On Fri, Aug 09, 2019 at 07:29:50PM +0300, Nick Renieris wrote: > From: Nick Renieris <velocit...@gmail.com> > > Some JPEGs [1] have incorrect DHT entries that map 2 codes to > the same value. > > The second (last) mapping does not ever actually appear in the > code stream, therefore ignoring any mappings after the first one > fixes this. > > Without this, an "mjpeg_decode_dc: bad vlc: 0:0" error is thrown. > > --- > > [1]: Embedded JPEGs in "X7 RAW" and "X7 CinemaDNG" samples here: > https://www.dji.com/gr/zenmuse-x7/info#downloads > > Signed-off-by: Nick Renieris <velocit...@gmail.com> > --- > libavcodec/jpegtables.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/libavcodec/jpegtables.c b/libavcodec/jpegtables.c > index cbe5523cb4..6f596cfc92 100644 > --- a/libavcodec/jpegtables.c > +++ b/libavcodec/jpegtables.c > @@ -130,14 +130,27 @@ void ff_mjpeg_build_huffman_codes(uint8_t *huff_size, > uint16_t *huff_code, > { > int i, j, k,nb, code, sym; > > - code = 0; > + /* Zero-initialize huff_size (needed for multiple mappings check below) > */ > + k = 0; > + for(i=1;i<=16;i++) { > + nb = bits_table[i]; > + for(j=0;j<nb;j++) { > + sym = val_table[k++]; > + huff_size[sym] = 0; > + } > + } > + > k = 0; > + code = 0; > for(i=1;i<=16;i++) { > nb = bits_table[i]; > for(j=0;j<nb;j++) { > sym = val_table[k++]; > - huff_size[sym] = i; > - huff_code[sym] = code; > + /* If there are multiple mappings to the same sym (bad files), > keep the first code */ > + if (huff_size[sym] == 0) { > + huff_size[sym] = i; > + huff_code[sym] = code; > + }
do these occur with sym different from 0 ? if its just 0 then this can be simplified alot [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB I do not agree with what you have to say, but I'll defend to the death your right to say it. -- Voltaire
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