[FFmpeg-devel] [PATCH v13] libavcodec/jpeg2000dec.c: Add support for PPT marker

[Gautam Ramakrishnan]

On Mon, Apr 6, 2020 at 5:41 PM Michael Niedermayer
<michael at niedermayer.cc> wrote:
>
> On Mon, Apr 06, 2020 at 09:23:26AM +0530, Gautam Ramakrishnan wrote:
> > On Mon, Apr 6, 2020 at 1:16 AM Michael Niedermayer
> > <michael at niedermayer.cc> wrote:
> > >
> > > On Sun, Apr 05, 2020 at 04:13:28PM +0530, gautamramk at gmail.com wrote:
> > > > From: Gautam Ramakrishnan <gautamramk at gmail.com>
> > > >
> > > > This patch adds functional changes to support the
> > > > PPT marker. This patch fixes bug ticket #4610.
> > > > ---
> > > >  libavcodec/jpeg2000dec.c | 88 +++++++++++++++++++++++++++++++++++-----
> > > >  1 file changed, 77 insertions(+), 11 deletions(-)
> > > >
> > > > diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
> > > > index 732d88e6fc..2af3c61c37 100644
> > > > --- a/libavcodec/jpeg2000dec.c
> > > > +++ b/libavcodec/jpeg2000dec.c
> > > > @@ -83,6 +83,10 @@ typedef struct Jpeg2000Tile {
> > > >      Jpeg2000QuantStyle  qntsty[4];
> > > >      Jpeg2000POC         poc;
> > > >      Jpeg2000TilePart    tile_part[32];
> > > > +    uint8_t             has_ppt;                // whether this tile has a ppt marker
> > > > +    uint8_t             *packed_headers;        // contains packed headers. Used only along with PPT marker
> > > > +    int                 packed_headers_size;    // size in bytes of the packed headers
> > > > +    GetByteContext      packed_headers_stream;  // byte context corresponding to packed headers
> > > >      uint16_t tp_idx;                    // Tile-part index
> > > >      int coord[2][2];                    // border coordinates {{x0, x1}, {y0, y1}}
> > > >  } Jpeg2000Tile;
> > > > @@ -855,6 +859,37 @@ static int get_plt(Jpeg2000DecoderContext *s, int n)
> > > >      return 0;
> > > >  }
> > > >
> > > > +static int get_ppt(Jpeg2000DecoderContext *s, int n)
> > > > +{
> > > > +    Jpeg2000Tile *tile;
> > > > +
> > > > +    if (s->curtileno < 0)
> > > > +        return AVERROR_INVALIDDATA;
> > > > +
> > > > +    tile = &s->tile[s->curtileno];
> > > > +    if (tile->tp_idx != 0) {
> > > > +        av_log(s->avctx, AV_LOG_ERROR,
> > > > +               "PPT marker can occur only on first tile part of a tile.\n");
> > > > +        return AVERROR_INVALIDDATA;
> > > > +    }
> > > > +
> > > > +    tile->has_ppt = 1;  // this tile has a ppt marker
> > > > +    bytestream2_get_byte(&s->g); // Zppt is skipped and not used
> > >
> > >
> > > > +    if (!tile->packed_headers)
> > > > +        tile->packed_headers = av_malloc(n - 3);
> > > > +    else
> > > > +        tile->packed_headers = av_realloc(tile->packed_headers,
> > > > +                                          tile->packed_headers_size + n - 3);
> > >
> > > why is the special case with av_malloc() needed ?
> > >
> > The if else is to check whether this is the first time this tile is being
> > allocated its packed headers. If packed headers does not exist
> > exist, create it. The else condition is just to add a new packed
> > header to it.
>
> what is the problem with
>
> av_realloc(tile->packed_headers,  tile->packed_headers_size + n - 3);
> when tile->packed_headers is NULL and tile->packed_headers_size is 0 for the
> first allocation ?
>
Oh!! Thanks for clearing that out. I did not know realloc could be
used like that.
Was a bit skeptical about writing it that way. I'll test that out and resubmit.
>
> thx
>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> In fact, the RIAA has been known to suggest that students drop out
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-- 
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Gautam |