 pixels on both sides.

Now, there are two things you need to remember from this step

• The resolution your video is going to be scaled to
• Amount of pixels for black bars