An SPX file is a Speex audio file saved within an Ogg Vorbis container. Speex is an open source patent-free audio format designed for speech compression. It supports variable bitrate (VBR) encoding and several features not found in other audio codecs. Some examples include embedded encoding, intensity stereo encoding, and voice activity detection.

Speex

Is the most common format for storing audio. Almost any player on any platform can open mp3 files. The audio is compressed with loss of quality, but the loss is negligible for the typical user, and the file size is usually less than that of the original files.

MP3 Audio Format

This format was originally created as an alternative to mp3. The idea was to achieve a small file size with better sound quality. The first versions weren’t quite successful, but with the development of AAC, it became possible to store sound with less loss of quality, and with the same file sizes as that of mp3.

Advanced Audio Coding

This is open lossless codecs, developed under the Ogg project. Lately it’s become quite popular: many users wishing to store audio with original quality choose FLAC. This is partly in connection with the fact that codecs uses IDv1 and IDv3 tags - this allows a user to sort an audio collection according to one’s particular tastes, changing the original metadata of the tracks.

Free Lossless Audio Codec

Is a recording format, designed for use in movie theaters. Who is a direct competitor of Dolby Digital. It is used to accompany the film with the movie, as well as on optical video discs. It supports two modes of audio: 5.1 and 7.1, allows full bit rate in high end home theaters.

Digital Theater Systems

MP2 is a lossy audio compression format developed by MPEG (Moving Picture Experts Group). It is widely used for audio broadcasting, while MP3 is more common for desktop and online programs. The format is supported only by some audio players, so you may need to convert it to a more popular one like MP3.

MPEG-1/2 Audio Layer 2

This format was originally intended for voice compression and is able to change the bit rates of encoded audio data. AMR is actively used for encoding and decoding voice while its being transmitted over network channels. The format allows one to consider network capacity and adapt it to channel loads. Due to this, the voice quality is practically undiminished.

Adaptive Multi Rate

FLV is a Flash Video container used on popular hosting sites that stores audio, video and other data. It often uses h.264 or h.263 codecs for video storage and MP3 for audio. There are a lot of programs for both Windows and Mac operating systems that are able to open .flv files.

Flash Video

MP4 is an extension defined by MPEG-4 video standard and AAC audio standard. It is a container that supports all kinds of media such as video, audio, subtitles, 2D and 3D graphics. It is possible to open MP4 file with almost any player on Windows but on Mac you should use a plug-in or just convert the file to another format.

MPEG-4 Part 14

AVI is a multimedia container that is very popular among PC and Mac users. The format was developed by Microsoft in 1992. Usually AVI is used as a video format but unlike other formats of that time, AVI may contain both audio and video data compressed with a use of different combinations of codecs. More often such video codecs as DivX and XVID are used with .avi files. For audio playback such codecs as MP3, AC3 and PCM are used. It is possible to play AVI files with Windows Media Player or other similar programs.

Audio Video Interleave

DivX is a progressive implementation of the MPEG-4 format. It offers a significantly higher degree of video compression (comparing to another H.263 video codecs) and carries a number of revolutionary innovations of that time. To playback DivX files on PC, you can use many different programs because currently most video players support DivX even in FullHD resolution. For viewing such files in modern browsers the company developed DivX Web Player. However, the H.263 standard (which DivX implements) was created in 1996 and is currently considered obsolete. It was replaced by the H.264 and H.265 standards that are implemented in more progressive codecs such as HEVC and AV1.

DivX Networks

MKV is an open source container that can contain media data compressed with a use of different codecs. It has a lot of advantages over the legacy AVI container: it can contain audio tracks and subtitles in different languages, that can be switched without stopping the playback, file seek and rewind are very fast. Also the format is easy to edit, that is why audio and video data can be extracted effortlessly.

Conversions	Count
SPX to MP3	2
SPX to AAC	1
SPX to FLAC	1
SPX to DTS	1
SPX to MP2	0
SPX to AMR	0

Conversions	Count
AAC to SPX	17
MP3 to SPX	6
DTS to SPX	1
FLAC to SPX	1
MP2 to SPX	1
FLV to SPX	1
MP4 to SPX	1
AVI to SPX	0
DIVX to SPX	0
MKV to SPX	0

spx

Speex

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