[keehun]

The parent comment referred to "keyframes" instead of just "frames". Keyframes—unlike normal frames—encode the full image. That is done in case the "delta" you mentioned could be dropped in a stream ending up with strange artifacts in the resulting video output. Keyframes are where the codec gets to press "reset".

[account42]

> That is done in case the "delta" you mentioned could be dropped in a stream ending up with strange artifacts in the resulting video output.

Also to be able to seek anywhere in the steam without decoding all previous frames.

[seeknotfind]

Oh right. For non realtime, if you're not IO bound, this is better. Though I'd wonder how portable the codec code itself would be.

[actionfromafar]

The encoder has a lot of freedom in how it arrives at the encoded data.