Playing Video Files with AC-3

by Matt

Eric wants to know how he can play video files with AC-3 audio. For those of you who don’t know what AC-3 is, it’s the technical name for Dolby Digital, which is an audio format that can contain up to six discreet channels of digital sound. It’s a highly optimized format, meaning you can store a large amount of sound data in a (relatively) small amount of disk space. Most commercial DVDs have AC-3 soundtracks for surround sound systems.

While Apple’s DVD Player can handle AC-3 files in DVDs, it cannot play files you download from the internet. If you try opening the file in QuickTime Player, the file will open and the video will play, but you won’t hear any sound. So how do you play those types of files? Well, there are three ways we can handle this: install Perian, use VLC, or convert the file. Let’s look at each.

Using Perian

I’ve covered installing Perian before, so I won’t cover it in depth here. Basically, Perian is a combination of one System Preference and several QuickTime components. These components are plug-ins that add functionality to the QuickTime Player, including the ability to play files with AC-3 audio. Once installed, you should be able re-open QuickTime Player and hear the sound from these movies.

While Perian is wonderful, it’s not perfect. At the time of this writing, the current version of Perian is 1.1.3, and still there are some problems getting AC-3 audio to play via Perian. In Eric’s case, he already had Perian installed, but the sound still would not play. It is likely that the video file is slightly corrupted or the audio encoder used to create the file does not encode the AC-3 audio in a 100% compatible manner. Thus, the next option is VLC.

Using VLC

Just as I did with Perian, I have previously covered VLC, so please read that article if you’d like to know more about its installation. VLC (short for VideoLAN Client) is an application that is an alternative to QuickTime Player. It does not rely on the QuickTime components from Apple or Perian to play audio and video; instead, it uses its own video rendering engine (based off many open source codecs). Because of this, some files that will not play properly with Perian installed will play properly in VLC (and vice versa).

To try playing a file in VLC, all you have to do is open the file in the application. If it can play the video, you’ll see it on the screen. If it can play the audio, you’ll hear it. If your file is so finicky that even VLC cannot play it, our last best option is to convert the file so that it has an audio format that these programs can recognize.

Converting the File with Handbrake

My first post on this website was a long tutorial on how to convert DVDs to work on your iPod, iPhone, or Apple TV. The great thing about Handbrake is that it now supports coverting any video file, not just DVDs. That means we can convert files with the pesky AC-3 audio. If you have not used Handbrake before, please read my post, as this will provide the basis for doing the job.

In addition to the post, there are a couple of things you should keep in mind:

  1. When you want to select a file to convert in Handbrake, this time, you’ll just want to choose the file with the AC-3 audio rather than a DVD.
  2. While I previously advocated using the “Universal” preset, that is not necessary here if your only goal is to get the video to play on your computer. I’d still recommend it if you think you want to play the file on your iPod/iPhone/Apple TV, but if it’s only for your computer, you can choose the “QuickTime” preset from the list of “Apple” presets.
  3. The other thing you may have to change is under the Audio & Subtitles tab. Take a look at your audio sources (there probably will only be one track listed, and it will be AC-3). Make sure under “Audio Codec” you have selected “AAC (faac)” but not “AC3 Passthru.” If you do a pass-through, that means the audio will remain the same; we want it to be converted to AAC.
  4. Once those settings are verified you can begin the conversion process. When it ends, you should have a video file that plays in both QuickTime Player and VLC!

Did these tips work for you? Do you have a better way of handling pesky AC-3 files? Any tricks to make Perian or VLC handle problem files? Share your thoughts in the comments section.

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