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• Bit Rate pop-up menu: Choose the bit rate to use for the output audio. Choices are
64 kbps, 128 kbps, 192 kbps, 224 kbps, and 384 kbps. Higher bit rates produce higher
quality audio, but they also produce larger output files.
Note: The 224 kbps and 384 kbps settings are not available when Channels is set to
Mono.
About System and Elementary Streams
You can use Compressor to create system or elementary MPEG-1 streams.
System Streams
System streams, also known as multiplexed streams, combine the video and audio
components into the same file. This type of stream is most often used in web applications.
Compressor automatically creates a system stream when you enable both the Video and
Audio tabs in the same setting.
Elementary Streams
With elementary streams, there are separate files for the video and audio components.
Elementary streams are required by some applications.
Compressor automatically creates an elementary stream when only the Video or Audio
tab is enabled, but not both. To create elementary streams of both the video and the
audio, you must use two settings—one with the Video tab enabled using the file extension
of .m1v and a second with the Audio tab enabled using the file extension of .m1a.
MPEG-1 Transcoding Workflow
This section gives step-by-step instructions for setting your MPEG-1 attributes prior to
creating MPEG-1 output files with Compressor. Make your MPEG-1 settings from the
MPEG1 Encoder pane by either modifying an existing setting or creating a new setting.
See the following for common settings with the MPEG-1 output file format.
Encoding for the Web
Use the following settings when encoding MPEG-1 system streams for the web.
Video tab:
• Frame rate: Automatic
• Purpose: Web
• Bit rate: As low as you can set it and get acceptable picture quality
Audio tab:
• Sample rate: 44.1 kHz
186 Chapter 17 Creating MPEG-1 Output Files