QVidium QVSD - Manual (Page 41)

User‟s Manual v.3 QVidium
®
QVSD H.264 SD Video Codec™
Copyright 2011 QVidium
®
Technologies, Inc.Page 41 of 53
12
Appendices
12.1 Appendix A: Encoder Configuration Parameters
This section explains the parameters related to the analog input signals and encoding
settings and how they relate to the operation of the encoder and error correction and
network transport setup.
Video Encoding Bit Rate: Total peak stream bit rate for Variable Bit Rate (VBR) video
encoding. The resulting transport stream bit rate is the sum of the bit rates of the video
program, audio program and program stream information. The video bit rate is specified
in bits per second and can range from 128 Kbps for CIF resolution to 19 Mbps for
720x480 (NTSC) or 720x576 (PAL) standard definition resolutions, or can range from 4
Mbps to 19 Mbps for high definition video resolutions. The higher the bit rate, the better
the video quality.
Audio Bit Rate (compressed): The audio bit rate determines encoding audio quality and
allows you to trade off audio throughput for quality. The audio bit rate can be set to one of
64,000, 128,000, 192,000, 256,000 or 384,000 bits per second. Increasing the audio
bitrate, up to a maximum value of 384 Kbps increases the audio fidelity. Regardless of the
audio signal level on either channel, selecting an audio bitrate of 64 Kbps or higher will
always force the encoder to send 2 channels of audio (stereo audio). Each audio channel
uses one-half of the selected audio bitrate. The H.264 SD Video Codec™ encodes audio
using either MPEG-1 Layer II encoding, MPEG2 AAC, or MPEG4 AAC audio encoding.
For minimizing the audio bitrate, we provide the option of setting the number of audio
channels to 1 and the audio bitrate to 16 Kbps or 32 Kbps. Do not use an audio bitrate
less than 64 Kbps unless you set the number of audio channels to 1. Even then, setting the
number of audio channels to 1 has the potential to cause unexpected halting of the
encoder. So, please be aware that this option may impact the reliability of the encoder.
Audio Sampling Rate (Hz): The audio sampling rate specifies the clock rate for capturing
and digitizing the incoming analog audio signal. Because of anti-aliasing filtering, the
maximum audio frequency that can be digitized is limited to a frequency of about 1/3 to
1/2 of the audio sampling rate. Internal anti-aliasing filters severely attenuate audio
signals above a frequency of about 1/3 of the sampling rate. Thus, for a standard music
CD rate of 44.1 KHz, the maximum audio frequency that the encoder can pass is about
14.7 KHz. The valid selectable audio sampling clock rates are 32 KHz, 44.1 KHz, and 48
KHz.
SDI formatting requires that the audio sampling rate be fixed at 48 KHz, so if sending to
another codec with SDI output, please use 48 KHz sample rate.
Video Frame Rate (Full Frame Rate and fractions thereof): Select Full Frame Rate for
normal video. This will encode the video signal at 29.97 frames per second for NTSC and