Constant vs Variable Bit Rate in Ogg Vorbis

Special Interest Groups Making Music
1

I’m using Audacity 2.0.6 on Mac OS X Yosemite and exporting audio to MP3 and Ogg for distribution in an HTML5 media player. After doing this I discovered a problem with synchronization. Most browsers now support MP3, but if I export to MP3 using variable bit rate encoding the timing gets out of sync if the user scrubs ahead or back. I experimented with a wide variety of MP3 output settings and found that exporting to MP3 using a constant bit rate eliminates this problem. Here’s a test page:
http://terrillthompson.com/tests/media

The problem is: Firefox does not yet support MP3, so I must also deliver the audio in Ogg Vorbis format, which Firefox does support. However, there doesn’t seem to be a comparable option, within Audacity anyway, to export to a constant bit rate Ogg Vorbis file. Does Ogg Vorbis support constant bit rate, and if so, is it possible to attain that via Audacity? (I assume Audacity’s Ogg Vorbis functionality is the same in Windows and Linux as it is in Mac, but if not I’m willing to try another OS).

If Audacity doesn’t provide this capability, is there another tool I could use to convert from WAV or AIF to Ogg Vorbis with a full set of options?

2

Ogg Vorbis is VBR by design (so as to achieve best sound quality for the specified bit rate).

With your test page, the VBR is within 1 second for me (Firefox on Linux), which I guess would be perfectly adequate for most purposes.
The good news is that HTML5 media support is gradually improving across different platforms and browsers.

3

Thanks @Steve. I’m actually seeing a bigger discrepancy than that in my tests with Firefox. After scrubbing forward and back I’m off by up to five seconds in both Mac and Windows. This poses huge problems for timed text applications (e.g., adding karaoke-style lyrics to accompany the media).

4

Perhaps better to use a video format for such applications (until such time as the technology improves).

5

Opus seems to work as a CBR alternative to Vorbis, and Firefox supports it. I haven’t figured out how to export to Opus using Audacity—presumably I can do that with an external program?

Meanwhile, I exported my test file to Opus using audio.online-convert.com and that seems to have fixed the problem on my test page.

6

Yes I believe it can, though I don’t know off the top of my head what the necessary command line switches will be.