 Welcome to the session of mp3 player learning outcome of the session. Before proceeding, let me ask you one question. So where the mp3 files are commonly used? You can pause the video, think about the question and write down your answer in your notebook. After writing the answer, return to the video to see the answer. Let me give you the answer. Commonly used mp3 files are in CD player, DVD player, computers and the internet audio. They are used for the audio storage. So what is the mp3? The mp3 stands for mpeg layer 3 is coding format for the digital audio. The mp3 is an example of the digital technology by which the sound you hear are stored in form of the numerical data. The key to store the music in a digital format is processor which is called as a sampling. You can think the mp3 as a computer file and the mp3 player as a special type of the computer which is used for playing back the sounds which are stored in a coded format inside the mp3 file. The loss data compression is used for encoding the mp3 file. The mp3 file works by reducing the accuracy of the certain information in a sound by considering the psychoacoustic analysis in which the sound which is beyond the hearing capability of the humans are discarded. Let us see the mpeg layer 3 audio coding and how it is done. The operating modes in the mpeg 3 audio coding is the mpeg 1 audio works for both mono and stereo audio signal. The technique which is called as a joint stereo encoding can be used to achieve the more efficient combiner coding of the left and right channels of the stereophonic audio signal. The layer 3 allows both mid and side stereo coding and the intense stereo coding also. Later it is specially helpful for the low beat rates but it bears the risk of changing sound image. The operating modes in the mp3 are single channel, a dual channel in which the two independent channels are used to stereo the stereo which is without joint stereo coding and the joint stereo coding. Next, the sampling frequency in mp3 encoding. The mpeg audio compression works on the number of different sampling frequencies. The mp3 one defines the audio compression at 32 kilohertz, 44.1 kilohertz and 48 kilohertz. The mpeg to extend this to the half rates that is 16 kilohertz, 22.05 and 24 kilohertz. The mpeg 2.5 is the extension to the layer 3 which introduced the sampling frequency of 8 kilohertz, 11.05 kilohertz and the 12 kilohertz. Beat rates which is used in mpeg3 audio coding. The mpeg audio does not work at fixed compression ratio. The selection of beat rate of compressed audio is within some limit is completely left to the implementer or the operator of the mpeg audio coder. For the layer 3 standard defines the range of the beat rates from 8 kilo bit per second to the 320 kilo bits per second. Furthermore, the layer 3 decoders must support switching of beat rates from audio frame to the audio frame. The combined with the beat reservoir technology, this allows both variable beat rate coding and a constant beat rate coding at the fixed values within limits which is tested by the standard. So, how the mpeg3 music is stored in a computer file as a .mp3 file. Basically, inside the mpeg3 file a music is stored as a long string of beats which are nothing but the series of chunks which are called as a frames. Each frame starts with the header and followed by the music data itself. At the start of mpeg3 file there is a kind of index card that stores the details regarding to the track information. This information is called as a metadata and each part of is stored in which which is called as a id3 tag. So, here is the mpeg3 frame where it starts from the metadata that is information about the information about the audio which is stored in the mpeg3 file, mpeg3 header and the mpeg3 data. The mpeg3 header consists of the four fields and it is of totally 32 bit. Let us see each and every bit in detail. A field consists of 11 bits and the positions of these bits are from 31 to the 21st. These are used as a frame synchronization bits. The b bit fields consist of two bits and its position is at 20 and 19. It is used in order to give the mpeg audio version id such as 00 is identified as mpeg version 2.5, 01 is reservoir, 10 is identified as a version 2. And the 11 stands for the mpeg version 1. The c field consists of two bits and it is positioned at 18 and 17. And it provides a layer description such as 00 is for reserve, 01 is for layer 3, 10 is for layer 2 and 11 is for the layer 1. Next is the d bit field. The d bit consists of only one bit and it is positioned at 16th position. So, it is used as a protection bit. So, 0 stands for it is protected by the CRC check and 1 stands for not protected. The next sign or the next field is a e field which consists of the 4 bits and the position is at 15 to 12. So, these fields shows us the bit rate index. For an example, 0000 stands for version 1 layer 1 mpeg format which is of the free. It is defined by the audio composer within a certain range. 0000 stands for 32 bit for V1 and L1 version and it is also 32 bit for V1 and L2. And for version 2 layer 2 and layer 3 file it is of the 8 bit. The 0010 in which bit rate is 64 for version 1 layer 1, 48 for version 1 layer 2, 40 for version 1 layer 3, 48 for version 2 layer 1 and 16 for version 2 layer 2 and layer 3. Similarly 11, it has 96 for version 1 layer 1, version 1 layer 2 has a 56 and version 1 layer 3 has a 48 bit rate and the version 2 layer 1 has 56, version 2 layer 2 layer 3 has 24 bits. As so on 1100 has 448 bit rate for version 1 layer 1, version 1 layer 2 has 384 bit rate and version 1 layer 3 has 320, version 2 layer 1 has 250, 256 and version 2 layer 2 and layer 3 has 160 bit rate. 1111 stands for a bad bit rate means it is not allowed. F field it is of the 2 bit and it is positioned at 11 and 10. It defines the sampling rate frequency index. For example, if the bit is 00 it defines 44100 hertz sampling rate, frequency rate is used for MPG 1, MPG 2 for that bit 22 kilo hertz sampling index is used and the MPG 2.5 has 11 kilo hertz and for the bit 00 MPG 1 has 44 kilo hertz. For 10 MPG 1 has 32 kilo hertz, MPG 2 has 16 kilo hertz and MPG 2.5 has 8 kilo hertz. 11 is reserved for all the fields. G field, the G field consists of 1 bit, it is at 9th position and it introduce the padding bits which is used for the adjusting the frame length. 00 stands for there is no padding bits are used, one stand for the padded bits are used in a one extra slot. The edge field it is of also 1 bit, it is positioned at 8th position, it is a private bit, this one is used for informative only. The next a field is the eye field. The length of this field is 2 bit and it is positioned as 7 and 6th and this define the channel mode. That means 00 stands for stereo, 01 stands for joint stereo, 10 stands for dual channel that is 2 mono channels and 11 stands for single channel that is mono. G field consists of 2 bits, it is positioned as 5th, 5th and 4th and these are used for the mode extension that is used in joint stereo only. So, layer 1 and layer 2 for 00, band 4 and 2, 31 is used and band 8 to 31 is used and 1, 0, the band 12 to 31 is used. This field K it is of 1 bit and it is positioned at 3rd position and it is used for the copyright information. 0 means the audio is not copyrighted and 1 stands for the audio is copyrighted. The real field it is of 1 bit and the position data at 2nd and it is used for the original in or not. 0 stands for copy of the original media and 1 stands for the original data that is audio is the original. M field it is of 2 bit, it can position at 1 and 0. It is used as a emphasis 00 stands for no emphasis, 01 stands for 50 by 15 millisecond emphasis, 10 and 11 are reserved. Let us see the block diagram of the mp3 player. The figure shows the typical block diagram of the JP 200 mp3 player. As you can see it consists of DSP processor, digital signal processor and the microcontroller unit. These are the two main units of the mp3 player. The microcontroller take the data which is stored into the flash memory as a mp3 file for the decoding and the data is given for the decoding from the digital signal processor. The digital signal processor processes on that data and then decoded data is given to the digital to analog converter. The digital to analog converter convert that digital data into the analog and amplify it and given to the headphone. In this way we listen the audio from the mp3 player. In case of the recording the data is recorded in two ways from the mic also and from the audio jack input also. When this data is coming this data is in analog. So analog to digital converter convert that data into the digital domain. Data is sampled and given to the digital signal processor. The DSP processor works on that sample data, adjust the bitrates and give encoded data is given to the microcontroller. Now the microcontroller will save that data into the flash memory. In this way the data is recorded and played back into the mp3 player. LCD display is used in order to display what current song is played. The FM status of the FM radio and ATC. The USB connector is also present here which is used in order to upload the data to the computer from the mp3 player or to copy the data from the computer to the mp3 player by means of the microcontroller unit. So these are the references of the session. Thank you.