On Mon, 2022-08-01 at 02:14 +0000, Soft Works wrote: > > -----Original Message----- > > From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of > > Xiang, Haihao > > Sent: Monday, August 1, 2022 3:53 AM > > To: ffmpeg-devel@ffmpeg.org > > Subject: Re: [FFmpeg-devel] [PATCH v3 2/2] ffmpeg_opt: consider HW > > acceleration method when selecting decoder > > > > On Fri, 2022-07-29 at 09:46 +0000, Soft Works wrote: > > > > -----Original Message----- > > > > From: ffmpeg-devel <ffmpeg-devel-boun...@ffmpeg.org> On Behalf Of > > > > Ronald S. Bultje > > > > Sent: Friday, July 29, 2022 10:50 AM > > > > To: FFmpeg development discussions and patches <ffmpeg- > > > > de...@ffmpeg.org> > > > > Subject: Re: [FFmpeg-devel] [PATCH v3 2/2] ffmpeg_opt: consider > > > > HW > > > > acceleration method when selecting decoder > > > > > > > > Hi, > > > > > > > > On Fri, Jul 29, 2022 at 4:38 PM Xiang, Haihao < > > > > haihao.xiang-at-intel....@ffmpeg.org> wrote: > > > > > > > > > libdav1d is the preferred AV1 decoder in FFmpeg, libdav1d is > > > > always > > > > > > > > used > > > > > when > > > > > running the command below even if user expects vaapi or other > > > > HW > > > > > acceleration > > > > > methods. > > > > > > > > > > > > > I think that is a pretty serious issue. Don't we always want to > > > > prefer a hw > > > > decoder by default? I agree there should also be ways to force- > > > > select > > > > specific hw/sw decoders, but shouldn't hw be the default? > > > > > > I don't think that this would be reasonably possible in any way. > > > There are a lot of questions which ffmpeg cannot answer, e.g.: > > > > > > - Which hwaccel to choose? > > > - Which hwaccel is available? > > > - Which parameters are required for selecting a device > > > that is working? > > > - Is the auto-selected device even capable to decode a certain > > > input? > > > (pixel format, bit depth, codec profile, frame size, ...) > > > > > > For the user who is creating the command line, it is important to > > > be able to rely on what is going to happen. If they can't command > > > lines will fail: > > > > > > - The outputs of hw decoders vary. Some output to hw format, some > > > to sw format by default. You may need to specify > > > > hwaccel_output_format > > > or use hwdownload > > > - Depending on the hwaccel, a totally different set of filters > > > may be required (not to speak of encoders) > > > - How would you specify that you want a sw decoder instead? > > > > > > IMO, predictability is the topmost important behavioral aspect > > > for users (be it humans of machines.. ;-) > > > > > > I agree with you it would be better not to make hw the default if > > user doesn't > > ask for. However '-hwaccel arg' is used to specify hw acceleration > > method in the > > examples. According to doc ( > > https://github.com/FFmpeg/FFmpeg/blob/master/doc/ffmpeg.texi#L1260- > > L1262), a hwdecoder is expected. > > > > "@item -hwaccel[:@var{stream_specifier}] @var{hwaccel} > > (@emph{input,per-stream}) > > Use hardware acceleration to decode the matching stream(s). " > > > > This patch is to fix the issue that a SW decoder is chosen even if > > user is > > expecting a hw method, not to make hw the default in any case. > > > > Thanks > > Haihao > > > > Oh, I'm in no way opposed to your patch, I just talked about the > idea of a general automatic selection of hardware decoders. >
Sorry for misreading your email and thanks for your clarifying. > I agree that the behavior for AV1 should be the same as for the other > decoders. Thanks, I will push it if no more comment in a few days. - Haihao _______________________________________________ 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".
