When a file is encrypted, the only way to access it is to decrypt it first using an application to pull from the decrypted file. Assuming that encryption was used in the first place to maintain security or limit access to sensitive information, decrypting it first before accessing it defeats the purpose of encryption in the first place. Even if the decrypted data is automatically deleted after being played, remnants of it are still existent in the disk and could be recovered.
A better solution is to have the application decrypt the file in memory leaving no trace of the encrypted data.
Read the rest of the guide here: http://www.codeproject.com/Articles/796587/Using-Encrypted-Files-Without-Decrypting-To-Disk