MMF is the Yamaha SMAF sound file format developed for mobile devices. The MMF format is linked to SMAF (Synthetic Music Mobile Application Format) files. Many people know this format because they very often use it as ringtones in cell phones. Yamaha’s SMAF tools were developed primarily by Yamaha to provide audio files that users could use as unique ringtones for their mobile phones. However, then the format was slightly improved. Now such files are capable of storing information, graphic, as well as text. You can create an SMAF file using Yamaha SMAF Tools. It can also be saved in WAV or MID format. It’s not uncommon to confuse MMF and SMAF formats. The fact is that MMF are called file extensions. SMAF is called the file itself. The MMF file is identical to MIDI files. It is capable of supporting music playback and showing graphics. Due to the implementation of the image display function, SMAF files now have considerable potential in the mobile application market. This is because they can store high quality images when the file size is limited at the same time. Typically, the size of SMAF files is much smaller than files of other formats that can perform the same functions.
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.