Overview: Video compression

Video compression represents pictures efficiently through coding choices, prediction and constraints on the resulting stream.

Compressed video carries instructions for reconstructing pictures, not necessarily a complete independent image for every moment. The relationships among predicted pictures influence seeking and error recovery, while profiles and levels describe constraints on the stream. Lossy and lossless topics establish what is preserved before those structural choices are examined.

• How video compression works
  Video compression represents picture information with fewer bits by exploiting patterns and, in lossy modes, accepting approximation.

• Lossy video compression
  Lossy video compression reduces data by allowing the reconstructed pictures to differ from the encoder input.

• Lossless video compression
  Lossless video compression reproduces the picture samples supplied to the encoder exactly.

• Picture prediction and random access
  Picture prediction creates dependencies that determine how video can start decoding at a requested point.

• Codec profiles
  A video codec profile constrains the coding tools and sample formats a stream may use.

• Codec levels and tiers
  Codec levels and tiers describe resource limits that a compatible decoder must satisfy.