ons 2022-12-14 klockan 18:08 +0100 skrev Tomas Härdin: > tis 2022-12-13 klockan 11:20 +0800 skrev zhilizhao(赵志立): > > > > > > > On Dec 12, 2022, at 23:27, Tomas Härdin <g...@haerdin.se> wrote: > > > > > > lör 2022-12-10 klockan 01:22 +0800 skrev Zhao Zhili: > > > > From: Zhao Zhili <zhiliz...@tencent.com> > > > > > > > > It's well known that mediacodec encoder requires 16x16 > > > > alignment. > > > > Use our bsf to fix the crop info. > > > > --- > > > > v3: don't change the dimension for AV_PIX_FMT_MEDIACODEC. It > > > > can > > > > have > > > > side effect. > > > > > > Looks like this silently crops? Is that really a good idea? We > > > usually > > > don't do stuff like that. For example codecs that require even > > > dimensions complain loudly then fail. > > > > It’s reasonable to require even dimensions. Require dimensions > > aligned > > to 16 is uncommon. Everyone will complain why 1080x1920 doesn’t > > work. > > > > A lot of apps just use aligned dimensions. Users have no control on > > these apps. It’s not the same with FFmpeg, users (developer or not) > > can specify the dimension directly. > > Wait a sec, I think I was misunderstanding what the code is doing. > FFALIGN rounds *up*. Does this mean you insert fake data in the > border > that then gets cropped away, meaning the original essence is still > "there"? That's a different thing and probably perfectly OK. > > I think we might want something for this inside lavf somewhere, so > that > encoders can signal dimension alignment requirements. Some containers > (MXF, MOV) support such cropping in a codec-agnostic manner. > > > > > If we don’t fix it, either: > > > > 1. Reject and fail directly. User complain why. > > 2. Accept and keep going. Sometimes it works, sometimes don’t. It > > depends on the device and get into a confused situation. > > > > I know there are getWidthAlignment()/getHeightAlignment() to get > > alignment info of codecs. The results are unreliable. The only > > reliable way I can find is don’t depends on those API and fix it > > by ourself. > > Given how temperamental MC seems to be a "belt and braces" approach > might be appropriate when dealing with it. Tell users (ffmpeg.c is a > user here) that dimensions must be aligned by 16x16 and then > automagically doing the required padding and cropping somewhere (lavf > or ffmpeg.c) feels like a decent solution.
Come to think of it this kind of 16x16 requirement is very common and is already being handled silently: it's the macroblock size for almost every DCT codec when using 4:2:0 subsampling. /Tomas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
