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. > > - 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".