ffmpeg - 压缩算法能否同时无损和有损？

Question

我看到 ffmpeg 有一些编解码器(例如 H.264)，它们被定义为 同时无损和有损 ，据我了解，无损和有损是互斥的 :压缩算法要么丢失信息，要么不丢失。

怎么可能同时无损和有损呢？

运行ffmpeg -codecs 2>/dev/null| grep h264 ，我得到:

DEV.LS h264                 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 [...]

DEV.LS代表解码器，编码器，视频，不仅帧内压缩，有损压缩，无损压缩。

Answer 1

签到Wikipedia for H.264它说:

H.264 is typically used for lossy compression in the strict mathematical sense, although the amount of loss may sometimes be imperceptible. It is also possible to create truly lossless encodings using it — e.g., to have localized lossless-coded regions within lossy-coded pictures or to support rare use cases for which the entire encoding is lossless.