M4P is an Audio file format developed by Apple Inc. Files with the .m4p extension are audio files that are downloaded from the iTunes Music Store. These are files that are encoded using the AAC method. They are additionally protected by Apple "FairPlay" DRM. The M4P file format is an extended version of storage formats such as MPEG-4 Part 14 or MP4. The format was initially associated with Apple's Protected AAC files. Now, the M4P format uses the FairPlay DRM system, which does not provide the ability to copy data. She also needs to authorize the device using Apple iTunes software. An M4P file is an array of data that is protected by a DRM system. And in order to play the file, some actions are required that are aimed at authorizing the computer in Apple's iTunes system. The M4P format limits the number of computers on which a specific file can be played. This will require registration with Apple iTunes. This will be enough to immediately use five computers. In the event that you need to play the file on more than five computers, you will need another account. In this case, you will need to purchase the song that you selected from a new account. Then access to it on the other five devices will be open.
OPUS is an audio file that is encoded using the Ogg Opus format (lossy coding). It was created for online audio streaming, that is, in order to transmit sound through a global network. The format is being developed by the Internet Engineering Task Force (IETF) and Xiph.Org communities. Applies SILK codecs when used in Skype and CELT (from Xiph.Org), provides support for variable bitrate. Most often, the OPUS codec is used for video conferencing, game chats, VoIP telephony. OPUS is a free audio codec that has international standard status (IETF RFC 6716). Its main advantages are a low coding delay (from 2.5 to 60 ms) and its significant speed, an increased degree of compression of audio data with high-quality sound, as well as support for multi-channel audio (within 255 channels). In 2011, J. Skeglund of Google conducted two series of tests, during which OPUS coding and decoding were compared, taking into account the assessments of experts and ordinary listeners. Studies have shown that OPUS provides stereo music with the same quality as MP3 and better quality than G.719 64 kbps. OPUS offers great streaming capabilities with dynamic tweaking and very low latency. This is always high sound quality and excellent data compression. Full support for OPUS is provided by Mozilla applications. He is the key Skype audio codec.