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Topic: Detect MONO in STEREO media (Read 3133 times) previous topic - next topic
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Detect MONO in STEREO media

I have got audio materials in two channels (stereo) mode, but suspect it authored from one channel (mono)  . How can i confirm this taking into account lossy compression applyed?

Detect MONO in STEREO media

Reply #1 –
If the two channels are identical, I don't think that any lossy codec will change this.

-Eugene
The  greatest  programming  project of all took six days;  on the seventh  day  the  programmer  rested.  We've been trying to debug the !@#$%&* thing ever since. Moral: design before you implement.

Detect MONO in STEREO media

Reply #2 –
Look at it in a WAV editor such as Nero's. If the two channels are exactly the same, then the file was created from a mono source. If you are really anal and want to be 100% sure, use a program such as Goldwave and select "remove vocals." This will invert one channel of the file you have and mix it with the other. By doing this, the two channels will "cancel each other out" per say. If the original file was mono, you should be left with one big silent audio file, or something very close to silent. Have fun!

Detect MONO in STEREO media

Reply #3 –
Cool Edit has a phase meter that shows the difference between the channels. If the channels are completely in phase, the line will be vertical. If completely out of phase (180 degrees) the line will be horizontal. The wider the pattern on the plot the more differences between the channels.

Wavetools has a vecterscope which will show you the same thing. 

-Iain
 

Detect MONO in STEREO media

Reply #4 –
Quote
program such as Goldwave and select "remove vocals."

Alternately, CoolEdit (other programs probably do too) allows you to convert Left-Right to Mid-Side (Transform | Amplitude | Channel Mixer). If you do that then one channel will become the common part between both channels and the other channel will become the difference between the two channels. If you have one silent channel then the two original channels are identical.

As a quick check you can just play the file in CoolEdit and open the Frequency Analysis graph and if you see only one line then you've got mono - stereo will give you distinctly different lines for left and right.