Dolby E Transcode
A Dolby E encoded audio input can be decoded and subsequently re-encoded using a different coding algorithm if
a /VP/SWO/DOLBYE/DEC license is available.
The following parameters configure the audio decoder:
Center mix level
Indicates the downmix level when there is no centre speaker. This is applied to left and
right channels only.
Surround mix level
Surround downmix level for the front left and right channels when consumer has no
surround speakers.
Dolby Surround mode
Flags if a two channel encoded stream contains information for a Dolby Pro-logic decode
(Lt/Rt)
Audio production information
exists
This indicates whether the Mixing Level and Room Type parameters exist within the bit-
stream.
Mixing level
Indicates the acoustic sound pressure level of the dialogue level during the final audio
mixing session.
Room type
Type and calibration of the mixing room used for the final audio mixing session.
Copyright flag
Indicates if the material is copyright protected
Original bitstream flag
Indicates if source is the original or a copy
Enable extended bitstream
information
Flags if additional information is available for downmixing.
Preferred downmix mode
Indicates if the producer would prefer a Lt/Rt or a Lo/Ro downmix. Can be over-ridden by
the decoder.
Lt/Rt center mix level
Indicates the required level reduction of the center channel when mixed with the L& R
channels for a Lt/Rt downmix. Similar to 'Center mix level'.
Lt/Rt surround mix level
Indicates the required level reduction of the surround channels when mixed for a Lt/Rt
downmix. Similar to Surround mix level'.
Lo/Ro center mix level
Indicates the required level reduction of the center channel when mixed with the L& R
channels for a Lo/Ro downmix. When present this replaces the value set for the 'Center
mix level'
Lo/Ro surround mix level
Indicates the required level reduction of the center channel when mixed for Lo/Ro
downmix. When present this replaces the value set for the 'Surround mix level'.
Dolby Surround EX mode
Flags if the stream has been encoded in 'Surround Ex'. Only used if surround channels are
present.
A/D converter type
Indicates type of A/D conversion used.
Digital de-emphasis
To meet the Dolby Digital encoding algorithm specification the audio must not have pre-
emphasis applied. If the input signal does have pre-emphasis applied, a de-emphasis
filter must be applied prior to encoding.
DC high pass filter enable
Removing the DC component can lead to more efficient encoding, but there is a risk that
signals that do not reach 100% PCM may exceed this after filtering and therefore must be
clipped.
Bandwidth low-pass filter
enable
Remove high frequency signals before encoding. The filter removes frequencies that
would not normally be encoded.
Low-frequency effects low pass
filter enable
Apply a 120 Hz low pass filter prior to an encode. Should only be switched off if it is
known that there are no frequencies above 120 Hz.
Surround attenuation enable
Attenuate surround channels by 3 dB before encoding. Theatrical and consumer mixing
rooms use different levels for the surround channels, and this can be used to compensate.
Surround phase shift enable
Apply a phase shift of 90 degrees to the surround channels. This simplifies the decode
process for producing a 'Lt/Rt' downmix.
Parameter
Description
Decoder Main Input
Specifies the main decoder input source, ie, the source of compressed (Dolby E) audio frames.
Set to ‘Off’ to disable the audio decoder.
Decoder Switchout
Input
This source is used when Dolby E ‘switchout’ is active. This input must always carry uncompressed audio
(linear PCM).
© Ericsson AB 2011. All rights reserved
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