This seems to consist of 1.2.3 and 1.2.7. This structure, where meeting one success criterion automatically means meeting another, is rather confusing.
Add a clear explanation of relationship among related SCs, either in the WCAG or in the UW.
The success criteria are written as clearly as we know how. There are only two general techniques for making multimedia accessible to the blind: Audio Description (AD) and Full Text Alternatives. Either technique is acceptable for Level A WCAG 2.0 conformance. Audio Description is required for Level AA. Both techniques are required for Level AAA. This is a case where higher-level success criteria build upon the requirements of lower-level success criteria with the intention of having cumulative, progressively stronger, requirements.