foo_dsp_fsurround, a new surround processor for foobar2000 0.9.x Options

[pro_optimizer]

FreeSurround
is meant to be the foobar2000 equivalent of your hi-fi receiver's Dolby ProLogic II button (except that it uses a different algorithm).
Its purpose is to decode surround information from your stereo music (including mp3, of course), and to produce 5.1 output from it. It works with any stereo music containing surround info in a coding scheme compatible with any the following decoders:
- Dolby Surround
- Dolby ProLogic
- Dolby ProLogic II
- SRS CircleSurround
- SRS CircleSurround II
- DTS Neo:6
- Lexicon Logic7
- Stereo Quadrophonic (SQ) *
- Quadrophonic Stereo (QS) **

It will also faithfully play back your 'plain old' stereo music, with the exception that echoes are usually played over the surround speakers, and some sound sources, usually strongly distorted guitars, choirs etc., tend to surround the listener instead of being played over the front speakers alone.

Download
The plugin is attached at the bottom of this post.

Operation notes
In contrast to the other foobar2000 surround processors (Channel Mixer, Matrix Mixer and ATSurround Processor, as of Aug. 2008), FreeSurround provides independently steered surround channels, and very low crosstalk between channels. If your want to check the state of your surround decoders, you find a test mp3 file at the bottom of the post. It will play a voice on your left front, left rear, right rear, right front and center speaker (one speaker at a time) -- if your decoder is good; otherwise there will be some mishmash on the other channels. Also, FS, being a surround decoder, should not be confused with DSP effects which merely give you an enriched stereo experience, such as Creative CMSS 3D and foobar's Convert Stereo to 4 Channels, or common DSPs like Stadium, Hall etc. Nevertheless there are some options to upmix plain stereo content meaningfully.

Configuration notes
Here is a screen shot of the default settings in the config dialog (these happen to be also the settings that I use at home).


The default settings are good for many surround setups, but there are some tweakable options (see screen shot).

• The sound field right after the decoding stage can be pictured as a 2-dimensional square with the listener at its center; this sound field can be further transformed spatially in several ways. The default setting is to leave the decoded field as it is, i.e., if a stereo track was downmixed from a discrete 5.1 track (e.g., from AC3 format) and is upmixed again with FreeSurround, it comes closest to the original source material when using the default settings. However, music that was not originally meant for surround playback can be spiced up quite a bit using these controls. The first option (Panorama) is to wrap the sound field around the listener in a circular manner. The slider allows to change the angle that the front soundstage takes up (i.e., the line between the front left and the front right corner of the sound field). Originally it is 90 degrees, but if it is set to, say, 270 degrees the front stage will be wrapped from behind the left ear along the front to behind the right ear of the listener. While the front stage is expanded, the side and rear sound field must correspondingly be compressed into the remaining space behind the listener. The second option (Dimension) allows to shift the sound field forward or backward without changing the shape. The third option (Depth) essentially scales the sound field to the back, i.e. the original square is resized along one axis (while the front stage stays where it is). These transforms are applied in the order in which they are listed here (the order matters). The last slider (Focus) is a bit experimental -- it allows to change the angular spread of the individual sound sources, either by making them more focal or less (i.e., more ambient). This is only really noticable with lots of speakers, but I would not overdo it.
• The second group of controls is how the sound field is mapped onto the speakers. The first setting here is the channel setup; this allows you to select how many speakers you have and where they are placed (front left and right, center, rear left and right, side speakers, etc.). From the point of view of the decoder there at 16 possible positions along the edges of the square sound field (see this picture for an example), namely the 4 corners, the 4 midpoints (front center, back center, left side, and right side), and two positions on each edge half-way between the corners and the midpoint (e.g., front left center, front right center). Most people have only a subset of all these channels (e.g., 7.1) in some common locations, but you can have some fairly arbitrary setups (***). But note that the placement of the speakers in the room is actually not in a rectangle but instead follows the corresponding home theater rules. If you have a subwoofer you might want to do the bass management right here, but it is usually a better idea to let the sound card or amplifier do it if they offer the option (e.g. for active sub-satellite systems). The last option in this box is the stereo separation; this allows to effectively stretch the sound field horizontally in the front and/or back areas.

Change log
0.9.0
- fixed a steering bug in the 0.8.1 beta (sound field was shifted by a few degrees to the left due to an oversight; also steering was less accurate than it should have been)
- removed a library dependency (boost serialization) that could cause conflicts with other plugins using the same library but different version (to be confirmed as fixed)

0.8.1 (beta)
- basically a rewrite & cleanup; see this post for more details on the original beta announcement.
- supports more speaker arrangements (up to 16.1)
- supports more controls for sound field transformations (shift, stretch, wrap, ...)
- probably a bit faster, too

0.3.5
- now much faster when switching tracks

0.3.4
- new front and rear stereo separation controls
- 4 phase shifting modes are supported now
- new linear steering mode (better than the old one)
- fixed the dimension slider (negative values were mapped to 0)
- the gain is back at 100% due to request (you can still put the equalizer before FS to control the gain)

0.3.3
- added the option to invert the rear phase (like pl2 movie mode)
- added the option to specify the (surround) mixing coefficients which are assumed for decoding

pre-0.3.3
- changed "center width" into "center image", which controls how present the center speaker is (0.3-0.7 are good values for music).
- expanded the range of "dimension" to [-0.5 .. 1.0] where 0 is a normal surround soundfield, -0.5 moves the sound towards the front, 1.0 moves it backwards.
- changed the gain to ~85% to avoid clipping in practically all cases.
- fixed center/surround level (both were too loud it appears).


* SQ is decoded with mono surrounds (i.e. like ProLogic I), due to a defective coding specification.
** QS requires the front stereo separation to be set to 1.5, or else the sound field will be too narrow.
*** There is one little catch with the more exotic channels: foobar2000 (or Windows) do not expose some of the rarely used positions but instead allow to connect "top" speakers (meant for the ceiling). Therefore there is a bit of remapping going on for these positions: If you have 'side front left'/'side front right' speakers, connect them to the 'top front left'/'top front right' channels, if you have 'side back left/right' connect them to 'top back left/right', and if you have 'back center left/right' speakers you need to connect them to the 'top front center' and 'top back center' channels, respectively.

This post has been edited by pro_optimizer: Sep 25 2012, 04:05

Attached File(s)

 foo_dsp_fsurround_0.9.0.zip ( 333.2K ) Number of downloads: 4205
 channeltest.mp3 ( 69.99K ) Number of downloads: 1286

 

[pro_optimizer]

Hi Pro-opt

This post is only to ask your opinion about a couple of things I have been trying these days regarding Dolby surround.

First one is AC3, I'm using Eright Software Super Encoder/decoder to transform my music files into AC3, getting that way Dolby Digital directly from spdif soundcard out. Super uses a ffmpeg library to process the music, there are some mentions of this Dolby encoding system in hydrogenaudio forums, they say it's not such a great thing, but to my ears this Dolby digital gives better sound than Dolby prologic. This Dolby Digital Spdif music bypasses completely all the controls in my X-Fi extreme music, I can change the volume only with the receiver.

Second one is that redocnecxK program that supposedly encodes al your sounds into AC3 and sends them directly to the receiver through spdif. I says supposedly because it doesn't work with X-Fi sound cards.

So my questions at the end are about the difference between hearing AC3 encoded music and music filtered through your Dolby plugin.

Thanks anticipated,
Rozzo

Hi Rozzo,

since I have never used ffmpeg/redocnecxK I don't really know how good it is and what it does.
But if it upmixes music to ac3 then it must obviously generate the surround channels from somewhere.
And there are basically 4 options:
1: from the front channels by mirroring, delay, echo (e.g. concert hall effect)
you can get this from you sound card, too (by enabling CMSS 3D or some EAX effects)

2: by passive matrix decoding (this is what dolby surround did)
then you can get a similar or better effect with foo_channelmixer.

3: by active decoding like pl1 does
if this is the case it should not sound better than FS

4: by active decoding like pl2 does
in this case it should sound similar to FS (depending on how good/bad the implementation is)

The fact that it is transferred via AC3 should not make a noticeable difference (except if you have really really bad cables/connectors).

Maybe you can post a few links to the programs?

ATSuround Encode2 works, in volume, like coeficients 1/0.7071/0.8165/0.5774, but the rear channels seems phase shifted then can't be recovered exactly by Free Surround (good channel separation) or PowerDVD (and worse channel separation).

With ATSurround Encode2 I don't know how disable LFE (don't be present in dpl II), and seems be amplified because there are big overflows.

If ATSuround Encode2 put one option to disable the rear phase shift and other to disable the LFE in downmix become usable for me. I have a old audio equipment attached to the PC with only dpl decoder then to listen ac3 5.1 need a downmix to dpl and need ffdshow/ac3filter, can't with Foobar. I don't see any plugin with matrix style, like ffdshow/ac3filter, to make the downmix.

Thanks.

Yeah, I got the same results (just a few hours ago, should have checked the board before I started
And your're right with the phase shifting.
Unfortunately it's hilbert filter cuts a lot of the lower and higher frequencies (the passband is approx. 110 Hz to 3.5 KHz).

Do you really need only an AC3 downmixer plugin (without phase shift)?
In this case I could write one... should be a matter of minutes.
Actually I need a replacement (with optional [and perfect] shift) for Encode2, too.