Bet Some Of You Don’t Know Solution To CD And DVD File Recovery

Brief Introduction to Optical Storage


CD DVD file recovery 1 Optical storage, also known as optical disk data storage, is a primary method for storing electronic document. There are uneven pits and flats on the surface of optical disc, so different reflection is generated after light shines on them. Then, the different refection turns into the digital signal of 0 and 1 to accomplish optical storage.

Optical disc uses optical information as the storage carrier to store data. It is the optical storage medium developed in modern times and different from magnetic storage medium. Text, sound, graphics, image, animation and other multimedia data can be saved in an optical disc.

Optical disc is mainly divided into CD, DVD and Blu-ray disc according to stricter and the first two are very popular among users, especially music lovers. Though those three kinds of discs have difference in structure, the main structure principle is the same. In this paper, we’ll concentrate on CD and DVD. Users who want to know more about Blu-ray disc may as well turn to other articles.

Structure of Optical Disc


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CD structure: CD is short for Compact Disc. The commonly seen CD is very thin and its thickness is only 1.2mm. The parameters of CD are:
3-inch disc: outer diameter – 80mm, inner circular hole – 15mm, groove ring diameter –33.6mm (there’s little difference between different discs and some of them even don’t have groove). Print size: outer diameter – 78mm, inner diameter – 38mm.

5-inch disc: outer diameter – 120mm, inner circular hole – 15mm, groove ring diameter –33.6mm (there’s little difference between different discs and some of them even don’t have groove). Print size: outer diameter – 116mm or 118mm, inner diameter – 38mm.

CD has five layers in physical, including a substrate, a recording layer, a reflective layer, a protective layer and a printed layer. Let’s talk about them briefly. CD DVD file recovery 3

1.Substrate: it is the carrier of all functional structures (such as groove). Made from polycarbonate (PC), it has many characteristics: excellent toughness, wide temperature range, good dimensional stability, weather resistance, non-toxic, etc.

Generally speaking, substrate acts as the physical enclosure of the entire disc. The thickness and diameter of CD substrate are respectively: 1.2mm and 120mm. Relying on the hardness of the substrate, CD can be taken and placed casually. In terms of substrate, there’s no difference among CD-ROM, CD-R and CD-RW.

2.Recording layer: it is also called the dye layer sometimes, and this is the place used to burn signals during burning process. Its main working principle is: coating the substrate with a layer of dedicated organic dye to be prepared for laser information recording. Since the reflectance is different before and after burning, the laser will read signal with different lengths, and then convert the signal to digital number 0 and 1, thereby reading the information from CD.

Three kinds of organic dyes can be found on current market: cyanine, phthalocyanine and AZO. Now, the one-time recording CD-R mainly adopts phthalocyanine. Laser will burn the organic dye coated to the substrate in the process of burning. Here, special attention should be paid to one thing: instead of organic dye, it is a certain kind of carbon material that has been coated to the substrate of a CD-RW.

3.Reflective layer: as the third layer of optical disc, it is an area used to reflect laser beam. It is made up of pure silver metal with a material purity of 99.99% and similar to the silver reflective layer of mirror. When light reaches this layer, it will be reflected back. In general, this is the reason why our optical disc can be used as a mirror sometimes.

4.Protective layer: it is used to protect the reflective layer and recording layer so as to prevent the signal from being damaged. As far as we’re concerned, this layer is made up from light-cured acrylic material. In addition, the DVD +/- R series on current market also requires a glued part.

5.Printed layer: it is actually the back of optical disc and used to print customer identification, capacity and other relevant information. In addition to that, it plays a role in protecting disc from being damaged.

DVD structure: DVD is actually the acronym of Digital Video Disc. It makes the audio-visual experience improved to a level that can’t be compared by VCD due to its theater-level audio effect, multi-voice, multi-subtitle and multi-angle support and powerful interactive feature. DVD adopts the high-definition compression algorithm of MPEG2. The signal source of original DVD is the digital Beatcam band converted from original film copy with up to 1000 lines, so it can easily reach the 520 lines of resolution.

Almost the entire audio portion of original DVD disc is recorded by the 5.1-channel digital surround sound mode (DOLBY DIGITAL 5.1, known as AC-3) or more advanced DTS compression algorithm. This is totally different from the previous simulation of two-channel stereo surround sound playback.

Some parameters of DVD: diameter – 120mm, thickness – 0.6mm per side, laser wavelength – 635 to 650 nm, NA (numerical aperture) – 0.6, light track pitch – 0.74 μm, minimum convex pit length – 0.4 μm, error-correcting code length – RS to PC, modify modulation – 8 to 16, surface utilization: 86.6 cm², number of bytes per sector – 2048 to 2060 bytes.

There are five kinds of common DVD formats:
CD DVD file recovery 4 1.D5 (single-sided and single-layer DVD): its capacity is about 4.7GB. This kind of DVD format uses one side to store information and makes the other be printed with film material to form a cover. The laser head starts from circular core and it will read data outwards all the way along the circumference. Compared to other types, D5 has a minimum amount of data storage capacity. Correspondingly, it has a high compression ratio and the audio effect and video effect are also affected.

2.D9 (single-sided and double-layer DVD): its capacity is about 8.5GB. Different from D5, D9 adopts two layers to store data. That is to say though only one side of D9 is readable, this side has two layers, so the capacity has been doubled. The data read mode of laser head in D9 is the same with that in D5. After all data in the first layer have been read, the laser head will automatically adjust its focus to penetrate the first layer and reach the second layer. At this time, it will read data stored in the second layer in the same way.

3.D10 (double-sided and single-layer DVD): the capacity is approximately 9.4GB. Both sides of D10 will save data at the same time and they’ll be marked as side A and side B. When users finish watching one side, they need to flip the disc in order to continue to watch.

4.D14 (double-sided and multi-layer DVD): the capacity approaches 13GB. D14 is used to record data in the way of two sides and three layers. The first side is double-layered while the second side is single-layered.

5.D18 (double-sided and double-layer DVD): it has a largest capacity of 17GB. D18 has a total of two sides and four layers to record data. Its compression ratio can be reduced to a minimum value and its effect is the most prominent.

All in all, the light track of optical disc is a spiral line. The center of optical disc is the lead-in area, which marks the start place of data recording. The next is the directory area and it describes the directory and structure of documents. Then here comes the main data area, which is starting from the center and going outwards. The last is the lead-out area representing the end of all information.

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How Optical Disc Works

Knowing the working principle of optical disc can help users understand how data can be saved and read and it is helpful for users to understand CD and DVD file recovery. Thus, users may find ways to recover files from CD and DVD all by themselves when necessary or they can comprehend the reason why data is lost.

No matter what kind of data (audio, video, photo, etc.) is stored in the optical disc, it has to be converted to digital number “0” and “1” to be read out. “0” and “1” corresponds to the pit and flat on the disc.

If light shines on the flats of disc, 70% to 80% of the light will be reflected. On the contrary, if the light shines on pits, it will not be reflected. Thus, the light signal will be converted to electric signal according to the reflection rate. When there’s physical damaged on the surface of disc, data can’t be read normally, of course, and the chance for CD and DVD file recovery is very small (it depends on the damage degree and damage part of disc).

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Well, optical disc drive is indispensable for the normal work of a CD or DVD. But what is it? Actually, an optical disc drive is composed of three parts; they are respectively mechanical device, electronic device and optical device. Its structure includes laser head, laser device, photoelectric detector, optical device, servo control system, and so on. They work together to make the data storage and data access to optical disc possible.

  • Laser head: it belongs to the read-out system. The laser beam comes from it will beat down on the concavo-convex reflective surface and the beam will be reflected by it. After that, the photoelectric detector will detect the existence of reflected laser beam and then convert it to electric signal. After the signal has been processed by the electronic circuit, signal encoding can be obtained. At last, we can get the data when the decoding process of code has been completed.

    The laser head is able to determine the focus error and optical tracking error by analyzing the laser beam signal reflected from disc reflective layer. Those errors will activate focus servo and radial light tracking servo to adjust laser beam to the optimum position.

  • Laser device: it is made up of laser diode, focusing lens and other components. The GaAs semiconductor laser device can emit a laser beam with a wavelength of 0.78μm and an output power of 0.5MW.

  • Photoelectric detector: photoelectric detection diode is responsible for converting the laser beam reflected from disc reflective layer to electric signal. It can detect where the laser beam is coming from by virtue of the strength of electrical signal. Then, focus error, light tracking error and speed error will be gained to activate servo to adjust them to appropriate value.

  • Optical device: it includes grating, laser beam splitter, magnifying glass and other components. Collimating lens turns the laser beam into cylindrical beam. Laser beam splitter makes the reflected beam beat down on photoelectric detection diode. Objective lens is driven by the voice coil to move upwards and downwards and along the disk radial trace. In this way, the laser beam focus will always fall on the light track.

  • Servo control system: there are three basic servo control systems in optical disc drive: focus servo system, radial light tracking servo system and disc rotation speed control system. The first system is used to realize automatic focus. The purpose of the second system is to make laser beam always fall on the disc light track. Obviously, the last one exists here to control the rotating speed of optical disc.

Protect Optical Disc Well to Avoid File Loss

Despite all the advantages it has, one biggest disadvantage of optical disc is it is relatively fragile. That is to say, a CD or DVD is easy to get damaged once it is not protected well. Therefore, special attention needs to be paid to weather, temperature, humidity, dust, water, fire, blot, oil stain, scratch, etc. Just do the best you can to protect CD or DVD from being damaged physically since as we have mentioned before, the optical storage data recovery after physical damage is hard to achieve.

In addition, there’s another kind of damage which can hardly be avoided – that is soft failure. Accidental deletion, virus invasion, sudden power outage and software conflict are belong to this category. But luckily, the CD and DVD file recovery from soft failure is an easy task. Users just need to obtain a powerful file recovery program.

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MiniTool Power Data Recovery is believed to be one of the best recovery programs for CD and DVD users to recover files from CD and DVD conveniently. The “CD/DVD Recovery” module in it is designed especially for CD and DVD file recovery as you can see from the name. Just open it and follow the instructions in each operating interface to carry out optical storage data recovery step by step under guidance. You’ll find the file recovery from CD and DVD after soft failure is just a piece of cake even for green hands.

Please feel free to get one if you’re stuck in CD or DVD file loss and we believe you’ll be surprised by its excellent performance after using.