F4V is a well-known flash video format developed by Adobe System. It is supported by Adobe Flash Player. Currently, approximately 80% of online videos are transmitted using Adobe Flash technology. Files with the F4V extension are called a container format. The F4V format, in comparison with other files of the FLV category, uses boxes to store information. In addition to devices with an operating system from Apple, these files can play almost all browsers that support flash video playback. F4V files resemble .FLV files, but use “blocks” to store data. Examples of blocks that are supported by the F4V format include meta block (metadata), moov block (file header), ftyp block (requested player tools), uda block (user data in free form), etc. The format container, in the development of which the ISO Media File Format was used, initially used the Quick Time Container Format from Apple. Compared to the old FLV format, the F4V format is fully compatible with the h.264 and ACC formats. This provides an opportunity to use other container formats.
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.