M4A to OPUS
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| - Information about M4A |
| Id |
| 4 |
| File extension |
| m4a |
| File category |
| Audio |
| Stands for |
| MPEG-4 PART 14 or MPEG-4 Audio |
| Developer |
| Apple |
| Overview |
| It is an audio file which uses AAC (Advanced Audio Coding) compression. Also, it is one of the formats of MPEG-4. It should be noted that MPEG-4 codec is used both for video and Audio. But M4A is specially designed by Apple for audio files only that is why it is used to store audiobooks, podcasts and songs. As sound files are encoded using AAC compression and this results in a reduction of file size and it also produces a very good quality of audio. Whenever somebody purchases music from the iTunes store then it is always available in this format. Many believe that MP4 and M4A are similar extensions, however, it’s not the truth. MP4 files can store both Audio and video files whereas the other one is entirely made for Audio files. |
| Technical description |
| These files are improved version of MP3 as it has the ability to store data without any loss. The audio files are completely reversible that is they can be inverted to their original copies with the same size. Besides this, these files does not have copyright protection whereas MP4 files are protected and they use DRM(Digital Rights Management) technology to enforce this protection policy. Due to this, one can copy these audio files effortlessly. These files have come with advanced features which include smaller sample block sizes, perception-based compression and bigger block sizes in stationary signals. There are a number of applications that support this extension. For example:- Microsoft Windows Media Player, VLC Media Player, Quicktime player, Microsoft Zune and Apple iTunes etc. |
| Links |
| wikipedia.org |
| - Information about OPUS |
| Id |
| 9 |
| File extension |
| opus |
| File category |
| Audio |
| Stands for |
| Ogg OPUS |
| Developer |
| Xiph.Org |
| Overview |
| It is a format for audio files which compresses the audios using lossy compression. It neglects the redundant information which can not be processed by the human ear. Internet Engineering Task Force (IETF) has standardized this format. It has superseded the Vorgis and Speex. It offers low latency i.e. there is a less delay in the signal when it enters the system and when it emerges out, this results in real-time interactive communication like video conferencing. Due to its good audio quality, it is widely used by in various listening tests. |
| Technical description |
| OPUS has good compatibility with low-end embedded processors as it is less complex. Ranging from 6kbps to 510kbps, it can support both variable and constant bitrate coding. Also, the frame size from 2.5ms to 60ms is supported by this codec. It works smoothly and maintains stability (by avoiding the distortion) while mixing of packets from distinct streams. Speech, Hybrid and pure-CELT are the three different methods used for encoding the audios of varied frequencies. For compressing the Speech up to 8kHz, SILk is used which is an audio compression developed by Skype Limited. The next mode, Hybrid uses CELT to compress the audio files above 8kHz frequency or for wider bandwidth and frame sizes 10ms and 20ms are supported by this mode. CELT(Constrained Energy Lapped Transform) is an open and free audio compression format which is especially used in communication that requires low latency. For general audio, the last mode pure-CELT is used. CELT is used for frame sizes which are less than 10ms. |
| Links |
| wikipedia.org |
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