On Wed, 24 Apr 2024 16:48:54 +0530 Gyan Doshi <ffm...@gyani.pro> wrote: > > > On 2024-04-24 04:21 pm, Niklas Haas wrote: > > As discussed in my previous series for fixing scale2ref[1], this filter > > is fundamentally broken, and the only real fix would be to switch to > > activate(), or ideally FFFrameSync. > > > > [1] https://ffmpeg.org//pipermail/ffmpeg-devel/2024-March/323382.html > > > > The main thing making this difficult is the fact that scale2ref also > > wants to output ref frames to its secondary output, which FFFrameSync > > does not support, and which is ultimately at least part of the root > > cause of trac #10795. > > > > Since this is in principle completely unnecessary (users can just > > 'split' the ref input and have it be consumed by vf_scale), and to make > > the design of this filter a bit more robust and maintainable, switch to > > an approach where vf_scale itself gains the ability to reference > > a secondary input stream, using the "ref_*" series of variables. > > > > This makes the current [i][ri]scale2ref[o][ro] equivalent to the only > > slightly more verbose [ri]split[t][ro]; [i][t]scale=rw:rh[o]. (And > > conversely, it is no longer necessary to use nullsink to consume an > > unused [ro]) > > In principle, a good idea, but how does this impact memory use and speed > in the not-so-uncommon scenario where multiple overlay targets are > scaled 2 ref and then overlaid > e.g. > > in current flow: > > [a][base]scale2ref[a][ref]; > [b][ref]scale2ref[b][ref[; > [c][ref]scale2ref[c][ref[; > [d][ref]scale2ref[d][ref[; > [ref][a]overlay[ref]; > [ref][b]overlay[ref]; > [ref][c]overlay[ref]; > [ref][d]overlay[ref]; > > in new flow: > > [base]split=5[base][refa][refb][refc][refd]; > [a][refa]scale[a]; > [b][refb]scale[b]; > [c][refc]scale[c]; > [d][refd]scale[d]; > [base][a]overlay[outa]; > [outa][b]overlay[outb]; > [outb][c]overlay[outc]; > [outc][d]overlay[out]; > > > Regards, > Gyan
I have not tested it exactly, but based on my understanding of libavfilter it shouldn't affect memory usage at all. `split` does not duplicate frame data, it merely creates more references. And since all of the `overlay` filters are upstream of [out], they all consume both of their inputs before any forward progress can be made. So there is no filter in this graph that can buffer more than 1 frame. Actually, I would suspect memory usage to be slightly *lower* on average, because ff_filter_activate_default() first consumes all possible frames from input 1, then all possible frames from input 2, etc.; whereas FFFrameSync consumes from both inputs simultaneously. > > _______________________________________________ > 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". _______________________________________________ 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".