How to solve the problem macbook pro camera does not work

BACKGROUND:
week with normal qq video chat, which is suddenly displayed weeks undetectable camera. Open the facetime and photo booth also displays "The camera is not connected"
had to call Apple customer service after all the investigation and solve this problem with the help of customer service.

Solution:
1. Turn off.
2. Connect the power cord. Ensure that the computer other than the power line is not connected to any peripherals.
3. Press and hold the control, option and shift the lower left corner, press and hold for 15 seconds. This process, the computer will not have any reaction.
4. Press the power button immediately while holding down the option, command, P and R. After (The screen will be black and white) rang four times until you hear the computer boot (black and white black flashing 4 times) sound, let go. The computer will boot into the normal process.

After these operations, the camera can be used normally.

Later I checked the relevant information, which referred to:
* Hold down the control, option and shift the lower left corner, press and hold for 15 seconds.
This operation to solve the problem is to reset the System Management Controller (SMC) , with the words of Apple's customer service manual, called hardware reset.
The fan, the power indicator, system performance, video, when some abnormality occurs, may be reset by the aforementioned methods to resolve.

* Press the power button immediately while holding down option, command, P and R.
This operation to solve the problem is to reset NVRAM or PRAM .
Mac will be some settings are stored in a special area of memory, and even shut down these settings will not be lost (unless the battery problem). On Intel-based Mac, the storage location of the memory known as NVRAM; and on PowerPC-based Mac, the storage location is called PRAM memory.

Information stored in NVRAM / PRAM includes:

speaker volume
screen resolution
selected boot disk
recent kernel crash information (if any)
If the only problem associated with the above functions, may need to reset NVRAM or PRAM.
NOTE: OS X does not store the network settings in NVRAM / PRAM in. If you're troubleshooting a network problem, reset will not have any help.



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