User guide

DivX 10
40
DivX, LLC User Guide
AUDIO
DivX is a video codec. As such, it does not handle audio in any way
and we will not cover the very broad topic of audio in detail. Most
likely, you will want audio with your DivX video, so we will briefly cover
a few important points.
1 - There are many audio formats and codecs that can be used in
combination with an AVI container, each with different properties
and features. DivX-encoded AVI files generally use Constant Bitrate
MPEG1-Layer 3 Audio, or CBR MP3 for short. CBR MP3 is the
recommended audio format for DivX video and has a number
of benefits:
• MP3 audio is supported natively by most operating systems
• MP3 audio is supported by DivX Certified hardware players
• CBR MP3 audio is least likely to introduce de-synchronization
between audio and video.
The MP3 codec distributed with Windows is the Fraunhofer IIS
MPEG Layer-3 Codec (advanced). This codec is capable of decoding
high-bitrate MP3 format audio but is limited to low-bitrate encoding.
VirtualDub works only with audio codecs designed for Microsoft’s
Audio Compression Manager, or ACM, and thus you will need
to install an ACM MP3 encoder.
As a rough guide: 128 kbps is generally considered close to CD
quality when encoding to CBR MP3, but bitrates 112 kbps and up
are generally acceptable for stereo sound. Halve the bitrates for
mono sound.
2 - Audio contained in an AVI file must be correctly interleaved for
stable playback performance—particularly when content is to be
stored on optical media (such as CD-R or DVD-R), or other media
with high seek times.
Consider this AVI container with one video and one audio stream: