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

[Carl Eugen Hoyos]

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;
             return 0;
         case SOF0:
         case SOF1:
@@ -775,10 +777,12 @@ static int jpeg_probe(const AVProbeData *p)
                 return 0;
             state = EOI;
             break;
+        case APP2:
+            if (AV_RB24(&b[i + 4]) == AV_RB24("MPF"))
+                MPF = 1;
         case DQT:
         case APP0:
         case APP1:
-        case APP2:
         case APP3:
         case APP4:
         case APP5: