At this page you can control SPDIF output options. For the in-depth description about what SPDIF is, now it works and how to configure AC3Filter, read AC3Filter & SPDIF article.
 Output format
 Decoder info
Shows the decoder information, that may be helpful to track problems with SPDIF setup.
 SPDIF passthrough
Here you can select audio formats that you want to transmit to your receiver without any change (passthrough). Audio tracks with the selected formats will be decoded by the receiver and AC3Filter acts as an agent between the media player and the receiver.
It is just because of the essence of this mode: no processing can be done without decoding of the sound, and the decoding is done at the receiver. So only the receiver can affect the sound.
 SPDIF/DTS mode
DTS can be transmitted over SPDIF in 2 modes:
- Packed into SPDIF frames
- In this case each DTS frame is wrapped into an SPDIF frame. Because of an additional frame header, this method introduces an overhead. This overhead is quite small, but some DTS tracks have bitrate that match SPDIF bitrate exactly, so even the small overhead prevents the track from being passed through.
- Padded with zeros to match SPDIF bitrate.
- In this mode each DTS frame is transmitted without any additional headers. This allows to transmit DTS tracks ripped from multichannel AudioCDs. But it is some risk of getting a LOUD noise instead of the normal sound.
Note that some DTS tracks with high bitrate cannot be transmitted over SPDIF at all.
Auto option tries to enable packed mode when possible and downgrade to padded only when necessary.
 SPDIF/DTS conversion
See What is 14bit DTS fot more info about 14bit DTS.
- Do not convert
- Do not convert DTS stream type.
- Convert to DTS14
- Convert 16bit DTS tracks to 14bit DTS format.
- Convert to DTS16
- Convert 14bit DTS tracks to 16bit DTS format.
 SPDIF options
- Detect SPDIF stream in PCM data
- Multichannel AudioCD rips are often WAV files. The format of this file is indicated as stereo 16bit PCM. So when you play this file you can hear just noise.
- This option solves this problem. When it is enabled, AC3Filter scans stereo PCM tracks (that only can carry a digital transmission) for SPDIF synchronization. When sync is found, it extracts and decodes the contained AC3/DTS content.
- Use AC3 encoder
- This option enables AC3 encoder, so you can route multichannel audio to the receiver using digital connection.
- Do not encode stereo PCM
- This allows not to encode stereo tracks, because it does not need to be encoded. Stereo can always pass the digital connection precicely without any encoding loss of quality.
- AC3 encoder bitrate
- Bitrate for AC3 encoder. 640kbps (maximum allowed) is always recommended.
- Output SPDIF as PCM
- When driver does not support SPDIF, but can pass audio procisely, you can force SPDIF output using this option (see SPDIF-as-PCM trick).
- Restrict SPDIF sample rate
- Most sound cards suport only one output sample rate. Using other sample rates for SPDIF output may produce problems. When this option is enabled, AC3Filter checks that output sample rate is explicitly allowed.