Difference between revisions of "Audio Commentary"

Revision as of 16:13, 16 July 2007

Introduction

SDA allows audio commentary in the form of a secondary audio track in an existing H.264/AAC audio/video stream. In other words, one video stream and two audio streams in one MP4 container. It's about time, isn't it? The main reason it took so long is because QuickTime 7 doesn't handle multiple audio tracks properly. As it is now, QuickTime 7 will play all audio tracks at the same time, not very pleasant to the ears. The solution is simple: disable the secondary audio track so that QuickTime won't play it, while all other decent media players will still have the option.

Multiple audio tracks in the AVI container is still not allowed. Windows Media Player also happens to play all audio tracks at the same time.

Record yourself

Editor's note: someone else with experience on how to get setup with a mic, etc, will have to write this. Also, some tips on what people generally like to hear, stuff like that.

For now, you're on your own.

Mixing / Compressing / Muxing the audio

Once you've recorded your commentary, you may want to consider mixing it with the gameplay audio, but at a low volume so that we can still hear you. Audacity, a free sound editor is capable of doing this.

Load your finished wav file in MeGUI for compression. SDA is fairly strict about choosing the bitrate corresponding to whichever quality version you're encoding. However, with audio commentary it's quite lax; do whatever sounds good. Commentary with just the voice and no gameplay audio mixed in can go as low as 32 kbps and still sound good. Also, don't bother with adding commentary for the LQ version.

Use MeGUI again to add the audio commentary. Notice the audio section let's you pick only two audio streams at a time. To add more, first save the file with the two streams. Load that into the Video Input field, it will recognize that there's already audio tracks inside. Then just repeat like before. Don't get carried away, though, more audio tracks equals a bigger filesize. Consider lowering the bitrate of the commentary tracks if you have to. To make it easier for you later on, be consistent with which stream becomes input #1 and which stream becomes input #2. I suggest putting the gameplay audio as input #1.

Tip: YAMB can also mux files for you and has other useful features.

Disabling the audio commentary for QuickTime 7

You absolutely must do this, even if it may be tedious to do so. Be sure to double-check your work in QuickTime when you're done.

• First, you'll need to download and extract Dumpster.
• Drag the MP4 file over dumpster.exe to load the program.
• Double-click the line with 'moov'.
• You'll see three 'trak' items. The first is probably the video track, the third is probably your second audio track. Double-click on that third 'trak' item.
• Double-click 'tkhd'.
• Select the line with 'flags'

• Change $000001 into $000000
• Click Apply.

Warning: If you do any re-muxing of a file that you've dumpster'ed, it may reset the flag to $000001.

Congrats, you're all done.

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