Surround sound or better support for it(proposal)

[X86]

Hi

The sound with the wma codec is great,it even has like surround sound,is it there a way to make better surround? or in the effect that I'm wrong,make surround sound support?.The wma codec plays the music great,its like a sitting in the beach watching the sunset,its maginificent,great job.

If it could be made,it would be great to apply that to the other codecs.

Thanks for reading the topic.
Regards.
Gilberto Ramirez Hernandez

[Llorean]

The players have stereo output. That's two channels. Surround sound requires more output channels, which requires different hardware.

The only players that could do surround sound are those with digital output (h100 series, some Archoses), and in that case it's more or less just taking a surround file and passing the bitstream on to the receiver and letting it deal with the decoding.

[glubash]

You might be able to find a Dolby Pro Logic decoder (most receivers should have it built in) and run the output through that to get 4 channels (L, R, Center, and Rear).  But, I'm not sure if wma or mp3 will preserve the Dolby phase shift to get the other channels or if it would be lost in the translation.  If you used a lossless codec??? 

For sure, you would have to have an external decoder though since you only have 2-channel output.

Ref. page:  http://en.wikipedia.org/wiki/Dolby_Pro_Logic

Glubash

[saratoga]

The sound with the wma codec is great,it even has like surround sound,is it there a way to make better surround?

The WMA codec doesn't do surround because WMA standard is 1 or 2 channel only. 

[TexasRockbox]

If one had an old (70's) quad SQ encoder/decoder one could have multichannel from that from two channels.  Some CDs were actually released of using some of the old SQ mixes.  To bad one couldn't record/playback 30khz (the CD-4 carrier frequency), then CD-4 could be used and it would be discrete four channel.

[MajiKool Dragonâ„¢]

what if you output the bit stream through the regular headphone jack and built/made/used/found some sort of small/compact(well i guess it doesn't really matter how big or small it is since you would have to use speakers... headphones can only output two channels.) external decoder that can decode this signal and output four audio channels.

[saratoga]

what if you output the bit stream through the regular headphone jack

Headphone jacks are analog, not digital.

[Multiplex]

Pink Floyd were famous for making stuff appear in 3D space in stereo recordings (I know not how) and there is lots of discussion about the phase and amplitude effects caused by the shape of the ear which may expalin how you work out what is in front and what is behind you.

It is entriely palusible that a lossless or a very well compressed recording may still carry the subtle information to give the spatial hints to the brain.

BUT if you read up on how the various lossy compression algorithms work you'll appreciate that it is unlikely, maybe it is the effects of the compression (artifacts) that are producing the spatial effects you are experiencing...

[MajiKool Dragonâ„¢]

what if you output the bit stream through the regular headphone jack

Headphone jacks are analog, not digital.

but it is still possible to out put a "digital" signal through this analog output. the signal itself would still be output as analog but it would be a digital-ish signal thats being output. you'd just need to make/modify a decoder to decode this "digital" signal.

[soap]

but it is still possible to out put a "digital" signal through this analog output. the signal itself would still be output as analog but it would be a digital-ish signal thats being output. you'd just need to make/modify a decoder to decode this "digital" signal.

A CD is 1,411,200 bps.
A MP3 might be 128,000 bps.
AC3 audio might be 448,000 bps.

The peak audio frequency your analog output can create is probably 22 or 24 Khz.
24,000 cycles per second.

Unless I am mistaken somewhere, you are going to need to figure out a way to dramatically compress your "surround sound" bitrate.

[MajiKool Dragonâ„¢]

but it is still possible to out put a "digital" signal through this analog output. the signal itself would still be output as analog but it would be a digital-ish signal thats being output. you'd just need to make/modify a decoder to decode this "digital" signal.

A CD is 1,411,200 bps.
A MP3 might be 128,000 bps.
AC3 audio might be 448,000 bps.

The peak audio frequency your analog output can create is probably 22 or 24 Khz.
24,000 cycles per second.

Unless I am mistaken somewhere, you are going to need to figure out a way to dramatically compress your "surround sound" bitrate.

hmmm... you've got a point.

[dreamlayers]

It's possible to output surround sound via headphones using just two channels.   For example there's binaural recording, which records sound at the ears.  Another example is some software which can downmix sound for headphones in a way which preserves 3D sense of direction.  CyberLink PowerDVD and ffdshow can do this.  It's not perfect but it's better than stereo.  Ffdshow is open source and may have code which can be used in Rockbox.

Note that Rockbox can already play binaural recordings or files which have already been downmixed using such algorithms.  They're just normal stereo files.  Many binaural samples are available online.

[markun]

It's possible to output surround sound via headphones using just two channels.   For example there's binaural recording, which records sound at the ears.  Another example is some software which can downmix sound for headphones in a way which preserves 3D sense of direction.  CyberLink PowerDVD and ffdshow can do this.  It's not perfect but it's better than stereo.  Ffdshow is open source and may have code which can be used in Rockbox.

I once read a review of QSound where the reviewer first was very sceptical, but later blown away by the results. I haven't tried it for myself. I would also like to see such an algorithm for rockbox, especially for playing back Ambisonics recordings.

The crossfeed effect we have in rockbox moves the sound from inside my head to the front of it. I've heard that the effect doesn't work for everyone (since our ears and heads are different) so I wonder how well such a 3D simulation algorithm could work. Well.. as long as it works for my ears