CATV image quality subjective evaluation table

CATV Image Quality Subjective Evaluation Table
　　The subjective evaluation of the image quality at the user end adopts the five-level damage standard, which should be implemented in accordance with the five-level damage standard of Article 4.2 of the international GB7401. The 4-level image is the design standard of the CATV system.
Level Subjective evaluation of image quality damage (S/N) 5MHz (dB) CCIR (S/N)
5 points (excellent) No damage or interference is detected on the image 45.5 44.7
4 points (good) There is slightly perceptible damage or interference on the image, but it is not annoying 36.6 34.7
3 points (medium) There is obvious damage or interference on the image, which is annoying 29.9 30
2 points (poor) The damage or interference on the image is serious and quite annoying 25.4 27
1 point (poor) The damage or interference on the image is serious and cannot be watched 23.1 21

For the Chinese television standard C/N=N+6.4dB, image level 4 (S/N=36.6dB) corresponds to C/N=43dB.

The formula for the relationship between meter-weighted signal-to-noise ratio and image level
(S/N) 5MHz = 23-Q + 1.1Q2 (dB) (EBU experimental formula), (S/N) 5MHz refers to the meter-weighted signal-to-noise ratio measured within a 5MHz bandwidth
(S/N) 6MHz = 21-Q + 1.1Q2 (dB) (supplementary formula of the Ministry of Radio, Film and Television)