Most receivers are able to decode AC3 (= Dolby Digital) and DTS audio. If you have connected your receiver to your PC with a digital cable, then you can send AC3 and DTS audio directly to your receiver using a S/PDIF or HDMI connection. Modern receivers even support HD audio formats such as E-AC3 (= Dolby Digital Plus), Dolby TrueHD, and DTS-HD MA (Master Audio). Sending the compressed audio directly to a receiver is called bitsteaming or passthrough. The location of the audio bitstreaming options depends on which decoder that you are using, either LAV Audio decoder, ffdshow or AC3Filter. The codec pack uses LAV Audio decoder by default. [1] General information You should enable passthrough only for those formats that are supported by your receiver. Check its manual to see what it supports. S/PDIF only supports passthrough of AC3 and DTS. When sending uncompressed audio (PCM) it supports only stereo (2.0). HDMI has more bandwidth and supports all formats mentioned above. In case of uncompressed audio it supports up to 7.1 channels. The filters in the codec pack also have the ability to convert audio to AC3 in realtime. This allows you to bitstream audio that otherwise is in an unsupported format for bitstreaming, such as AAC. This can be useful in case of S/PDIF. For HDMI it is usually not needed. The filters required for this conversion functionality are only included in the Mega version of the K-Lite Codec Pack. See section 3 below for more details on the configuration settings. [2] Basic configuration The codec pack installer offers options to configure passthough. See below on how to configure when the pack is already installed. [2a] Codec Tweak Tool You can easily configure audio bitstreaming this way: Codec Tweak Tool > Audio Output This automatically applies the chosen settings to the audio decoders that were installed by the codec pack. See below how to manually configure the decoders. [2b] LAV Audio decoder (default) The settings in LAV audio decoder should be obvious. Simply tick the checkboxes for those formats that you want to passthrough. Remember, that when using S/PDIF you should only enable AC3 and DTS. [2c] ffdshow audio decoder In ffdshow audio decoder configuration, go to the "Output" page. There you can find checkboxes to enable passthrough for AC3, DTS and other formats. If you have problems getting pass-through to work properly, then try disabling the "Connect as PCM first" option in ffdshow. [2d] AC3Filter To activate S/PDIF output, enable the checkbox called "Use SPDIF" that is located on the "Main" tab. All S/PDIF options in AC3Filter are located on the "SPDIF" tab. Be aware that AC3Filter does not support passthrough of E-AC3, TrueHD, and DTS-HD. If you want AC3Filter to process audio that was decoded by a different DirectShow filter, then you need to enable PCM on the "System" tab. [3] Convert unsupported formats to AC3 When using S/PDIF connection you have two choices for unsupported audio formats: - Decode it on the computer, mix it to stereo, and then passthrough as stereo PCM.
- Convert to AC3 and then passthough.
Below you can see several ways to convert to AC3. Pick one of those methods if you want to [3a] Convert to AC3 with MPC-HC with LAV audio decoder and ffdshow audio processor This is recommended if you use MPC-HC as preferred player. - Enable use of ffdshow audio processor:
MPC-HC options > External Filters > Add Filter > Select "ffdshow audio processor" and set it as preferred (there also is an option in the K-Lite Codec Pack installer to do this automatically) - Once added, double-click on its name to access the settings of ffdshow audio processor
- In the settings make these changes:
* Enable Resample and set it to 48000 Hz. * Enable Mixer and set it to 3/0/2 speakers and enable LFE checkbox. Optionally you can enable "Expand stereo to surround" if you wish to upmix stereo inputs. * On the "Output" page, enable passthrough for AC3 and "AC3 (S/PDIF encode mode)" output format. - In the settings of LAV Audio Decoder disable the Mixer.
[3b] Convert to AC3 with ffdshow audio decoder This only works if you are using ffdshow for decoding the formats that you want to convert, or if you use ffdshow for procesing uncompressed audio (PCM). Make the following changes in the settings of ffdshow audio decoder: * Enable Resample and set it to 48000 Hz. * Enable Mixer and set it to 3/0/2 speakers and enable LFE checkbox. Optionally you can enable "Expand stereo to surround" if you wish to upmix stereo inputs. * On the "Output" page, enable passthrough for AC3 and "AC3 (S/PDIF encode mode)" output format. [3c] Convert to AC3 with AC3Filter audio decoder This only works if you are using AC3Filter for decoding the formats that you want to convert, or if you use AC3Filter for procesing uncompressed audio (PCM). All you need to do, besides enabling SPDIF passthrough, is tick the "Use AC3 encoder" checkbox. [4] Troubleshooting tips If passthough still does not work in MPC-HC after doing correct configuration, then check if the correct audio device is set as default in the Windows Control Panel. You can also explicitly select the desired output device in the settings of MPC-HC: MPC-HC options > Playback > Output > Audio Renderer (select the correct device and choose the one with DirectSound prefix) In some cases you may need to disable the following option in LAV Audio Decoder: "Fallback to PCM if bitstreaming is not supported" [5] Volume control If you passthough a compressed format to a receiver, then the receiver is responsible for the decoding and only the receiver can adjust the volume. The computer can't modify the audio or volume. |