h. Audio/Video formats in mobile phones:

      1. MPEG (Motion Picture Experts Group): It is wide range of formats for digital audio and video files. The most common among them are MPEG-4 (for video) and MP3 (for audio). An audio storage protocol that stores music in a compressed format with very little loss in sound quality. MP3 is the most common MPEG format for audio files. MP3 files can be played using the music player of the mobile phone or set as a ringtone.

      2. MPEG-4 is one of the latest video/audio compression method standardized by MPEG group, designed specially for low-bandwidth (less than 1.5MBit/sec bitrate) video/audio encoding purposes.MPEG-4 is designed to deliver DVD-quality video (MPEG-2) at lower data rates and smaller file sizes.

The official filename extension for MPEG-4 Part 14 files is .mp4, thus the container format is often referred to simply as MP4. However various file extensions are also commonly used to indicate the content inside the MP4 container:

      a.  MPEG-4 files with audio and video generally use the standard .mp4 extension.

      b. Audio-only MPEG-4 files generally have an  .m4a extension. This is especially true of non-protected content.

      c. MPEG-4 files with audio streams encrypted by FairPlay Digital Rights Management as sold through the iTunes Store use the .m4p extension.

      d. Audio book and podcast files, which also contain metadata including chapter markers, images, and hyperlinks, can use the extension .m4a, but more commonly use the .m4b extension. An .m4a audio file cannot "bookmark" (remember the last listening spot), whereas .m4b extension files can.

      e. Raw MPEG-4 Visual bitstreams are named .m4v.

      f. Mobile phones use 3GP, a simplified version of MPEG-4 Part 12 (MPEG-4/JPEG2000 ISO Base Media file format), with the .3gp and .3g2 extensions. These files also store non-MPEG-4 data (H.263, AMR, TX3G).

3. AAC (Advanced Audio Coding)

AAC is a file format for storing digital audio. It's commonly used for storing music on the Internet, PCs and portable music players and phones. It is similar to MP3, but it was designed to be its successor and offers better quality and smaller file sizes. It also supports DRM, which enforces copyright. AAC+ and AAC++ are newer versions of the standard.

4. AIFF (Audio Interchange File Format)

It is a file format developed by Apple and company to store audio information. This is a really old file format compared to MP3 and is very similar to the WAV file format developed by Microsoft. The most major difference between the AIFF and MP3 is compression. AIFF does not do compression while MP3 does.

5. 3GP and 3G2 are multimedia container formats used for the delivery and playback of audio/video files over high-speed wireless networks, especially mobile cell phones. Developed and defined by the 3rd Generation Partnership Project and 3rd Generation Partnership Project 2 respectively, they are built to contain various types of compressed data. Both the 3GP and 3G2 file formats were especially designed so as to decrease the bandwidth and storage requirements in order to accommodate mobile cell phones. Structurally, they are based on the ISO file format defined in ISO/IEC 14496-12-MPEG-4 Part 12. The 3GP file can store video streams in MPEG-4 Part 2 (also called H.263) and MPEG-4 Part 10 (AVC/H264) formats, and audio streams in AAC-LC, HE-AAC v1, HE-AAC v2, AMR-NB, , and AMR-WB+. The 3G2 file, on the other hand, can store all the video streams as those of 3GP. As for the audio streams, it can store the same as those of 3GP, with the exception of HE-AAC v2 and AMR-WB, which it cannot store.

Instead, it can store EVRC, EVRC-B, EVRC-WB, QCELP, SMV, and VMR-WB audio streams. The 3G2 Timed Text specifications are also more advanced than those of the 3GP.

3GP and 3G2 files can be opened on most 3G enabled mobile phones, and some 2G and 4G devices as well. File size, memory, and resolution limits may vary from phone to phone. When transferred on the computer, the files should be converted to more popular video formats.

i. Single SIM Phones V/s Dual SIM phone:

SIM stands for Subscriber Identity Module card that which is the key for the portability of your mobile. The SIM from a mobile service provider will be able to secure your data and identify yourself over the networks card stores all the connection data and identification numbers you need to access a particular service provider.

Single SIM mobile phones are those that use only a single SIM at a time, and dual SIM mobile phones are those that can operate on two SIM cards. In dual SIM card mobile phones, if one of the SIM card remains inactive while the other one isactive, then is known as Standby Dual SIM phone, and if both the cards are active concurrently, then is known as Active Dual SIM mobile phone.

Advantages of single SIM over dual SIM:

1. The price charge of a Dual SIM phone goes much higher than usual, and in comparison, having a basic phone on the other SIM is much cheaper than having a Dual SIM, which comes with the disadvantage of paying more.

2. You will be switching off both the SIM when you want to switch the mobile off. Therefore, this is much better two have two single SIM phones, that you have the option of being on in one when the other goes off, or the battery goes down in one or the other, you will always be available in one or the other phone

3. A dual SIM mobile phone battery must be of larger capacity than a normal phone. Some phones support two separate batteries one for each SIM card. While this improves talk and standby time, second battery certainly adds to the handset weight.

Advantages of dual SIM over single SIM:

1. The main overall advantage that you get with dual SIM phone, is the fact that you can have two separate numbers register for the same phone

2. Freedom of choice for service providers.

3. Most dual SIM phones are made to work worldwide, so long as they are set up for the right type of connection.In some countries only one type of phone network is present. That means service providers are only compatible with either GSM or CDMA.  But as long as you have dual SIM cards that are compatible with that type of signal, you can access wireless service from just about anywhere in the world, which is a massive advantage.

4. A Dual SIM mobile phone is handy for those who often travel between two countries. They don’t have to change their SIM card while traveling.

5. The Dual SIM phone also gives peace of mind to those who dread the thought of being out of a network. It allows one to have two numbers from two different carriers, which minimizes the risk of losing the signal bar – if one carrier signal goes weak there is an option to try the other.

6. Technological limitations are much lesser in Single SIM phones.

Fig shows a phone with dual SIM slots