Choosing Your Encoding Settings


Authoring streaming media requires choosing certain encoding settings. The settings decisions you make are based on limitations of, among other things, the current state of software engineering, computer processing and the subjective nature of human hearing. Thankfully, how you make these encoding settings decisions is generally similar across all formats.

NOTE

Don't encode files that are already encoded. An encoded file sounds better if you begin with uncompressed source audio.


Any audio file that can be opened in a waveform editor can be saved (converted) as a QuickTime file.

Whether your source audio is spoken word, sound effects, or music, you must choose the bit rate, codec, and channel (mono or stereo) settings that are appropriate to your own and to your projected audience's needs prior to encoding. It's all about file size versus audio quality. Obviously you want your streaming audio file to sound as good as the available technology and bandwidth will allow. But you must also take steps to ensure that the stream reaches the user intact. Not everyone has broadband connectivity, so it's recommended that you choose the lowest bit rate setting you can get away with that still sounds acceptable. For instance: If you're authoring content that contains only a human voice (mono) speaking under normal conversational conditions, it isn't necessary to encode the streaming file at anything over 56Kbps (28Kbps is also recognizable). The voice will be heard and understood at 28- or 56Kbps, and you won't consume unnecessary bandwidth. If you're authoring encoded music files in stereo, however, listeners will have a more enjoyable sonic experience if you offer the streaming file at a higher bit rate (56Kbps minimum and above).

In these tutorials you'll use a 32Kbps (mono) encode setting for 56Kbps users and a 128Kbps (stereo) encode setting for DSL (or any other broadband format) users. It's possible to encode at higher bit rates but the sound quality isn't all that much better and, by keeping the high quality setting at 128Kbps, broadband users have headroom to use their connection for other tasks.

You'll be selecting the QDesign music codec for authoring your encoded files for these examples.

NOTE

If you find yourself authoring voice-only content for dial-up modem users, choose the Qualcomm PureVoice codec in the QuickTime encoding software menu. Advanced users might want to sample other codecs.


Because QuickTime Pro is relatively inexpensive, it only includes a basic version of QDesign's codec, limiting you to a maximum bit rate of 48Kbps for encoding files. That's not very high, and will not provide the much-touted near-CD audio quality that all formats promise. To use higher bit rate levels within QuickTime, download QDesign's QDMC Music Codec 2.1 Professional Edition ($399.00) from its Web site at www.qdesign.com. A less expensive option might be to acquire the 2.1 QDesign Pro software as part of a bundle of other encoding products, such as Cleaner Pro or Sorenson Broadcaster.

The bit rate limitation applies only to QuickTime Pro when authoring on-demand files. Software for live streaming (Sorenson or Cleaner) already includes the QDesign Music Codec 2.1 Professional Edition. This book uses the QDesign QDMC Music Codec 2.1.

QuickTime Stream Attributes (and Annotations)

Every QuickTime on-demand file or live stream contains a number of attributes, or pieces of information that the software uses to describe the content of the file. Filling out this information might seem time consuming, but it's good to do. It's frustrating to hear good music and have no idea who the performer is. Most of these attributes are referred to by the same names across different encoding tools, but a few exceptions exist. QuickTime's available attributes are outlined in the bulleted list below.

Live streaming QuickTime encoders include a configuration section for entering attribute information in only a limited number of fields. Authoring on-demand files, however, includes many additional descriptions. These additional descriptions are called annotations and are accessed by selecting Movie, Get Movie Properties (Macintosh: graphics/01icon05.gif+J, Windows: Ctrl+J) from within QuickTime Pro. This opens the Annotations window. You can view and edit existing values or add new ones through a simple interface. These changes can be preserved when you save the file or export it to another compression/ hinting combination. Unless noted otherwise, all fields are simple text fields.

  • Full Name A blank text field for entering the title of your stream. The QuickTime player displays this as the title of the player window. The Sorenson Broadcaster (see "Authoring a Live QuickTime Stream" later in this chapter) calls this attribute Title.

  • Author A blank text field for entering the author of the content of your stream.

  • Copyright A blank text field for entering copyright information for your stream.

    FezGuys' Tip

    graphics/01icon02.gif

    To quickly get a copyright symbol on the Macintosh, press Option+G; on Windows, press Alt+Ctrl+C.

  • Information A blank text field to enter a short description of your stream. The Sorenson Broadcaster calls this attribute Info. Tip: Consider putting a relevant URL here.

  • Comment A blank text field for other information about your stream. The Sorenson Broadcaster automatically inserts the name and version of itself into this attribute's field.

The Sorenson Broadcaster also has a program URL for including the URL to the Web site so that viewers can access your broadcast.

You can view a summary of attribute and annotation information during playback by selecting Window, Show Movie Info (Macintosh: graphics/01icon05.gif+I, Windows: Ctrl+I).



Streaming Audio. The FezGuys' Guide
Streaming Audio: The FezGuys Guide
ISBN: B000H2N1T8
EAN: N/A
Year: 2001
Pages: 119

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