# How to detect MP3 Stereo eXtended / Surround ?
**URL:** https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407
**Category:** General Discussion
**Created:** [June 4, 2006, 5:26pm UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407 "2006-06-04T17:26:37Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@DetlevD](https://community.mp3tag.de/u/DetlevD)
#### Post date: [June 4, 2006, 5:26pm UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407/1 "2006-06-04T17:26:37Z")
Is there any Mp3tag systemvar that can display if a mp3 file has been coded as 'MP3 Mono', 'MP3 Stereo', 'MP3 eXtended', 'MP3 Surround' and so on?
DD.20060604.2125
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### Author:  [@Sebastian\_Mares](https://community.mp3tag.de/u/Sebastian_Mares)
#### Post date: [June 4, 2006, 8:15pm UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407/2 "2006-06-04T20:15:38Z")
Only **%\_mode%** which returns Stereo, Joint Stereo and Mono if I am not mistaken.
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### Author:  [@DetlevD](https://community.mp3tag.de/u/DetlevD)
#### Post date: [June 5, 2006, 5:51am UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407/3 "2006-06-05T05:51:53Z")
Is there a chance to have **%\_mode%** returning 'MP3 eXtended', 'MP3 Surround' too?
DD.20060605.0951
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### Author:  [@Sebastian\_Mares](https://community.mp3tag.de/u/Sebastian_Mares)
#### Post date: [June 5, 2006, 6:29am UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407/4 "2006-06-05T06:29:15Z")
Don't think so. I just downloaded a test file and the MP3 frames are marked as Joint Stereo. I guess the surround information is stored somewhere else like SBR data is stored in mp3PRO.
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### Author:  [@DetlevD](https://community.mp3tag.de/u/DetlevD)
#### Post date: [June 5, 2006, 9:47am UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407/5 "2006-06-05T09:47:18Z")
> [@Sebastian Mares](#):
>
> Don't think so. ...
... hmm, the Fraunhofer IIS MP3 Surround Decoder WinAmp Plugin displays the different coding modes.
Maybe there are sources on the internet that describe how to detect those special modes, number of channels and something else.
I would like to see those mode ability in Mp3tag as soon as possible.
DD.20060605.1345
> [@](#):
>
> Excerpt from Audio Engineering Society, Convention Paper 6049, Presented at the 116th Convention, 2004 May 8–11 Berlin, Germany :
> 4.1. Basic Scheme
> ... The resulting stereo signal is encoded by a conventional
> MP3 encoder in a fully standards compliant way. At the
> same time, a set of spatial parameters (ICLD, ICTD,
> ICC) are extracted from the multi-channel signal,
> possibly considering the stereo downmix signals. These
> spatial parameters are encoded and embedded as
> surround enhancement data into the ancillary data field
> of the MP3 bitstream within a suitable data container
> that unambiguously identifies the presence of such data
> for decoders with corresponding extended capabilities
> (i.e. MP3 Surround decoding). This mechanism of
> extending MPEG-1 Audio bitstream syntax has been
> used repeatedly in the past to 'hide' various types of
> enhancement data in a backward compatible way, e.g.
> for embedding multi-channel audio extension or
> bandwidth extension data.
I do not know if surround mode is directly coded in the MP3 header bitfields but the quote above sounds to me that there is an 'ancillary data field of the MP3 bitstream' that might be evaluated.
DD.20060605.1421
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### Author:  [@Sebastian\_Mares](https://community.mp3tag.de/u/Sebastian_Mares)
#### Post date: [June 5, 2006, 6:25pm UTC](https://community.mp3tag.de/t/how-to-detect-mp3-stereo-extended-surround/3407/6 "2006-06-05T18:25:44Z")
Yep, as I thought - the surround information is stored in more or less the same way as the SBR information is stored in mp3PRO. However, I doubt Florian has any plans to implement support for these MP3s because they are not really wide spread - people who need more audio channels usually encode to Ogg Vorbis or AAC/MP4.
Edit: Oh, by the way - you are right that the Winamp input plugin recognizes the files, but since it's a decoder, it _has_ to parse the ancillary data, while Mp3tag relies on the frame headers which are much easier to spot and decode.