File extension | .m4r |
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File category | Audio |
Stands for | MPEG-4 PART 14 for iPhone ringtones |
Developer | Apple Inc. |
Overview | M4R is one of the extensions of MPEG-4 Part-14 and it is specially designed by Apple for iPhone ringtones. It is just the relabelling of AAC and M4A. This extension provides an excellent quality of ringtones for iPhones and the size of the ringtone is also small. There are certain steps that one needs to follow for the conversion of any song into this format (iPhone ringtone). Firstly, select any song of 30 seconds and covert it to AAC format using iTunes. Then rename this file using .m4r extension. Finally, by using the iTunes transfer your ringtone file to iPhone. This can be done by connecting your iPhone to the computer and syncing the playlist. Now a user can easily use this ringtone for phone ring, alerts, alarms etc. It should be noted that these files will be supported only by the latest version. Hence, use the current version of iTunes. |
Technical description | It uses a lossy compression algorithm to encode the ringtones that is same as AAC and MP3 eareensions. But it has the additional feature of auditory masking which means it neglects other sounds which can be detected or recognized while listening or hearing another sound. It only discards the information which is surplus for the human ear. This results in good quality of iPhone ringtones. It takes less storage space without affecting the quality of audio. It is also a segment of MPEG-4 standard and this is stated in the ISO-IEC standard 14495-3. |
Links | wikipedia.org (opens in new tab - official documentation) |
File extension | .avi |
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File category | Video |
Stands for | Audio Video Interleave |
Developer | Microsoft |
Overview | This file format stores both audio and video files for playback purposes. It is used to store files that are of high quality as file compression is less in this extension. Windows OS uses this as the default format to store multimedia files but other operating systems such as Linux, Unix and Mac also support this. The data in it is encoded by various codecs such as DivX and XviD. There is a variety of software that support these files. For instance- Microsoft Movies & TV, Windows Media Player and Apple QuickTime player; etc. Due to its low compression ability, it is widely used to make short movies, promos and advertisements; etc. It should be noted that AVI format result in large files that is why it is rarely used for video streaming. |
Technical description | In AVI extension, file's data is divided into blocks or chunks as it is a sub-format of RIFF(Resource Interchange file format). An identification of each chunk is done by FourCC tag. File header and metadata of video(like height, width and frame rate) are identified by ‘hdrl tag' which is sub-chunk and it is mandatory. There is one another chunk which is also obligatory that is ‘movi tag' and it has actual audio or video data. The last sub-chunk is ‘idx1 tag' and it records the offsets of the data chunks. This ‘idx1 tag' is completely optional. There is one limitation of this format that it does not contain variable bitrate data. |
Links | wikipedia.org (opens in new tab - official documentation) |