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Ok, so you want the best quality, smallest sized AVI files from BB FlashBack. In this article we'll try to give you a good understanding of the main factors that determine file size and quality:
- The frame rate of the movie.
- Whether it has sound, and how that is encoded.
- The content of the movie - what you've recorded.
- The codec used to compress the movie.
It's easy enough to understand how the frame rate, sound and content of the movie affect the file size, so we'll tackle those first. Figuring the best codec to use can be a bit more involved, so we'll build up to that. |
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| Frame rates |
The 'frame rate' is the number of frames per second displayed by the movie. Higher frame rates mean smoother movement during playback, but all these frames need to be stored in the AVI file, so it also means bigger files.
BB FlashBack lets you set the frame rate on the 'Video' tab of the AVI Export Options window.
Like it says, higher frame rates = smoother movements, but bigger AVI files.
BB FlashBack's default frame rate is 25 frames per second. 25 fps looks pretty good - similar to what you'd see on your TV or at a movie theater, so if you care more about file size than smooth motion, you could reduce the frame rate to get smaller AVI files and still have good quality playback. |
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| Sound |
If your movie was recorded with sound, this sound also needs to be stored in the AVI, and if this movie lasts for a few minutes, this can add megabytes onto the same movie recorded without sound. As ever with this sort of thing, higher quality sound means bigger files. BB FlashBack lets you set the sound quality on the Audio tab of the AVI export window.
There's two sets of controls that control the sound quality and, therefore, the AVI file size: the Format controls and the Compression controls.
The Format setting should be pretty self explanatory: select lower quality for smaller files.
You should normally keep the 'Use MP3 compression' box checked - if you don't, you'll find the AVI file you export grows dramatically, if it contains sound. You've got a few compression quality settings to choose from. As usual, higher quality means bigger files.
If Sound quality isn't important to you, try the lowest quality settings for format and compression - this will probably do the job fine. If it is important, you'll need to play around with these settings to find the best balance of quality and file size for you. |
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| Why what you record matters more than how long you record it for.. |
Here's something that people can find difficult to understand: when it comes to file size, what you record is often a lot more important than the duration of the recording. That's because AVI files store only the changes to your screen.
Say you record your screen for an hour but just leave the PC alone in this time, with all windows hidden. Nothing much changes on screen (if you've disabled the screensaver). Any AVI exported from that recording is unlikely to break a megabyte.
On the other hand, if you're exporting a recording of a screen that has some video being played back, a game or some other animation (on a web page, for example), you're going to be talking multi-megabytes, even if the movie lasts only 30 seconds. This is because those videos and animations mean lots of big changes happening to the screen, at a fast rate. All these changes need to be stored in the AVI file, and that means bigger files.
But keep on reading - if you know something about codecs, you'll be better equipped to squeeze these AVI files down to size. |
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| About codecs |
When you export an AVI from BB FlashBack, you have to choose a codec. Here's a reminder of what that codec selection window looks like:
A codec is a small program on your PC that compresses and uncompresses movie footage, It compresses the footage so it can be crunched down into (hopefully) a reasonable sized AVI file. It uncompresses the footage back out of the AVI file so it can be displayed by your movie player. You need codecs to do this job because movie files get *huge* if every frame is stored with no compression.
Different codecs have different ways of compressing footage, so exporting the same FlashBack movie with different codecs will make different size and quality AVI files. |
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| Choosing a codec |
There are lots of codecs out there that you can download for free, so why not search around, find a one that makes nice small movies, export your FlashBack files with it and put the AVIs onto your website for everyone to see? There’s a good reason: you often need that same codec installed to play the movie in Windows Media Player. The Media Player needs to understand how this movie was compressed, so it can uncompress and play it properly. If someone downloads your AVI file and hasn't installed the codec you used to encode it, Windows Media Player is unlikely to play it back.
Obviously it’s a pain for people to download and install a codec first, before viewing your movie, so what can you do? One option is to use a default Windows codec. These are codecs that are installed on pretty much all Windows PCs, so an AVI exported using them is very likely to play back on the big majority of PCs. Here are the default codecs:
- Microsoft Video 1
- Cinepak
- Indeo v3, 4, 5
- Full frames (uncompressed)
These aren’t the best codecs in town, but they get the job done. The exception to this is ‘Full frames (uncompressed)’ – you should only use this if you need to edit the AVI in some other editing package, because it creates *huge* files.
Of the above, we’ve found that Microsoft Video 1 often gives the best balance of file size and quality for screen recordings.
Non-default, third-party codecs can give much better results. Of those we’ve tested, we rated Xvid best (get it free at www.divxmovies.com), but if you decide to use it, remember the caveat above – you’ll find that some people that can’t play back Xvid encoded AVIs in their default movie player. |
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| More on playing AVIs encoded with third-party codecs |
| Just in case you ever get confused on this point: not all video players are (intentionally) dumb like Windows Media Player. Some movie players, like VLC Player for example, have an in-built understanding of lots of codecs, so they can play back movies encoded with them without needing the codec itself to be installed. But the default movie player for many people is going to be Windows Media Player, so if you want these guys to be able to play your AVIs, you should play safe and stick to the default codecs above. |
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| Another option for making good, small movies: WMV |
If you really need your AVIs to play back on as many PCs as possible, and the default Windows codecs just aren’t cutting it in terms of file size and quality, a better option might be exporting to Windows Media Video format (.wmv files). BB FlashBack (not the Express edition) can do this as well, as long as Windows Media Player 9 or newer is installed.
There are a few flavours of WMV to try out. The main two to be aware of are Windows Media Video 9 and Windows Media Video 9 Screen. The ‘9’ codec gives pretty good results all round, particularly with moving video and animations. The ‘screen’ codec can give terrific results if your movie just contains ‘normal’ applications like MS Word, Outlook etc, but it’s really bad at reproducing photo-type images or subtle shades of colour.
So far, so good, but we’d better warn you: although WMV files can be played back on a big percentage of PCs, those that have an older version of Windows Media Player may hit problems. There’s a summary of how different versions of Media Player deal with the various flavours of WMV in the BB FlashBack help file – see the “WMV codec compatibility” topic. |
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| Final advice on codecs and AVI export |
A lot depends on what you’ve recorded, so as much as we’d love to, there’s no way we can say “this is the best codec to use – period”. If you really want the highest quality, smallest AVI movies, you’ll need to try exporting to a few different codecs, and experimenting with their settings to see what happens. And if you can, you should always try and test your AVIs on a PC other than the one used to export it – this can often show up any problems in encoding.
We hope you’ve got a good appreciation of what affects AVI file size and quality, the factors in choosing a codec and some recommendations to fall back on. The rest is down to you! |
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