The Problem

Recently I was working on a project that required a combination of an animated introduction with music and alternating sections with a video of the host talking and a Captivate movie with the host’s voice synced to the movie. We had never combined Captivate SWFs with audio and Flash SWFs with audio in the same project, and we found it difficult to match the audio quality of the final SWFs. No matter what compressions we tried, the Captivate files sounded worse. Because we were short on time, we saved the Captivate files as FLAs and exported the final SWFs from Flash so that the sound quality would match.

The solution worked, but I was left wondering if there was a way to match the sound quality of audio output in Flash and Captivate without exporting to Flash.

The Research

I searched the web for help answering this question. The first piece of information I found was that a non-critical patch for audio degradation had been released for Captivate 4 in May 2009. Non-critical patches do not get downloaded as an automatic update—you have to go to Help > Updates and download it yourself. I did this immediately because it not only improves the audio, but it fixes a memory leak, compile problems and more.

The patch helped but it didn’t completely solve the quality discrepancies between Captivate and Flash.  My next stop was Mark Siegrist’s elearninglive.com blog. In July 2008, Siegrist started blogging about Captivate audio output. He tests the effects or the three configurable audio parameters on the audio quality and files sizes. The series is missing the final post summarizing the results and recommending settings to use for the best file size-to-quality ratio, but the existing posts are incredibly informative and contain examples that you can listen to and compare. I have listed the posts below.

• Captivate Audio Output Settings Comparison – Part One – Encoding Bitrate
• Captivate Audio Output Settings Comparison – Part Two – Encoding Frequency
• Captivate Audio Output Settings Comparison – Part Three – Encoding Speed

This series of posts allowed me to begin testing right away. I decided to test whether or not importing different audio formats (WAVs and MP3s) at different qualities would help me find a way to match the audio in Captivate to the audio in Flash.

The Testing

I imported a variety of MP3 files into both Captivate and Flash, trying to match the audio quality to the published SWFs. The MP3s included 128kbps/44.10khz,  64kbps/44.10khz, 48kbps/44.10khz and 48kbps/20.50khz 16-bit files (Captivate only accepts 8-bit and 16-bit audio files). Even the 128kbps/44.10khz file in Captivate had slightly more static compared to the 48kbps/44.10khz file in Flash, with publish settings in each program set to match those of the native files.

Although WAVs imported into Captivate get converted to MP3s when you publish to a SWF, I decided to try importing a 128kbps/44.10khz 16-bit WAV file into Captivate to see if I would get better results than the MP3. The results were the same.

The Solution

It’s best not to mix Captivate published SWFs in the same project as Flash published SWFs. We are often able to get around this problem by having a Flash wrapper handle all audio for the course, though this creates difficulties when the Captivate and audio need to be synced. In cases where audio needs to be synced, the quickest and easiest solution is to save your Captivate file as an FLA and publish in Flash.

But don’t get the wrong idea—just because these solutions worked for us doesn’t mean that Captivate has poor audio compression. That is not the case at all. As you can hear in Siegrist’s posts, you can get very good quality audio in Captivate published SWFs.

The Summary

I could not find a way to match the audio quality of SWFs published from Captivate and SWFs published from Flash, although I was able to improve the Captivate results by downloading the patch. I also learned from Siegrist’s posts that the best file size-to-quality ratio can be achieved using 48kbps/44.10khz compression with an encoding speed of 8.

The question remains—is Captivate audio compressed the same way as Flash audio? I could not find documentation from Adobe that would help me answer this question, but my tests lead me to believe that audio compression for the two programs is not the same. If you have any information you can share with me on this topic, please leave a comment below.

Tags: audio, Captivate

This entry was posted on Wednesday, October 21st, 2009 at 12:48 pm and is filed under Developer. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.