User`s guide

Setting Encoder Presets
Flash VP6
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Wirecast User Guide | 104730
capacity, and/or bandwidth. The Main profile is appropriate for general-purpose
applications of broadcast media, such as high-bandwidth Internet broadcasting.
10. Check Key Frame (optionally) and enter the number of frames. A movie is a
sequence of images and each image is called a frame. To compress video data,
most encoders take a frame and make it a reference (also known as a key). This
keyframe is sent as part of the broadcast, and all of the data after that keyframe is
relative to it. 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
becomes harder for the encoder to distinguish the frame-difference information,
especially if there is a lot of motion in the video. Another drawback is if your
viewer’s computer misses a keyframe, the video is distorted until the next keyframe
is sent. However, you can control how often the encoder makes a new keyframe by
setting the number of frames. The more keyframes you broadcast, the more
bandwidth required and less compression, but results in better quality video.
11. Check (optionally) the Timecode Every checkbox and enter the number of frames
between timecodes. Wirecast can generate timecodes embedded in the flash
stream. If a frames value of zero is entered, the timecode is never sent. Wirecast
sends metadata along with the frames. This data looks like an ONFi call. Various
timecodes and timestamps are also sent with the stream.
12. Check (optionally) the Audio Encoding (AAC) checkbox. When checked, the audio
for your broadcast is included. When unchecked, audio is absent. This is the
preferred method of producing video-only broadcasts because the presence of
silent audio uses bandwidth.
13. Select the number of channels: Mono or Stereo. Mono uses less bandwidth than
stereo, but stereo is more pleasing to the listener.
14. Select the audio bit rate, in Kbits (1000 bits) per second, from the Target Bit Rate
menu. This is the target bit rate of your audio. Higher numbers provide better
quality. The connection speed of your audience is a significant factor in
determining your target bit rate. The encoder compresses the audio to
approximate this target. However, at different times during your broadcast the bit
rate may be higher lower than the target rate. The total broadcast bit rate is a
function of video bit rate plus audio bit rate.
15. Select the audio sample rate, in kHz (1000 Hz) per second, from the Sample Rate
menu. This value specifies how many thousands of times per second to sample the
audio in the broadcast. Higher values provide better quality sound, but at greater
bandwidth.
16. Click Save to save your settings.
Flash VP6
To modify a Flash VP6 preset, follow these steps: