This program is a Winamp input plugin to play .ac3
files. Based on the same decoder library used in AC3Filter.
Distributed absolutely for free (FREEWARE). Sorry if my English
is bad, but I think it is better to have something than nothing.
Just unzip and copy in_vac3.dll to Winamp plugin directory. Import preset.reg file (optional).
Uninstall.
Just delete in_vac3.dll from Winamp plugin directory. Inmport unintsall.reg to clean the registry.
Settings.
* Bitstream information.
Top left it is bitstream information (BSI):
Ñhannels - channels configuration
in form front_channels/surround_channels + LFE (Low frequency
effects channel) presence flag. In this example it is 3 front,
2 surround and LFE channels, i.e. 5.1 configuration.
Sample rate [kHz]
Bitrate [bps]
Freq (coupl/high) - [kHz], coupling
frequency and high freuency. In ac3 some channels (in most cases
all channels) are grouped in one coupling channel beginning
from some frequency - coupling frequency and stored in the bitstream
in that form. So channels are really independent only in some frequency
band - up to coupling frequency. High frequency is a maximum frequency
coded, so it defines total frequency bandwidth.
Frames/errors - total number of
decoded frames and number of errors when decoding.
* Gain levels.
Buttom middle it is gain level controls.
Master - desired gain level.
Gain - shows current gain level.
LFE - LFE channel gain level
Voice - center channel gain level (dialogue channel)
Surround - surround channel(s) gain level..
BSI Lock checkboxes - lock channel gain level at values given
by standart. You cannot change Voice, LFE and surround gains when it is
enables.
Master and Gain controls are responsible for global gain level.
Master sets desired gain level. If current sound level is too high
and overflow occurs then real gain level will decrease. Current gain
level shown at Gain control.
* Dynamic range compression.
By its nature ac3 is a logarithmic format. Samples
are stored in form of exponents and mantissas. In terms of bits
one sample can be up to 40bits long (only theoretically) or up to
24bits (normal). It provide huge dynamic range (but, as said by great
Einstein all good things in this word are relative :-). This means that
quiet sound with low level when played on 16-bit sound card will be not
audible at all or will have very low absolute level (=> high distortions).
To solve this problem it is dynamic range comression. Main idea is to raise
level when sound is quiet (and vice versa when loud) before converting
to 16-bit form. There are special markers in ac3 stream for current level
change. This markers are set by producer at a mastering stage, so it guarantees
high quality. DRC level indicates this level. With 'Use DRC' chekbox you
can enabe/disable using DRC. (of course this is only rough problem
description).
DRC Power control adjusts how much
DRC level changes sound level. When DRC Power is increased all quiet
sounds will be more stressed and loud sound will be more shaded. When
decrease DRC Power dynamic range compression will have less influence
at output. Zero DRC Power level means that dynamic range compression applied
at normal.
* CPU load.
Indicates CPU load by sound decoding and processing.
All sound processing (if exists) before reproduction included
here. (it is not working by now)
* Input/output levels.
Right part - levels indication. Note
that levels here are in logarithmic scale. Input levels shows real
channels configuration. Often happens that when BSI shows 5.1 in
real LFE channel is absent.
* Presets
Combo box at bottom right allows to load predefined sets of settings
(presets):
standart - maximum standart compatibility
one-pass normalize - as named, for maximum loudness.
LFE boost - LFE boosted at +10dB.
* Options
Normalize marix - matrix normalization. When this option is
enabled matrix is normalized so it is no overflow at output (sum of channels
at output < 1). But when gain level LFE, Voice or Surround changes other
chanel gain level will be also changed (for example if we increase level
of LFE other channels level will be decreased). Disable of this option allows
to avoid this effect. But overflow is possible in this case. So you'd better
to decrease Master gain when this option is disabled.
One-pass norm - one-pass sound normalization. When this option
is enabled autoatic gain control works this way. When overflow occur it
decrease current gain proportionate to overflow level (so it si no overflow
at output) and gain level remains at this state until next overflow. Master
is starting gain level. When this option is disabled current gain is always
changing towards Master gain. So after overflow current gain will increase
bit by bit until it reaches Master or other overflow occur. This mode is
used when no overflow is expected. But if it is happen nevertheless gain will
be restored after some time.
Expand stereo - works only when input mode is stereo. Allows
to amplify out-of phase signal components. It works as surround sound amplification
but not the sounds in center (dialogues are not amplified). Surround control
works as amplification level. If rear speakers are present at output this
out-of phase components routed there.
Voice control - works only when input mode is stereo. Allows
to amplify in-of phase signal components. It works as center amplification
(dialogues). Voice control works as apmplifiction level. If center speaker
is present at output central component routed there.
Distribution.
This program distributed under GNU General
Public Licence v2, placed in GNU_eng.txt at english language and GNU_rus.txt
at russian language. Russain language version is only for information purpose
only and english version have priority with all variant reading.
This application may solely be used for demonstration and educational
purposes. Any other use may be prohibited by law in some coutries. The
author has no liability regarding this application whatsoever. This application
may be distributed freely unless prohibited by law.
This product distributed in hope it may be useful, but without
any warranty; without even the implied warranty of merchantability
or fitness for a particular purpose and compliance with any standarts.
I do not guarantee 24-hour (and any) support, bug correction,
repair of lost data, I am not responsible for broken hardware and
lost working time. I am not responsible for legality of reproducted
with this program multimedia production.
Contact author.
With all questions about this program please, email to this address. Please,
respond about all errors in porgram.
Changelog.
0.2a - 20.11.2002
* Everything was rewritten :)
+ Configuration dialog added.
+ Settings are saved to registry.
