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Captivate Audio Output Settings – Part Three – Encoding Speed

Mark — Sat, 26 Jul 2008 15:59:29 +0000

This is part three of the testing, where I’ll focus on the encoding speed setting and its effect on filesize and audio quality, in reference to voiceover audio.

Published SWF Files

Filesize Comparison

Summary

To my ears, the encoding speed set to 0 sounds the best. And amazingly, it yields the lowest filesize. So far, it seems that a setting of 48-44-0 is the best for voiceover-based Captivate movies. I’ll do some further testing this time will large, real movies that contain slide data and a lot of audio (including some music), for the next post.

Captivate Audio Output Settings Comparison – Part Two – Encoding Frequency

Mark — Sat, 26 Jul 2008 15:33:48 +0000

This is part two of a series of articles written with the express purpose of finding the best filesize-to-quality ratio for publishing voiceover audio out of Captivate. Part One can be found here. At the end of the series I’ll provide my thoughts/opinions, followed up by a tabular summary of the facts. And, of course, a recommended setting.

More information about the testing methodology can be found in part one of the series.

Encoding Frequency

There are three encoding frequency settings available in Captivate:

: Captivate Encoding Frequency Options

For this test, I settled on the following settings for each and simply changed the encoding frequency.

Encoding Bitrate: 48kbps
Encoding Speed: 5 (the default)

As with the last test, each swf was published with the three settings shown on the slide:

Published SWF Files

Published File Size Comparison

As you can see, no matter which encoding frequency is selected the published swf is roughly the same file size. However, if you listen closely you’ll hear that the clarity is slightly better when using the 44.10khz setting. This is not so evident in comparison to the 22khz sample, but definitely if you first listen to the 11khz and then the 44khz. So, it seems that it makes no sense, based on my little test here, to ever drop the encoding frequency to below the default setting of 44khz. I guess I’ll have to try with a larger audio file to see if that makes a difference? Or should I redo these tests with a source audio file that has a short musical intro followed by voiceover audio? Perhaps that would yield more definitive results? If anyone with in-depth knowledge of the meanings behind these settings reads this please comment and/or email me if you can explain some of this stuff better so I can include it here.

Summary

For years I’ve always seemed to settle on using an encoding bitrate of 48kbps. Not due to any real testing other than some quick, under-tight-deadline-pressure, testing. To my ears, this comparison seems to confirm that 48kbps is the proper setting for voiceover audio as it yields good clarity as well as good file size. Listen to the 128kbps sample, followed immediately by the 48kbps sample, and then the 32kbps sample. You’ll hear a definite difference between the three, but the 48kbps is still very good. The 32kbps is somewhat muffled. I don’t think any students/users would know the difference between the upper two, but the 32kbps is muffled enough that it would bother me over time.

In the next part of this series I’ll demonstrate how varying the encoding speed setting effects things.

Captivate Audio Output Settings Comparison – Part One – Encoding Bitrate

Mark — Fri, 25 Jul 2008 04:14:16 +0000

I’ve been wanting to do this for a few years but have never had the time. Goal: determine exactly what the optimal audio output settings in Captivate are for voiceover audio, which is 99% of the audio I use in Captivate (and I could care less if background/intro music is not fm quality!). I’m currently working on a project in which I really need to keep file size down, and after searching for a definitive audio settings comparison chart on this topic I couldn’t find one…so, here goes.

Comparison Details

While I’m no scientist, I think I adhered to a logical way of approaching this. I of course used the same machine to publish each clip, I used the same exact .cp file for each file (I simply went into the Publish window’s Audio settings and decreased the encoding bitrate, then double-clicked on the single text caption in the movie (residing on the first slide (of two) and set to display throughout project), and then published.

For the audio file, I used the same audio clip that I got from a public domain audio book website. I simply downloaded the full clip, in .ogg format, from the page above and then opened in Audacity to export the first 8 to 10 seconds of it. I exported to .wav format. I of course used the same exact audio file for each published output (again – I used the same exact .cp file repeatedly for each test).

Here are the results for you to compare with your ears:

And, the file sizes:

Captivate Audio Settings File Size Comparison

No, the 16 and 24 bit version filesizes being higher than the higher-quality ones is not a typo. At first I was so surprised that I went and re-checked and re-published. So basically from what I can see there is no point in ever going below 32kbps as you’re gaining filesize and losing quality.

Where I’ll Go From Here

Obviously encoding bitrate is just one of the 3 parameters that can be configured, with the other two being encoding frequency and encoding speed. I will be following this post with some new tests that compare those settings. Eventually, I hope to compile a definitive table and a final recommendation for exactly what settings in Captivate deliver the absolute best ‘value’ in terms of filesize-to-quality ratio. Keep in mind that I am concerned strictly with voiceover audio. I would assume that is what anyone else would care about when it comes to Captivate as well.

Please leave a comment if you have suggestions, or know of an unbiased, definitive comparison that perhaps I missed in my search, or if you have any tips for how I should approach the next batch of tests.

UPDATE: I’ve continued on with the testing. Here is a link to Part Two.