This article is only meant for advanced users - ones that 1, know how the file system of iDevices can be accessed; 2, aren't afraid of doing so. Note that unless you edit other files than I describe, my fix is absolutely safe.
The AppStore update list
However, the new version, surely by mistake, has removed the volume boosting setting. Volume boosting is of enormous importance if you watch videos in noisy environments – this is why I've been recommending (article on DSP's) the excellent player “It's Playing” for people who want their iDevices to be louder. And nPlayer's volume boosting implementation is flawless: it works just great even with hardware acceleration and even with iOS-native container files with iOS-native audio tracks. For example, my standardized M4V file with AAC audio (therefore, both iOS-native) HERE! The majority of players otherwise being able to apply volume boosting can't do this; the most known example of them being GoodPlayer.
This is how the global Settings looked in the previous two versions (1.8/1.9):
(iPad 4; click for larger image)
And this is how it looks in 1.10:
As you can see, the Boost menu is gone and is replaced by Dolby Mobile.
I'm still working on a full review of the app. (Let me tell you it'll be a really positive one. I REALLY love the latest versions of this player. Even very rarely supported features like full SSA subtitle support are here and work flawlessly.) Nevertheless, given that many users may be affected by this bug, I've found it necessary to publish an article on fixing it as quickly as possible.
Basically, if you aren't jailbroken, the solution will be pretty awkward. However, if you can keep the volume boost always enabled and aren't annoyed by the consequences (vastly decreased dynamic range), you can safely do it. If you did jailbreak your iDevice, you, of course, will have a much easier time.
If your iDevice isn't jailbroken
Then, your only way is using a desktop iOS file transfer tool like iExplorer and copy the file Apps/nPlayer/Library/Preferences/com.newin.nplayer.plist to your desktop:
then, edit the plist file in a plist editor. On a Mac, Xcode's default editor will work just fine; on a PC, you'll want to use plist Editor for Windows. You'll need to change Settings>AudioBoost from “1” to, say, “4” if you want 400 percent boost. Then, transfer the plist file back to your iDevice, making sure you first delete the file before the transfer and don't try to overwrite it.
(Editing the file in Xcode's plist editor on a Mac; click for larger image)
If your iDevice is jailbroken...
Than your life will be much easier – actually, particularly if you bookmark the home directory of the app, you can easily and quickly change volume boosting any time, without any desktop computer.
All you'll need is getting the absolutely excellent iFile, navigate to /Library/Preferences in the home of nPlayer, tap com.newin.nplayer.plist and select Property List Viewer from the list. Then, just tap Settings and, then, AudioBoost. Then, you can already modify its value:
A quick audio boosting tip
If you try to play back an iOS-native media file with an AAC audio track, make absolutely sure you switch to Hardware decoding from the default QuickTime. Otherwise, there won't be audio boosting. Feel free to test this with the video I've linked to above: there'll only be volume boosting if you do change the decoding mode. Let me present you with a mini-tutorial on this:
1, tap the Settings icon while playing back the video:
(click for larger image for all the three screenshots)
What about the future?
I've already contacted the devs on the matter. Hopefully they also fix it soon. In the meantime, feel free to use my fix.
EDIT (11/Apr/2013 8:30 GMT): nPlayer has been removed from the AppStore. This means the devs have received my mail and will release a fixed version soon. In the meantime, my fix continues to work on existing 1.10 installs.
EDIT (11/Apr/2013 17:30 GMT): I've talked to the developers of nPlayer.
1, the new, 1.11 version will soon be available. According to the devs, "we are expected to release the new version by the end of this week."
2, it will NOT support DTS any more. That is, should you want to play DTS files in the future, make sure you do NOT upate and/or backup the IPA installer o that you can return to the previous version easily!
3, version 1.10, in addition to the volume boosting bug I've discovered (and come up with a method of circumventing it), had some other problems as opposed to previous versions:
- there is a memory leak problem when you use the hardware decoding option
- and another bug in file cache when you stream video files. This bug causes a delay in loading file when streaming.
Let me repeat: do NOT update to the new, 1.11 version if you need to keep DTS support and can put up with the problems of 1.8/1.9/1.10!