Matrix Elements VB-800 Manual do Utilizador descarregar pdf (Página 32)

Chapter 3. Advanced streaming using the command line

cropright=

This option allows to crop the right part of the source video. The argument is the X coordinate of the ﬁrst column to be

cropped.

scale=

This option allows the give the ratio from which the video should be rescaled while being transcoded. This option can be

particularly useful to help reduce the bitrate of a stream.

width=

This options allows to give the width of the transcoded video in pixels.

height

This options allows to give the height of the transcoded video, in pixels.

acodec=

This options allows to specify the codec the audio tracks of the input stream should be transcoded to.

List of available codecs can be found on the streaming features page (/streaming/features.html).

ab=

This option allows to set the bitrate of the transcoded audio stream, in kbit/s

aenc=

This allows to set the encoder to use to encode the audio stream. Available options are:

• ffmpeg: this is the libavcodec encoding module. It handles a large variety of different codecs (the list can be found on the

streaming features page (/streaming/features.html).

• vorbis. This module uses the vorbis encoder from the Xiph.org project. Vorbis is a free, open, license-free lossy audio

codec.

Item options are: quality=<quality level> allows to use VBR (variable bitrate) encoding instead of the default CBR

(constant bitrate), and to set the quality level (between 1 and 10, higher is better), max-bitrate=<bitrate in kbit/s> allows

to set the maximum bitrate, for vbr encoding, min-bitrate=<bitrate in kbit/s> allows to set the minimum bitrate, for vbr

encoding, cbr allows to force cbr encoding.

• speex. This module uses the speex encoder from the Xiph.org project. Speex is a lossy audio codec, best ﬁt for very low

bitrates (around 10 kbit/s) and particularly video conference.

samplerate=

This option allows to set the samplerate of the transcoded audio stream, in Hz. Reducing the samplerate is be a way to

lower the bitrate of the resulting audio stream.

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Matrix Elements VB-800 Manual do Utilizador Página 32