Re: [FFmpeg-devel] [PATCH] MULTI VLC decoding boost

[Paul B Mahol <onemda@gmail.com>]

On Fri, Sep 15, 2023 at 12:01 AM Michael Niedermayer <michael@niedermayer.cc>
wrote:

> On Mon, Aug 28, 2023 at 07:36:17PM +0200, Paul B Mahol wrote:
> > Patches attached.
> >
> > Thanks for kurosu for pointing unmerged branches.
> >
> > The UNCACHED_PATH for x86_32 is broken with this for 2 codecs it touches.
> > Fix is trivial, to be fixed later.
> [...]
>
> > +int ff_init_vlc_multi_from_lengths(VLC *vlc, VLC_MULTI *multi, int
> nb_bits, int nb_elems,
> > +                                int nb_codes, const int8_t *lens, int
> lens_wrap,
> > +                                   const void *symbols, int
> symbols_wrap, int symbols_size,
> > +                                   int offset, int flags, void *logctx)
> > +{
> > +    VLCcode localbuf[LOCALBUF_ELEMS], *buf = localbuf;
> > +    uint64_t code;
> > +    int ret, j, len_max = FFMIN(32, 3 * nb_bits);
> > +
> > +    ret = vlc_common_init(vlc, nb_bits, nb_codes, &buf, flags);
> > +    if (ret < 0)
> > +        return ret;
> > +
> > +    multi->table = av_malloc(sizeof(*multi->table) << nb_bits);
> > +    if (!multi->table)
> > +        return AVERROR(ENOMEM);
> > +
> > +    j = code = 0;
> > +    for (int i = 0; i < nb_codes; i++, lens += lens_wrap) {
> > +        int len = *lens;
> > +        if (len > 0) {
> > +            unsigned sym;
> > +
> > +            buf[j].bits = len;
> > +            if (symbols)
> > +                GET_DATA(sym, symbols, i, symbols_wrap, symbols_size)
> > +            else
> > +                sym = i;
> > +            buf[j].symbol = sym + offset;
> > +            buf[j++].code = code;
> > +        } else if (len <  0) {
> > +            len = -len;
> > +        } else
> > +            continue;
> > +        if (len > len_max || code & ((1U << (32 - len)) - 1)) {
> > +            av_log(logctx, AV_LOG_ERROR, "Invalid VLC (length %u)\n",
> len);
> > +            goto fail;
> > +        }
> > +        code += 1U << (32 - len);
> > +        if (code > UINT32_MAX + 1ULL) {
> > +            av_log(logctx, AV_LOG_ERROR, "Overdetermined VLC tree\n");
> > +            goto fail;
> > +        }
> > +    }
> > +    ret = vlc_common_end(vlc, nb_bits, j, buf, flags, localbuf);
> > +    if (ret < 0)
> > +        goto fail;
> > +    return vlc_multi_gen(multi->table, vlc, nb_elems, j, nb_bits, buf,
> logctx);
> > +fail:
> > +    if (buf != localbuf)
> > +        av_free(buf);
> > +    return AVERROR_INVALIDDATA;
> > +}
>
> this is copy and pasted from
>
> int ff_vlc_init_from_lengths(VLC *vlc, int nb_bits, int nb_codes,
>
> leading to code duplication, it would be better if you could
> factor the duplication out
>
> thx
>

-1


>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
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>
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