Old Custom Codecs are not compatible with the latest player v1.7.31.
DTS is a type of audio codec which is owned and copy righted by DTS Inc. You can use dts pass through without any copy right issue. But, in mobile it needs to be down sampled to 2 channels which is a conversion process and it needs to the permission from DTS Inc.They are not ready to have a deal with the software players. So, dts playback support is dropped from the official MX-Player. Simply if your video has dts audio it wont play any audio. Only video will be played. So, Ktsamy [Senior XDA Member] have re-compiled the ffmpeg sources with dts audio support for our MX-Player lovers.

Announcement:
Now this project is migrated to XDA-DevDB. You can download the codec files from download tab. For mobile users I will provide the direct links in this post as well. You can follow the project by clicking on Follow button. The followers will get the notification whenever the new version is updated.

Also see: [Guide] How to Backup and Restore Settings in MX Player
Instructions:
Download one of the following codec according to your platform as mentioned in the player (Go to Settings 》 Decoder 》 Download Custom Codec. Here the you can find the codec type). If you are not sure then download the all in one pack (AIO)

ALL DOWNLOAD LINKS HERE: http://idroidhorizon..com/2014/10/MX-Player-Custom-Codec.html


Arm v7-Neon
Arm v7-Tegra3
Arm v7-Tegra2
Arm v6 VFP
Arm v6
Arm v5TE
x86
MIPS
AIO Pack

Check the hash values to ensure the file integrity.
Open MX Player on your device.
Go to Settings 》 Decoder 》 Custom Codec
Navigate into the folder you have saved the file. It will show the downloaded zip file.
Select the zip file. If you have selected the right zip file MX Player will Automatically restarts else it will revert with error ("Can't find custom codec for this version".
If you have multiple codecs in a single file (AIO version), it will automatically load the right codec for your device
Once Player restarts check whether the codec is in use or not in Settings 》Decoder 》Custom Codec. (If the path of zip is shown here, then you have successfully loaded the codec.)
If you want to play DTS while using HW decoder,
Then go to Settings 》Decoder
Enable software audio. By this the Video will be rendered by HW and audio will be rendered by SW+

XDA:DevDB Information
MX Player Custom Codec, Tool/Utility for the Android General

Contributors
ktsamy, bleu8888

Version Information
Status: Stable
Current Stable Version: 1.7.31
Stable Release Date: 2014-08-23

Windows Media Player can't play the file (or can't play either the audio or video portion of the file) because the required codec isn't installed on your computer.
Windows Media Player error C00D10D1: DTS audio decoder
Applies to these editions of Windows 7
Missing codec: DTS audio decoder
Then I searched a Windows blu-ray player which can play DTS, DO NOT need any DTS audio decoder.