To modify a preset, you need to open the "Encoder Presets" window which can be found under the "Window" menu in Wirecast.
Be sure to select "QuickTime" from the "Output Format".
See the overview of this chapter for general information on the topic of encoder presets.
Changing the preset you are modifying
At the top of the window the "Encoder Preset" popup shows which encoder preset you are currently editing. Simply use the popup to select the preset you wish to edit.
Video Enabled
Wirecast offers the ability to optionally encode video for your broadcast. If you do not want your broadcast to include any video, simply uncheck "Video Enabled". This is the preferred method of producing audio-only broadcasts, as you are ensured that no video data is put into the stream (even "blank" video data can use bandwidth).
Encoder
This is the Encoder (sometimes called "Codec" or "Compressor") you wish to use.
Options
This is the Encoder specific options. Many encoders have options that are specific to the encoder that you can modify. It is beyond the scope of this documentation to describe all of the possible encoder options.
Depth
Some Encoders allow you to modify the Depth (or "Color Depth" or "Bits per Pixel") of the broadcast. Picking a higher color depth will result in larger output, but lesser quality color. It is beyond the scope of this document to describe all of the options an encoder may offer you here.
Width
This is the width of your resulting broadcast.
Height
This is the height of your resulting broadcast.
Quality
Many encoders allow you to adjust the Quality. Generally, encoders make a trade-off between Quality and Speed (how much CPU is used during encoding). Sometimes lower quality will also affect the bandwidth used.
NOTE: Some encoders may ignore this setting altogether.
Frames Per Second
This is the desired frame per second (FPS) of your broadcast. Note that the encoders try to stay "near" this value, and you are not guaranteed to always get the exact value you enter here.
Keyframe
If you imagine a movie as a set of images one after another, then each image is called a frame.
To compress your video data, most compressors take a frame and make it a "reference" or "key".
This key frame (Keyframe) is sent as part of the broadcast, and all of the data after that keyframe is relative to that Keyframe.
The benefit of this is that the compressor only needs to send what has changed since the last Keyframe.
The main drawback of this is that over time it's harder and harder for the compressor to make good "difference" information, especially if you have a lot of motion in the video. Another drawback is if your viewer happens to miss a Keyframe, the data that their player will show will not be comprehensible until the next Keyframe comes along.
You can control how often the encoder makes a new keyframe. Some encoders use this more as a "hint" as to when to send Keyframes.
Change this parameter to output more or fewer keyframes for your broadcast.
The more keyframes your broadcast has, the more bandwidth it will take (as less compression can occur). However, more keyframes means motion in your video stream is better supported.
Limit data rate to
You can request that the encoder limits the output to a specific rate.
NOTE: Some encoders use this as a "hint", not as an absolute value.