How do I know if a 2.0 WAV is surround or stereo?

[zee944]

When you have a two channel signal, how can you decide if it's Stereo or true Surround?

I'd really like to learn a reliable way to know it. Simple listening the signal won't tell you. If you put it through a DPLII decoder, it won't tell you anything either, as it'll play something in the surround speakers no matter if it's stereo or surround.

How can you find out if there is really a surround channel encoded into your 2.0 audio? Anyone?

[raquete]

strange that your decoder don't give infos, my Sony decoder show when is Dolby surround(2.0, etc)
adjust your decoder to "auto" and test.

[zee944]

strange that your decoder don't give infos, my Sony decoder show when is Dolby surround(2.0, etc)
adjust your decoder to "auto" and test.

What decoder would tell about a 2.0 WAV file if it's surround or not? Besides, I wouldn't trust a DVD company's claim.

[raquete]

2.0 WAV file if surround?
i don't know, sorry.
DVD company's claim 2.0 wav surround?
i never heard about that too.
have the name of the dvd source?

[tebasuna51]

Only Ac3 2.0 format have a flag in the header to say if is Dolby Surround encoded, after decoded to wav the flag is loss.

[rik1138]

Only Ac3 2.0 format have a flag in the header to say if is Dolby Surround encoded, after decoded to wav the flag is loss.

But the wave file would still be surround encoded... But I'm not sure how you can tell for sure.

AC3 does have a surround flag, but that requires that it be set properly when encoding (the person operating the Dolby encoder has to tell it that it's surround). The default setting in the encoder is 'not indicated', so I wouldn't be surprised if there's a lot of 2.0 audio encoded that way.

Playing it and listening is probably the best way. If you are getting clear left and right surround information (that matches what's happening on screen), then it was probably surround encoded. Anything else would just be a guess.

I believe the only way to really know for sure is to ask the person that made the sound mix... (Usually not something that's easy to do though... :cool: )

[zee944]

Thanks for the answers.

I've always felt this 2.0 surround thing is just a gimmick. I haven't seen a single "surround" movie at home (listening through DPLII decoder) which had any independent activity in the rear speakers (compared to the front speakers). I've never heard a voice, explosion, any sound effect coming from the rear speakers only. I've also read Dolby Surround can't really separate the front and the rear information, and the surround channel will always be mixed with the front (center) channel. This also confirms my theory. Being "compatible with stereo" also makes me suspicious.

Every sound expert I asked (in real life or in forums) gave evasive answers to my questions. Some of them told me pretty theories about how it works (in theory), but they couldn't really tell what could make anyone confident about Dolby Surround's capabilities.

If surround information presence can't be verified what holds back studios/filmmakers/DVD companies to put "Surround" label on stereo signals? You won't notice the difference anyway. And maybe that's what happens.

[tebasuna51]

You can use these samples to see if your DPL II decoder is working: DplSamples.7z (http://www.sendspace.com/file/r9yoit)

The AC3 file have the flag like surround encoded and must force the DPL II decoder, with the MP3 you need activate the decoder manually.

[Chabb]

I'm not sure, but spectral analysis
of surround encoded material looks different
compared to normal stereo
(in high frequencies one channel has "lighter" band
and the other - "darker" one in the same range)
Maybe this helps?

[zee944]

I'm not sure, but spectral analysis
of surround encoded material looks different
compared to normal stereo
(in high frequencies one channel has "lighter" band
and the other - "darker" one in the same range)
Maybe this helps?

I'd like to revive this thread.

Chabb hasn't been active for years. Only now I've seen his comment. Is this possible what he suggests?

It would be really cool to be able to distinguish the surround sound from stereo.

[tebasuna51]

Is this possible what he suggests?

I don't think so.

The dpl downmix don't difference low or high frequencies.