HTML5 Audio Sync Tests

These test files demonstrate that variable bit rate (VBR) MP3 audio files get out of sync if the user scrubs forward or backward. For additional information see my blog post Constant vs Variable Bit Rate MP3 Encoding and Timed Text.

Audio with Variable Bit Rate MP3 (encoded using Audacity)

• media.currentTime:
• currentTime reformatted:

Audio with Variable Bit Rate Ogg Vorbis (encoded using Audacity)

• media.currentTime:
• currentTime reformatted:

Audio with Constant Bit Rate MP3 (encoded using Audacity)

• media.currentTime:
• currentTime reformatted:

Audio with Variable Bit Rate MP3 (encoded using MediaHuman)

• media.currentTime:
• currentTime reformatted:

Observations

Tested with the following browsers:

• Firefox 35
• Chrome 40
• Safari 7.1.2 (in Mac OS X 10.10.1)
• Opera 26.0
• Internet Explorer 11

1. In all browsers, all mixes play reliably from start to finish if you don't scrub.
2. In all browsers, if you scrub back and forth using the slider, the variable bit rate MP3 audio mixes will eventually get out of sync (the vocals indicate the correct media time, but the time reported by the player is off).
3. In all browsers, this media timing problem does not seem to happen with the constant bit rate mix, nor with the Ogg Vorbis mix (for browsers that support it).

For additional observations see my blog post.