On Wed, Jun 28, 2023 at 7:34 PM Andreas Rheinhardt < andreas.rheinha...@outlook.com> wrote:
> Paul B Mahol: > > On Wed, Jun 28, 2023 at 11:57 AM Paul B Mahol <one...@gmail.com> wrote: > > > >> > >> > >> On Wed, Jun 28, 2023 at 11:11 AM Andreas Rheinhardt < > >> andreas.rheinha...@outlook.com> wrote: > >> > >>> Paul B Mahol: > >>>> On Wed, Jun 28, 2023 at 12:26 AM Andreas Rheinhardt < > >>>> andreas.rheinha...@outlook.com> wrote: > >>>> > >>>>> Paul B Mahol: > >>>>>> On Tue, Jun 27, 2023 at 11:45 PM Andreas Rheinhardt < > >>>>>> andreas.rheinha...@outlook.com> wrote: > >>>>>> > >>>>>>> Paul B Mahol: > >>>>>>>> On Tue, Jun 27, 2023 at 11:05 PM Andreas Rheinhardt < > >>>>>>>> andreas.rheinha...@outlook.com> wrote: > >>>>>>>> > >>>>>>>>> Paul B Mahol: > >>>>>>>>>> On Tue, Jun 27, 2023 at 9:47 PM Andreas Rheinhardt < > >>>>>>>>>> andreas.rheinha...@outlook.com> wrote: > >>>>>>>>>> > >>>>>>>>>>> Paul B Mahol: > >>>>>>>>>>>> Patch attached. > >>>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> Where do you intend to use this? What is the point of it? > >>>>>>>>>>> After all, using this value in GET_VLC makes no sense; only > >>>>>>> compile-time > >>>>>>>>>>> constants do. > >>>>>>>>>>> > >>>>>>>>>> > >>>>>>>>>> It works when used in ac-4 as get_vlc2. > >>>>>>>>>> > >>>>>>>>> > >>>>>>>>> Could you please define "works"? Using a non-compile-time > constant > >>>>> will > >>>>>>>>> not benefit at all; it will only lead to more runtime checks. > >>>>>>>>> > >>>>>>>> > >>>>>>>> I do not follow your worries. > >>>>>>>> I can not use compile time constant as its very complicated code. > >>>>>>>> > >>>>>>> > >>>>>>> Let's take a look at GET_VLC: > >>>>>>> #define GET_VLC(code, name, gb, table, bits, max_depth) \ > >>>>>>> do { \ > >>>>>>> int n, nb_bits; \ > >>>>>>> unsigned int index; \ > >>>>>>> \ > >>>>>>> index = SHOW_UBITS(name, gb, bits); \ > >>>>>>> code = table[index].sym; \ > >>>>>>> n = table[index].len; \ > >>>>>>> \ > >>>>>>> if (max_depth > 1 && n < 0) { \ > >>>>>>> LAST_SKIP_BITS(name, gb, bits); \ > >>>>>>> UPDATE_CACHE(name, gb); \ > >>>>>>> \ > >>>>>>> nb_bits = -n; \ > >>>>>>> \ > >>>>>>> index = SHOW_UBITS(name, gb, nb_bits) + code; \ > >>>>>>> code = table[index].sym; \ > >>>>>>> n = table[index].len; \ > >>>>>>> if (max_depth > 2 && n < 0) { \ > >>>>>>> LAST_SKIP_BITS(name, gb, nb_bits); \ > >>>>>>> UPDATE_CACHE(name, gb); \ > >>>>>>> \ > >>>>>>> nb_bits = -n; \ > >>>>>>> \ > >>>>>>> index = SHOW_UBITS(name, gb, nb_bits) + code; \ > >>>>>>> code = table[index].sym; \ > >>>>>>> n = table[index].len; \ > >>>>>>> } \ > >>>>>>> } \ > >>>>>>> SKIP_BITS(name, gb, n); \ > >>>>>>> } while (0) > >>>>>>> > >>>>>>> If max_depth is not a compile-time constant, then the compiler will > >>> have > >>>>>>> to perform both of the max_depth > 1 && n < 0 checks; yet, this is > >>> not > >>>>>>> useful: If the depth of a particular VLC is (say) 1, then none of > the > >>>>>>> possible bits read will lead to reloading at all, because the n < 0 > >>>>>>> condition will never be true; the only reason this condition exists > >>> is > >>>>>>> to use a compile-time upper bound, so that one can eliminate the > >>> reload > >>>>>>> code (and in particular, avoid the runtime checks). > >>>>>>> > >>>>>>>> Works means that vlc code is extracted correctly. > >>>>>>>> > >>>>>>> > >>>>>>> If you have no upper bound about max_depth and it works, then use > 3. > >>>>>>> > >>>>>> > >>>>>> It does not work to use 3 all the time. And that one never worked in > >>> any > >>>>>> codec so far. > >>>>>> > >>>>> > >>>>> I just ran FATE with the check for max_depth removed from GET_VLC and > >>>>> from read_vlc for the cached API (effectively setting max_depth to 3 > >>>>> everywhere). It passed. So it "works" (but in a suboptimal way). At > >>>>> least it does if you have ordinary VLCs (created by the vlc.c > >>>>> functions). Are you doing anything special with them or so? > >>>>> > >>>> > >>>> FATE code coverage is very limited. > >>>> > >>>> Also I do not follow your reasoning about this added field at all. > >>>> > >>>> What is calculated over and over again in each get_vlc2() call? > >>>> > >>> > >>> Nothing is calculated over and over again in each get_vlc2() call; but > >>> if you use a non-compile-time constant, then the check for max_depth is > >>> performed in each get_vlc2() call, even though it is unnecessary. > >>> > >> > >> So what? > >> Nothing use this yet. So it does not matter. > >> > > > > As already written, cant use compile time constant at all, as there are > > many codebooks with different size and max depth. > > And codebooks are picked by other parameters, and max depth differs even > > between same codebooks set. > > max_depth only needs to be a upper bound of the actual max_depth. You do > not need the real max_depth. > > > And using 3 always is not efficient and also may not work reliably all > the > > time. > > > > I have already told you why I believe the opposite to be true for the > first statement and why I don't understand your second statement at all. > You have not given any counterarguments to my points. Please show your > code. > Please show your version of auto max depth calculation that can make you happy. > > - Andreas > > _______________________________________________ > 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".