[FFmpeg-devel] [PATCH 1/8] libavcodec/jpeg2000_parser: Speed up long skips

[Tomas Härdin]

ons 2022-06-01 klockan 11:59 +0200 skrev Anton Khirnov:
> Quoting Tomas Härdin (2022-05-31 11:58:39)
> > 
> > 
> > From fedd7f9ae2c691a25c37be935d7547be61d46017 Mon Sep 17 00:00:00
> > 2001
> > From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= <git at haerdin.se>
> > Date: Fri, 20 May 2022 11:38:25 +0200
> > Subject: [PATCH 1/8] libavcodec/jpeg2000_parser: Speed up long
> > skips
> > 
> > ---
> >  libavcodec/jpeg2000_parser.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/libavcodec/jpeg2000_parser.c
> > b/libavcodec/jpeg2000_parser.c
> > index 2975e71482..9fac958dfa 100644
> > --- a/libavcodec/jpeg2000_parser.c
> > +++ b/libavcodec/jpeg2000_parser.c
> > @@ -95,6 +95,17 @@ static int find_frame_end(JPEG2000ParserContext
> > *m, const uint8_t *buf, int buf_
> >          state64 = state64 << 8 | buf[i];
> >          m->bytes_read++;
> >          if (m->skip_bytes) {
> > +            // handle long skips
> > +            if (m->skip_bytes > 8) {
> > +                // need -9 else buf_size - i == 8 ==> i ==
> > buf_size after this,
> > +                // and thus i == buf_size + 1 after the loop
> > +                int64_t skip = FFMIN(m->skip_bytes - 8, buf_size -
> > i - 9);
> > +                if (skip > 0) {
> > +                    m->skip_bytes -= skip;
> > +                    i += skip;
> > +                    m->bytes_read += skip;
> 
> Shouldn't you also update state(64)?
> 

It gets updated after 8 more skips. Keep in mind the buffer may end
before the skip is fully done, so I can't just AV_RB64().

/Tomas