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

["Tomas Härdin" <tjoppen@acc.umu.se>]

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ons 2022-06-01 klockan 18:23 +0200 skrev Michael Niedermayer:
> On Wed, Jun 01, 2022 at 06:21:19PM +0200, Michael Niedermayer wrote:
> > On Tue, May 31, 2022 at 11:58:39AM +0200, Tomas Härdin wrote:
> > > 
> > 
> > >  jpeg2000_parser.c |   11 +++++++++++
> > >  1 file changed, 11 insertions(+)
> > > 634546fb5a0eb281eea87ad7471c503f5bc9e8ab  0001-libavcodec-
> > > jpeg2000_parser-Speed-up-long-skips.patch
> > > From fedd7f9ae2c691a25c37be935d7547be61d46017 Mon Sep 17 00:00:00
> > > 2001
> > > From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= <git@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(+)
> > 
> > breaks
> > j2kref/codestreams_profile1/p1_04.j2k
> 
> [jpeg2000 @ 0x7fb0b8002600] Psot 66195 too big
> [jpeg2000 @ 0x7fb0b8002600] error during processing marker segment
> ff90
> Input #0, j2k_pipe, from 'j2kref/codestreams_profile1/p1_04.j2k':
>   Duration: N/A, bitrate: N/A
>   Stream #0:0: Video: jpeg2000 (JPEG 2000 codestream restriction 1),
> gray16le(12 bpc), 1024x1024, 25 fps, 25 tbr, 25 tbn
> [jpeg2000 @ 0x7fb0b8003240] unsupported marker 0x97C8 at pos 0x6F0
> [jpeg2000 @ 0x7fb0b8003240] Missing EOC Marker.
> [jpeg2000 @ 0x7fb0b8032280] unsupported marker 0x97C8 at pos 0x6F0
> [jpeg2000 @ 0x7fb0b8032280] Missing EOC Marker.
> [jpeg2000 @ 0x7fb0b8006280] Psot 66195 too big
> [jpeg2000 @ 0x7fb0b8006280] error during processing marker segment
> ff90

Took a while to figure out, but this is due to buf_size - i - 9 being
changed to unsigned because of the uint32_t. Try attached patch. The
rest of the set should work with it.

Can we roll these tests into FATE?

/Tomas

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From e6a35973456d132adc4ae87904dfb3c31eff0fd5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomas=20H=C3=A4rdin?= <git@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..34a5487e90 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
+                int skip = FFMIN(FFMIN((int64_t)m->skip_bytes - 8, buf_size - i - 9), INT_MAX);
+                if (skip > 0) {
+                    m->skip_bytes -= skip;
+                    i += skip;
+                    m->bytes_read += skip;
+                }
+            }
             m->skip_bytes--;
             continue;
         }
-- 
2.30.2


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