[Libav-user] qmin qmax qscale settings when encoding always from raw yuv frames

["René J.V. Bertin"]

On Jan 17, 2013, at 11:52, Harald Jordan wrote:

> first problem for me. The input for an encoder is anyway always a decoded frame, so it always has the “perfect” quality. So assumed we always want to have the best available quality, basically the assumption that the qscale settings depend on your input is not correct, right?

Not exactly, I think - at least not for input that is decoded from a lossy compression method. It is my experience (using existing software, not tweaking qmin/qmax/qscale) that such re-encoding such frames with too high a quality setting can be counterproductive. I think of it as exaggerating the (de)compression artefacts that can result in a file size increase rather than decrease.

> Now, when I write an encoder using libavcodec that is always fed from yuv422p pictures, what sense do those settings make?

Control the level of detail in (and the size of) your encoded content, I presume?

R