Lesson topic: « ».
Lesson objectives: 1. To introduce children to the concepts of "digital sound", "ADC", "DAC", "microphone", "audio adapter".
3. To give students a general idea of the principles of operation of a tape recorder, phonograph, etc.
4. to form the ability to create sound files using the "sound recording" program
5. Develop logical thinking and memory;
6. Cultivate interest in the subject, respect for
COMPUTER.
Equipment:Multimedia equipment, board, presentation, tasks for practical work, stereo headphones with microphone, textbook.
Lesson plan:
Organizing time
Checking d / z (frontal survey)
Explanation of new material
Summarizing
During the classes:
Organizing time.
Greeting students. Attendance check.
Checking d / z
What is multimedia?
Name the areas of application of multimedia.
What is the difference between a multimedia training program and a training video?
What are the advantages of multimedia applications in education over the traditional form of education?
Explanation of new material.
The topic of today's lesson is: Analog and digital audio. Technical means multimedia ».
At the end The famous American inventor Thomas Edison made a phonograph in the 19th century.
How the phonograph works
Speech, music or singing create sound vibrations that are transmitted to the recording stylus of the phonograph. The needle, acting on the surface of a rotating wax roller, leaves a groove on it with varying depth - a sound track. When playing sound, the reverse process occurs: the movement of the reading needle along the sound track is accompanied by its oscillations with the same frequency. These vibrations are converted by the phonograph into an audible sound.
Edison's phonograph is the first sound recording device in history.
In the middle In the 20th century, an electrophone appeared - an electrical analogue of a gramophone.
Analog sound representation
The soundtrack of a phonograph record is an example of a continuous form of sound recording.
This form is called analog. In an electrophone, the vibrations of a needle moving along a sound track are converted into a continuous wave. electrical signal.
IN In the 20th century, the tape recorder was invented - a device for recording sound on magnetic tape. It also uses an analog form of sound storage. Only now soundtrack- this is not a mechanical "groove with pits", but a line with a continuously changing magnetization. With the help of a reading magnetic head, an alternating electrical signal is created, which is sounded by the acoustic system.
Sounds- air vibrations - in the microphone of the tape recorder turn into electric current vibrations. The current creates fluctuations in the magnetic field, which are "imprinted" on a tape coated with a thin layer of iron powder. This way of writing is called analog: one type of oscillation turns into another, similar one. The sound is reproduced in the same way, but only in reverse: the magnetized tape, moving, causes the appearance of an electric current, which, after amplification, enters the speakers and makes them sound.
digital audio- representation of an analog audio signal in the form of a bit sequence that corresponds to the levels of electrical sound vibrations at certain intervals of time. To convert audio to digital form, pulse code modulation or, less commonly, sigma-delta modulation is used. In addition to describing sound vibrations in digital form, the creation of special commands for automatic playback on electronic musical instruments is also used, the clearest example of this technology is MIDI.
Sound is recorded through a microphone, which creates a continuous electrical signal, and playback is through speakers, which also sound under the action of a continuous electrical signal. How do these devices work with discrete data in computer memory? There is a transformation of the analog form of sound representation into a discrete and inverse transformation. The first process is called analog to digital conversion(ADC), the second - digital-to-analog conversion(DAC).
Microphone used to input sound into the computer. The continuous electrical vibrations coming from the microphone are converted into a numerical sequence. This work is done by a device connected to a computer called audio adapter or sound card.
The reproduction of sound recorded in computer memory also occurs with the help of an audio adapter that converts digitized sound into an analog electrical signal. audio frequency coming to acoustic speakers or stereo headphones.
Scheme of the passage of sound from a source through a microphone, ADC, processor, DAC, loudspeaker and again into sound
Recording and playback of video films on a computer, as well as working with sound, are associated with the DAC-ADC conversion. For these purposes, there are special video input/output cards. Video frames digitized and stored in computer memory can be edited.
optical CDs.
Sound, video, graphics combined in a multimedia application require large amounts of memory. Therefore, for their storage, sufficiently capacious and, preferably, inexpensive media are needed. These requirements are met optical CDs. Digital video discs have the largest information capacity.
Consolidation of new material (frontal survey)
What are the first audio playback devices you know?
What is the definition of digital audio?
What is ADC and DAC
Give examples technical devices, in which sound is stored and played back in analog form.
In what technical systems Is the sound transmitted in analog form?
Why can the form of sound representation in a computer be called discrete and digital?
Why are CDs used to store multimedia applications?
Why are special I/O cards used to work with video?
What is the purpose of a multimedia projector?
Practical work at the computer
How to record sound with Sound Recorder
1. Make sure you have an audio input device, such as a microphone, connected to your computer.
2. Open the Sound Recorder component. To do this, click the Start button. In the search box, type Sound Recorder, and then select the Sound Recorder component from the list of results.
3. After launching the Sound recorder program, it appears on the screen working window containing a recording scale and several buttons resembling the controls of a conventional tape recorder (Fig. 1). To record sound, you need to perform a number of preparatory steps. First of all, you need to determine the source of the sound. To do this, open the program window Volume control(Volume Control), on the taskbar. In the window that appears, check the boxes to disable all devices except the one you need, for example, a microphone. Next, you should return to working with the recording program and adjust the recording quality for the phonogram.
To work with multimedia applications on a computer, special hardware and software
Microphone used to input sound into the computer. The continuous electrical vibrations coming from the microphone are converted into a numerical sequence. This work is done by a device connected to a computer called audio adapter , or sound card . The reproduction of sound recorded in computer memory also occurs with the help of an audio adapter that converts digitized sound into an analog audio audio frequency electrical signal supplied to acoustic speakers or stereo headphones . It follows from the above that the sound card combines the functions of a DAC and an ADC. Rice. 1.3 illustrates the described process.
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| Rice. 1.3. Audio conversion on input and output |
Recording and playback of video films on a computer, as well as working with sound, are associated with the DAC-ADC conversion. For these purposes, there are special video input/output cards . Video frames digitized and stored in computer memory can be edited.
To demonstrate multimedia applications to a large audience, use multimedia projector . Such a projector transfers to big screen image from the monitor screen.
Sound, video, graphics combined in a multimedia application require large amounts of memory. Therefore, for their storage, sufficiently capacious and, preferably, inexpensive media are needed. These requirements are met optical CDs (CD - Compact Disk). Along with a large capacity (about 700 MB), they have reliable protection against data loss. Currently, CD-ROM and CD-RW discs are widely used. have the highest information capacity digital video discs - DVD. On a modern DVD can store up to 20 GB of information. This is enough to accommodate a full-length movie with high-quality sound.
Questions and tasks
1. What are the elements sound card responsible for the reproduction of digital and synthesized sound?
2. Why are CDs used to store multimedia applications?
3. Why are special I/O cards used to work with video?
4. For what purpose is a multimedia projector used?
The source of the video signal is most often an analog device - a television tuner, VCR, camcorder. A special digital FireWire port is used to transfer digital video (for example, a signal from digital video cameras) to a computer. However, digital video cameras are not yet widely used. Therefore, for computer signal processing of analog video devices, it is necessary to digitize them, i.e., convert from analog to digital form. This requires I/O cards that accept the incoming analog video signal and digitize it in real time, then this data must be stored on the hard disk. After saving the digitized image, it is edited. These functions are performed by the video capture device.
A video signal capture device - a video blaster (VideoBlaster) is a video card, also called an image capture device, a video input device, a TV grabber (Grab - capture), image capturers (Image Capture - image capture), and provides:
Receiving a low-frequency video signal (from a video camera, tape recorder or TV tuner) to one of the software-selectable video inputs;
Displaying the received video in real time in a scalable window of the Windows environment (a VGA monitor can be used instead of a TV);
Freezing a frame of a digitized video;
Saving the captured frame on a hard drive or other available storage device as a file in one of the accepted graphic standards (TIP, TGA, PCX, GIF, etc.).
A generalized diagram of a device of this type is given in Fig. 4.22.
The video decoder receives a signal from one of the inputs, digitizes it, digitally decodes it according to the television standard, and transmits the received YUV data to the video controller.
The video controller performs the organization of digitized data streams between the elements of the video card, performs the necessary digital data conversions (for example, YUV to RGB, scaling), organizes their storage in its own memory buffer, transfers data over the computer bus when stored on the hard drive, and also transfers them to a digital-to-analog converter.
The digital-to-analog converter, together with the video controller, participates in the formation of a “live” TV window on the monitor screen, performs an inverse analog conversion of a digital captured image, and transmits a signal from a video adapter or an RGB signal from a memory buffer to the monitor.
When choosing a video blaster card, it is necessary to take into account its main indicators:
frame resolution in the saved video stream;
the possibility and types of hardware compression (compression) of video information in real time;
the possibility of simultaneous input of video and audio information. N
The most common video blaster cards are:
mass entry-level cards;
semi-professional;
entry-level professional cards;
professional.
Mass entry level cards Capable of capturing and storing on a hard drive a video stream with a frame resolution not exceeding 352 x 288 pixels, although twice the resolution is possible to store individual frames. There is no hardware video compression, therefore, when working with such cards, it is necessary to use a special program - an encoder, which allows real-time compression of a video stream using the MPEG-1 or MPEG-2 algorithm. There is no sound input in devices of this class, which requires a separate sound recording through the sound card input.
semi-professional cards provide a resolution of 768 x 575 pixels, corresponding to the standard for PAL video; support the simplest type of hardware video compression M-JPEG, which reduces the volume occupied by a digitized film by 100 times. However, these cards do not have a sound input.
Entry level professional cards have an audio input, which allows you to simultaneously record to the hard video disc sound accompaniment; provide hardware compression of the M-JPEG type and can be used not only for input, but also for output of an edited video from a PC to a VCR. The latter allows you to store movies on a regular video cassette when using a computer as a timeline.
Professional cards have the possibility of hardware compression using the MPEG-1 or MPEG-2 algorithm with a reduction in the volume of the digitized film by 200 times.
After editing and editing, the video can be re-recorded on an analog video cassette using the video input of the same card, or subjected to even more severe compression using the MPEG-4 algorithm for subsequent recording on a CD-R.
| 7 classes | Lesson planning for the academic year (textbook by I.G. Semakin and others) | Technical means of multimedia
The main topics of the paragraph:
Sound input/output system;
- devices for working with video frames;
- media storage devices.
Acquired Skills and Skills:
Sound recording.
- Video recording.
- Add sound to the presentation.
- Adding a video image to the presentation.
- Creation of hyperlinks and transition buttons (in the absence of the ability to work with sound and video).
To work with multimedia applications on your computer, you need special hardware and software.
The microphone is used to input sound into the computer. The continuous electrical vibrations coming from the microphone are converted into a numerical sequence. This work is done by a device connected to the computer called an audio adapter, or sound card. The reproduction of sound recorded in computer memory also occurs with the help of an audio adapter that converts digitized sound into an analog electrical audio signal that is fed to acoustic speakers or stereo headphones. It follows from the above that the sound card combines the functions of a DAC and an ADC. Figure 5.3 illustrates the described process.
Recording and playback of video films on a computer, as well as working with sound, are associated with the conversion of the DAC - ADC. For these purposes, there are special video input / output cards. Video frames digitized and stored in computer memory can be edited.
A multimedia projector is used to demonstrate a multimedia application to a large audience. Such a projector transfers the image from the monitor screen to a large screen.
Sound, video, graphics combined in a multimedia application require large amounts of memory. Therefore, for their storage, sufficiently capacious and preferably inexpensive media are needed. These requirements are met by optical compact discs (CD - Compact Disk). Along with a large capacity (about 700 MB), they provide reliable protection against data loss. Currently, CD-ROM and CD-RW discs are widely used (see § 6). Digital video discs - DVD - have the largest information capacity. On a modern DVD can store up to 20 GB of information. This is enough to accommodate a full-length movie with high-quality sound.
To work with sound, a microphone, a sound card and speakers (speakers or headphones) are used.
Analog video must be digitized before processing on a computer.
CDs are used to store multimedia applications, containing large amounts of information.
DVDs are designed to store full-length movies with high-quality sound.
1. What elements of a sound card are responsible for recording sound into a computer and for its acoustic reproduction?
2. Why are CDs used to store multimedia applications?
3. Why are special I/O cards used to work with video?
4. For what purpose is a multimedia projector used?
Create a presentation "Museums of Russia" consisting of the following slides:
1 slide.
Title: Museums of Russia
Slide drawing:
Transition to the next slide: automatically after 1 second.
2 slide.
Title: Viktor Vasnetsov
Slide drawing:
3 slide.
Title: Levitan Isaac Ilyich
Subtitle: Tretyakov Gallery
Slide drawing:
Transition to the next slide: automatically after 3 seconds.
4 slide.
Title: Rembrandt Harmenszoon van Rijn
Subtitle: The Hermitage
Slide drawing:
Transition to the next slide: automatically after 3 seconds.
5 slide.
Title: Rafael
Subtitle: The Hermitage
Slide drawing:
Choose a design template, slide layout and design yourself,
- be sure to add musical accompaniment (background sound),
- Mandatory use of the WordArt object (at least in one slide),
- Mandatory use of animation effects (at least 3 types).
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