Qvidium QVSD Manuel d'utilisateur télécharger pdf (Page 18)

User‟s Manual v.3 QVidium

QVSD H.264 SD Video Codec™

Technologies, Inc.Page 18 of 53

The analog audio input, by default, accepts a maximum input voltage of about ±400 mV

peak

. Above

this level, the input circuitry limits any additional signal levels by clipping the digitized signal to this

peak value. This level is close to the standard consumer analog level of ±447 mV

peak

, and

significantly less than professional peak audio voltage levels (1.737 V

peak

US and 2.192 V

peak

German). In order to accommodate various consumer and professional analog audio input

sources, you can select from among 3 preset standard audio signal levels, Consumer,

Professional US, Professional Europe. You can also manually adjust the attenuation of the audio

input.

3.3

Dynamically Changing the Video Encoding Bitrate

Once encoding has begun, you can instantaneously vary the video encoding bitrate. This can be

useful when connecting to wireless modems and other network connections with limited, but

unpredictable, time-varying throughput characteristics. As described in this section, we provide

several mechanisms for dynamically adjusting the video encoding bitrate. In particular, this can

allow a modem to feed back link throughput constraints directly to the encoder to dynamically

optimize video quality over such bandwidth-constrained networking links.

3.3.1

URL Control

There are 2 URLs, one to get the current video bitrate and a second url to set the video bitrate.

These URLs return plain text (no HTML) to simplify parsing. The "Encoder->Bitrate" link in the

web UI allows you to set the video bitrate with a browser.

/cgi-bin/encoder_bitrate2.cgi: Gets the current video bitrate. Returns

VIDEO_BITRATE=xxxxxxx, where xxxxxxx is the current bitrate.

/cgi-bin/encoder_bitrate2.cgi?VIDEO_BITRATE=xxxxxxx: Sets the video bitrate where xxxxxxx

is the desired bitrate. Returns VIDEO_BITRATE=xxxxxxx where xxxxxxx is the bitrate that was

set. The maximum video bitrate is 25000000.

Examples of using the wget command. The initial bitrate was 23Mbps.

$ wget -q -O - http://root:[email protected]/cgi-bin/encoder_bitrate2.cgi

VIDEO_BITRATE=23000000

$ wget -q -O - http://root:[email protected]/cgi-bin/encoder_bitrate2.cgi?VIDEO_BITRATE=9000000

VIDEO_BITRATE=9000000

$ wget -q -O - http://root:[email protected]/cgi-bin/encoder_bitrate2.cgi

VIDEO_BITRATE=9000000

$ wget -q -O - http://root:[email protected]/cgi-bin/encoder_bitrate2.cgi?VIDEO_BITRATE=500000000

VIDEO_BITRATE=25000000

3.3.2

Command-line Control

The program, /qvidium/qvctrl, allows you to communicate with the encoder via a command-line

interface, such as telnet, ssh, or the RS-232 Console port. The first argument is always

/dev/qvencode, The second argument is "get_videobitrate" or "set_videobitrate xxxxxx" where

xxxxxx is the bitrate would want to set (max bitrate is 25000000). The command always returns

VIDEO_BITRATE=xxxxxxx where xxxxxx is the current bitrate. Here are examples:

[QVSD.qvidium.com]$ /qvidium/qvctrl /dev/qvencode "get_videobitrate"

VIDEO_BITRATE=4000000

[QVSD.qvidium.com]$ /qvidium/qvctrl /dev/qvencode "set_videobitrate 2000000"

VIDEO_BITRATE=2000000

[QVSD.qvidium.com]$ /qvidium/qvctrl /dev/qvencode "set_videobitrate 8000000"

VIDEO_BITRATE=8000000

1 2 ... 13 14 15 16 17 18 19 20 21 22 23 ... 52 53

Commentaires sur ces manuels

Pas de commentaire

Qvidium QVSD Manuel d'utilisateur Page 18

Commentaires sur ces manuels

Produits connexes et manuels pour Équipement Qvidium QVSD