AC3Filter ver 0.6b

Main features:

• Full AC3 standart compliance.
• S/P DIF passthrough support.
  
• Decode MPEG2 PES streams.
• Multichannel output support.
• LFE support.
• Dynamic Range Compression (DRC) support.
• Overflow control and automatic gain control.
  
• Gain levels control.
• Bitstream information (channel format, bitrate, sample rate, coupling freq and maximun freq).
• Input/output levels.
• Matrix mixer with direct control of mixing matrix.
• Stereo to multichannel mixing.
• DolbySurround/ProLogic/ProLogicII downmixing.
• Equalizer.

Contents

• Download.
  
• Install.
• Uninstall.
• Usage
• Main settings
• Mixer settings
• Equalizer and delay
• Configuration advices
• Windows 98
• General advices
• Maximum standart compatibility
• One-pass normalize
• Registry
• Presets
• Mixing matrices
• Misc
  
• Distribution.
  
• Contact author
  
• Changelog.
• Useful links.
  

Download.

Install.

Uninstall.

Usage.

• Command file config.bat
  
• Command line command "rundll32 ac3filter.ax,config"
• When playing if player lets access to filter properties (WMP 6.4, BSP, Sasami, etc. WMP9 does not!). For example in WMP 6.4 filter list can be accessed File->Properties->Advanced:

Main settings

• Сhannels - 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.

* Speaker configuration switch.

• All audio streams are ac3. mmswitch may be used in any speaker configuration. Speaker switch 'on place' will not work. So you'll need to set it before playing.
  
• First stream is ac3, and second is mp3 (just for example, may be any non-multichannel format (stereo or mono)). If ac3 is needed then everything is ok. You'll need only to set desired speaker configuration in Control Panel before playing because of online switch will not be available. If you'll try to switch to mp3 you'll get bad sound because audio with only stereo channels will be played as audio having quadro (for example) channels. So if you want to play mp3 track you'll need to set stereo speakers in Control Panel.
• First stream is mp3 and second is ac3. In this case it is only stereo playing possinble. Do not forget to set it before playing!
• No ac3 streams - no problem :).

• 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.
• Normalize - one-pass sound normalize. (look at Mixer settings)

* Dynamic range compression.

* CPU load.

* Input/output levels.

* Presets

• standart - maximum standart compatibility
• one-pass normalize - as named, for maximum loudness.
• LFE boost - LFE boosted at +10dB.
  

Mixer settings

• Auto matrix - automatic calculation of mixer matrix. When this option is enabled direct edit of mixing matrix is disabled. Gain levels LFE, Voice and Surround are parameters for matrix calculation. When this option is disabled next controls loose influence: Gain levels LFE, Voice and Surround, Normalize matrix, Expand stereo, Voice control. Following controls are remain to work: Master, Gain, DRC level, DRC power, One-pass norm. Direct matrix edit is enabled.
• 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.

Equalizer and delays.

• Compensate different distance from speakers to listener. In ideal all speakers sould be placed at equal distance from listener so sound simultaneously expressed from all speakers come to listener at the same time. In this case one unit means 1U = 330 [m/s] / 48000 [Hz] ~=7 [mm]. Common formula for delays when all distances are known: delay(ch) = d(ch) [m] * sample_rate [Hz] / 330 [m/s], where delay(ch) is audio delay for channel ch, d(ch) - diatsnce to speaker ch, sample_rate - in most cases is 48000Гц, 330 m/s - acoustic speed. Simplified formula for most cases: delay(ch) = d(ch) [мм] * 0.145.
• Delay for synthesized rear channels (when Expand stereo option is on).

Configuration advices

Windows 98

General advices

• Always check speaker setting.
  
• Use stereo output under Windows 9x if other modes do not work.
  
• When downmix from 2/2 or 3/2 to stereo it is safe to increase a little Master gain level, since level af rear channels is usually lower then front channels level.
• Too loud transltor voice level can be lowered with Voice control. If it is stereo sound track then Voice control needs to be enabled.
• Dolby recommends increase LFE mixing level up to 10dB. But in this case other channel level is decreased (when Normalize matrix option is enabled) or overflow possible (when Normalize matrix option is disabled).

Maximum standart compatibility

• Master = 0dB
• DRC Power = 0dB
• BSI lock = all on.
• Auto matrix = on.
• Normalize matrix = on.
• One-pass norm = off.
• Expand stereo = off.
• Voice control = off.
  

One-pass normalization.

• Master = +10..+20dB
• One-pass norm = on.

Registry.

Presets

• mode (int) - speaker configuration, set on preset load. This value may be absent. In this case speaker configuration will not be changed on preset load. Can be one of:
  

  Value	Meaning
  0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15	2/0 (stereo) 1/0 (mono) 2/0 (stereo) 3/0 2/1 3/1 2/2 (quadro) 3/2 2/0+LFE 1/0+LFE 2/0+LFE 3/0+LFE 2/1+LFE 3/1+LFE 2/2+LFE 3/2+LFE (5.1)

• spdif (int) - turn on SPDIF passthrough.
• dolby (int) - turn on Dolby downmixes:

  Value	Meaning
  0 1 2	- Dolby Surround/ProLogic Dolby ProLogicII

• format (int) - output sample format:

  Value	Meaning
  0 1 2	PCM 16bit PCM 24bit PCM float

• matrix (text) - name of mixing matrix to set on preset load. Make no sence when auto_matrix option is set. This value may be absent. In this casae mixing matrix will not be changed on preset load.
• master (double) - main gain level
• clev (double) - central channel gain level
• slev (double) - surround level gain level
• lfelev (double) - LFE channel gain level
• clev_lock (bool) - central gain level lock
• slev_lock (bool) - surround gain level lock
• lfelev_lock (bool) - LFE channel gain level lock
• dynrng (bool) - use dynamic range compression
• dynrng_power (double) - dynamic range compression power
• auto_matrix (bool) - use automatic matrix calculation
• normalize_matrix (bool) - normalize mixing matrix
• expand_stereo (bool) - extract surround from stero input
  
• voice_control (bool) - extract center from stereo signal
• eq_on (bool) - equalizer on
• delay_on (bool) - delay adjustments on.
  

Mixing matrices.

Misc.

Distribution.

Contact author.

• Problem description
  
• Windows version
  
• Sound card
• Player used and its version
  
• Registry key HKEY_CURRENT_USER\Software\AC3Filter
• Speaker configuration used (stereo, quadro, 5.1...).
• If filter's property page can be opened then data from 'bitstream information'.
• If you know what Graphedit is, then also screenshot (or just description) of graph caused problem.
• If problem connected with incorrect sound then send a part of ac3 stream caused problem.
  

Changelog.

Useful links