rtMedia json api fail to upload large images

I am using rtmedia json api to upload posts. I am able to upload the media successfully if the image is small. But the image taken using iPhone 4+ is not uploading as it is showing 413 “Request Entity Too Large”.

When i am using website from desktop browser i am not getting this error, the error is only when i am using rtmedia json api.

I am using cordova application for developing the app which is using rtmedia json api to communicate with the server

Is there any thing like setting image height width or size so that i can increase it.

I have already change php.ini but no use.

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