Low jitter processing
The root cause of audio CD sound quality
problems is the jitter of the data on the disc. This causes an error in the data read by the player. Taiji backup is our measure
to deal with this problem under the existing conditions. This is a process of data low jitter . The Taiji servo system we
developed can effectively reduce the interference of data stream jitter and read CD disk data more accurately. The CD data
is CIRC decoded on a digital signal processor equipped with a low jitter clock. The erroneous data (industry standard: <
3%) caused by the quality of the disc, or the data that was scratched during the use of the CD disc, will be repaired after
passing through the CIRC decoder. The decoded data is stored in a buffer memory. The data is then CIRC and EFM encoded on
the digital signal processor and written to a recordable CD-R disc by a very low jitter recorder controlled by the Tai Chi
servo system.
Error rate
The CD industry is the data error rate for testing CDs using professional
equipment. It is more suitable for detecting the degree of data loss caused by the physical structure damage of the CD disk.
As a consumer product, CDs need to be used in consumer playback devices. It is necessary to find an error rate detection method
that is closer to actual use to improve the credibility and practicality of the test results.
Synchronization
signal
When the CD is finished, the sync signal is the only data on the disc that can determine if there is
an error. A sync signal is a signal that has a certain digit length and is inevitably present after a certain period of time.
There are two situations that can cause errors in the sync signal: 1) the quality of the physical structure of the CD, causing
the servo system to fail to extract the sync signal from the data stream; 2) the jitter of the data stream, causing the sync
signal to not appear at a certain time . In both cases, the servo system of the CD player will determine that the sync signal
is incorrect. This determination result is not affected by the correctness of the verification data. As long as we detect
the error rate of the sync signal, we can evaluate the overall quality of the CD disk including the jitter of the data stream.
Test
We use the method of measuring the error rate of the sync signal to indirectly evaluate the
probability of CD data errors. This test uses a consumer player and a counter to record the number of synchronization signal errors for the standard test CD
and the Taiji backup CD, respectively. The following result is obtained: the probability of an error in the Tai Chi backup
CD disc synchronization signal is 10.3% (15/146) of the original CD disc.
We tested some CDs (CD Jitter Test ) using a consumer player. The Tai Chi backup CD in playback, the data stream jitter is lower than the original CD.
We
also used some Tai Chi backup CDs to compare sounds with LP records. In this comparison, the song playback of the Taiji backup
CD can feel the singer has a more appropriate emotional expression, and the music can more appropriately express the mood
of the lyrics. This result is consistent with the difference in their technical indicators.
All music data has been
placed on the original CD. Tai Chi backup just rearranges this data using low-jitter technology. This helps the player to
read accurately. In principle, an audio CD can express sound more accurately. In actual use, to play this feature on the audio
CD, we still need to meet the basic conditions that the player can get the correct data. This is like the LP needs to have
an accurate needle pressure to maintain its soft sound.
Created by Chen
Last revision date: Aug-2019