On Thu, Sep 06, 2018 at 01:10:31PM -0300, James Almer wrote: > On 9/4/2018 5:09 PM, Michael Niedermayer wrote: > > On Mon, Sep 03, 2018 at 10:29:13AM -0300, James Almer wrote: > >> On 9/3/2018 5:17 AM, Michael Niedermayer wrote: > >>> On Sun, Sep 02, 2018 at 09:34:23PM -0300, James Almer wrote: > >>>> From: Luca Barbato <lu_z...@gentoo.org> > >>>> > >>>> Merged-by: James Almer <jamr...@gmail.com> > >>>> --- > >>>> This is the next merge in the queue. It's a critical part of the AVFrame > >>>> API, > >>>> so even if FATE passes I'd rather have others look at it and test in case > >>>> something breaks. > >>>> > >>>> The only difference compared to the libav commit is the "32 - 1" padding > >>>> per > >>>> plane when allocating the buffer, which was only in our tree. > >>> > >>> why is the STRIDE_ALIGN (which is a thing in units of bytes along the > >>> horizontal axis) added to padded_height which is vertical axis ? > >>> This is not done prior to the change > >> > >> The only way to keep this padding we currently have in the tree applied > >> to the buffer allocation for each plane like it was before the change > >> (Except it'll now be one continuous buffer instead of one per plane) is > >> by passing it alongside the height parameter to > >> av_image_fill_pointers(). The result is essentially the same. > >> > >> Do you want me to change the name of the variable, or remove it and pass > >> 32 - 1 to both av_image_fill_pointers() calls directly? Removing the > >> padding will probably just make whatever overreads prompted its addition > >> to resurface. > >> Alternatively, i can just no-op this merge and move on. > > > > allocating one plane instead of 3 is better obviously so i dont think this > > should be no-oped unless someone implements this differently > > > > i dont think the padding can be removed saftely but i might be missing > > something > > also i do not remember this 100% > > > > what i see and i may have misunderstood your reply but the code before > > places > > a few bytes between planes, the new code places a few lines, that is alot > > more > > space. Its not even the best that can be done with the current API. For > > example > > the number of extra lines would generally be 1 to provide sufficient padding > > at most reaslistic resolutions. > > > > also there is the independant question on the API, do we want/need to make > > adding padding between planes easier?> > > actually i think that if we change from 31 bytes to X lines padding then > > this > > should be a commit seperate of the 3->1 change. This would make bisect much > > more meaningfull and its rather trivial to split this. > > Do you have a suggestion on how to choose how many lines of padding to > add?
something like (with rounding up) bytes * horizontal_chroma_subsampling / width * vertical_chroma_subsampling > And how would it be done? Just passing (h + padding_lines) to > av_buffer_alloc() pre merge, and to av_image_fill_pointers() post merge? possible > > It would also be faster if you could commit that change instead. thinking of this, its maybe simpler to adjust data[*] by these to get exactly teh same effect as before thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB In a rich man's house there is no place to spit but his face. -- Diogenes of Sinope
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