Cable Snake Oil Antidote
🐑 phomchick Geoffkait: “Uh, but the two states are not (rpt not) accurately decoded. Not completely accurately, anyway. That’s why the Green Pen, painting CD tray and CD Treatments and vibration isolation and vibration control improve the sound.” Sorry, not true. CDs include error correction encoding and decoding to ensure that the 1s and 0s are accurately read. Green pens and anti vibration tweaks on CDs and players are a complete waste of time and money. >>>>>Hey, don’t be sorry. You’re welcome to your opinion. Even though it happens to be completely wrong. No offense intended. I’m come to accept the inevitable newbie backlash. No biggie. |
There is some math in this article, it may be over your head: https://en.wikipedia.org/wiki/Reed%E2%80%93Solomon_error_correction The result is a CIRC that can completely correct error bursts up to 4000 bits, or about 2.5 mm on the disc surface. This code is so strong that most CD playback errors are almost certainly caused by tracking errors that cause the laser to jump track, not by uncorrectable error bursts. |
First phase of CD: "Each audio sample is a signed 16-bit two's complement integer, with sample values ranging from −32768 to +32767. The source audio data is divided into frames, containing twelve samples each (six left and right samples, alternating), for a total of 192 bits (24 bytes) of audio data per frame 2nd stage: " This stream of audio frames, as a whole, is then subjected to CIRC encoding, which segments and rearranges the data and expands it with parity bits in a way that allows occasional read errors to be detected and corrected. CIRC encoding also interleaves the audio frames throughout the disc over several consecutive frames so that the information will be more resistant to burst errors. Therefore, a physical frame on the disc will actually contain information from multiple logical audio frames. This process adds 64 bits of error correction data to each frame. After this, 8 bits of subcode or subchannel data are added to each of these encoded frames, which is used for control and addressing when playing the CD. 3rd stage: " CIRC encoding plus the subcode byte generate 33-bytes long frames, called "channel-data" frames. These frames are then modulated through eight-to-fourteen modulation (EFM), where each 8-bit word is replaced with a corresponding 14-bit word designed to reduce the number of transitions between 0 and 1. This reduces the density of physical pits on the disc and provides an additional degree of error tolerance. Three "merging" bits are added before each 14-bit word for disambiguation and synchronization. In total there are 33 × (14 + 3) = 561 bits. A 27-bit word (a 24-bit pattern plus 3 merging bits) is added to the beginning of each frame to assist with synchronization, so the reading device can locate frames easily. With this, a frame ends up containing 588 bits of "channel data" (which are decoded to only 192 bits music). And if that is not enough: "The smallest entity in a CD is a channel-data frame, which consists of 33 bytes and contains six complete 16-bit stereo samples: 24 bytes for the audio (two bytes × two channels × six samples = 24 bytes), eight CIRC error-correction bytes, and one subcode byte. As described in the "Data encoding" section, after the EFM modulation the number of bits in a frame totals 588. On a Red Book audio CD, data is addressed using the MSF scheme, with timecodes expressed in minutes, seconds and another type of frames (mm:ss:ff), where one frame corresponds to 1/75th of a second of audio: 588 pairs of left and right samples. This timecode frame is distinct from the 33-byte channel-data frame described above, and is used for time display and positioning the reading laser. When editing and extracting CD audio, this timecode frame is the smallest addressable time interval for an audio CD; thus, track boundaries only occur on these frame boundaries. Each of these structures contains 98 channel-data frames, totaling 98 × 24 = 2,352 bytes of music. The CD is played at a speed of 75 frames (or sectors) per second, thus 44,100 samples or 176,400 bytes per second. And lots more even more complicated data stuff. Naturally I am not making the stuff up, I stole it from a Wiki entry. I remember back in the late 1980's reading a book which was all about the complexity of the CD. It had all that info about how CDs are encoded, and decoded. So CDs are not just some reading simple zeros and ones... They read really really complicated zeros and ones! (since yes indeed the transition (All transitions!) is a one, and all the others are zeros. And not pits are one and lands are the other. LOL. |
