[FFmpeg-devel] high bitdepth support and the location of the zero padding

Wilbert Dijkhof wilbertdijkhof at yahoo.com
Sun Sep 4 15:55:25 EEST 2016

Hi all,
I hope this is the right place for this question. If not i hope you can point me to a place where they can help us with further.
We have a question about the high bitdepth support (10/12/14 bitdepth) in ffmpeg.To support those formats in AviSynth, we need to know whether the zero padding is located in the MSB or in the LSB.If we look at the source code of ffmpeg, the zero padding seems to be located in the MSB (see Avisynth+). That's correct right?
The followup question is, is this required by the specs (say h.264/h.265 for example)? If so where is it described in the specs (i looked at the h.264 specs, but couldn't find anything about it). If not, how does the decoder/renderer know that that the zero padding is located in the MSB?

We were a bit confused, because in the high bitdepth formats described by Microsoft (see https://msdn.microsoft.com/en-us/library/windows/desktop/bb970578(v=vs.85).aspx), the zero padding is located in the LSB. We hope someone can shed us some insight into this.

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