[FFmpeg-devel] [PATCH] avformat/img2dec: return immediately in jpeg_probe() when EOI is found

[Carl Eugen Hoyos]

Am Mi., 1. Apr. 2020 um 19:15 Uhr schrieb Matthieu Bouron
<matthieu.bouron at gmail.com>:
>
> On Wed, Apr 01, 2020 at 06:55:42PM +0200, Carl Eugen Hoyos wrote:
> > Am Mi., 1. Apr. 2020 um 18:35 Uhr schrieb Matthieu Bouron
> > <matthieu.bouron at gmail.com>:
> > >
> > > On Wed, Apr 01, 2020 at 06:29:03PM +0200, Carl Eugen Hoyos wrote:
> > > > Am Mi., 1. Apr. 2020 um 18:01 Uhr schrieb Matthieu Bouron
> > > > <matthieu.bouron at gmail.com>:
> > > > >
> > > > > Fixes probing of JPEG files containing MPF metadata appended at the end
> > > > > of the file.
> > > > >
> > > > > The MPF metadata chunk can contains multiple JPEG images (thumbnails)
> > > > > which makes the jpeg_probe fails (return 0) because it finds a SOI
> > > > > marker after EOI.
> > > > > ---
> > > > >
> > > > > This patch fixes probing of JPEG files containing MPF metadata [1] appended
> > > > > at the end of the file.
> > > > >
> > > > > Such files can be produced by GoPro camera (which produces JPEG files
> > > > > with MPF metadata).
> > > > >
> > > > > You can find a sample here:
> > > > > https://0x5c.me/gopro_jpg_mpf_probe_fail
> > > >
> > > > The sample works fine here with FFmpeg 4.2: Is there a regression?
> > >
> > > This sample does not work on FFmpeg 4.2 and master if you set a big
> > > enought formatprobesize (which matches the file size of the sample):
> >
> > Inlined is a patch that fixes detection but I wonder if this shouldn't be
> > detected as mjpeg instead
> >
> > Carl Eugen
> >
> > diff --git a/libavformat/img2dec.c b/libavformat/img2dec.c
> > index 40f3e3d499..4e63b3494e 100644
> > --- a/libavformat/img2dec.c
> > +++ b/libavformat/img2dec.c
> > @@ -737,20 +737,22 @@ static int j2k_probe(const AVProbeData *p)
> >  static int jpeg_probe(const AVProbeData *p)
> >  {
> >      const uint8_t *b = p->buf;
> > -    int i, state = SOI;
> > +    int i, state = SOI, MPF = 0;
> >
> >      if (AV_RB16(b) != 0xFFD8 ||
> >          AV_RB32(b) == 0xFFD8FFF7)
> >      return 0;
> >
> >      b += 2;
> > -    for (i = 0; i < p->buf_size - 3; i++) {
> > +    for (i = 0; i < p->buf_size - 8; i++) {
> >          int c;
> >          if (b[i] != 0xFF)
> >              continue;
> >          c = b[i + 1];
> >          switch (c) {
> >          case SOI:
> > +            if (state == EOI && MPF)
> > +                return AVPROBE_SCORE_EXTENSION + 1;
>
> Your patch might work

You could test it.

> but the code is trying to find JPEG markers in the
> MPF metadata until we reach the first EOI in the MPF JPEG thumbnails,

No, and I am quite sure that I tested this sufficiently.

Shouldn't there be a mpf demuxer that also provides the attachments?

Carl Eugen