[FFmpeg-devel] [PATCH]lavf/icodec: Improve probe function

[Carl Eugen Hoyos]

On Tuesday 12 January 2016 02:49:59 pm Michael Niedermayer wrote:
> On Tue, Jan 12, 2016 at 01:49:37PM +0100, Carl Eugen Hoyos wrote:
> > Hi!
> >
> > On Tuesday 12 January 2016 01:33:53 pm Carl Eugen Hoyos wrote:
> > > Attached patch improves ico probing, previously mpeg-2 frames could be
> > > detected.
> >
> > Wikipedia claims that planes can be 0, new patch attached.
> >
> > Carl Eugen
> >
> >  icodec.c |    8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 5587972d12000a679757c9b42947869eb1cee0f5  patchico.diff
> > diff --git a/libavformat/icodec.c b/libavformat/icodec.c
> > index 22e2099..4d6e6dc 100644
>
> tools/probetest 256 4096
> testing size=1
> testing size=2
> testing size=4
> testing size=8
> Failure of ico probing code with score=26 type=1 p=EA6 size=8

Before the old patch, 32 bits were tested and return a value of 25, 
after the patch, 55 bits were tested and returned 26.
Imo, this just shows that probetest cannot see every possible issue.

Improved patch attached.

Carl Eugen
-------------- next part --------------
diff --git a/libavformat/icodec.c b/libavformat/icodec.c
index 22e2099..9cf3dca 100644
--- a/libavformat/icodec.c
+++ b/libavformat/icodec.c
@@ -27,6 +27,7 @@
 #include "libavutil/intreadwrite.h"
 #include "libavcodec/bytestream.h"
 #include "libavcodec/bmp.h"
+#include "libavcodec/png.h"
 #include "avformat.h"
 #include "internal.h"
 
@@ -44,9 +45,30 @@ typedef struct {
 
 static int probe(AVProbeData *p)
 {
-    if (AV_RL16(p->buf) == 0 && AV_RL16(p->buf + 2) == 1 && AV_RL16(p->buf + 4))
-        return AVPROBE_SCORE_MAX / 4;
-    return 0;
+    unsigned i, frames = AV_RL16(p->buf + 4);
+
+    if (AV_RL16(p->buf) || AV_RL16(p->buf + 2) != 1 || !frames)
+        return 0;
+    for (i = 0; i < frames; i++) {
+        unsigned offset;
+        if (AV_RL16(p->buf + 10 + i * 16) & ~1)
+            return FFMIN(i, AVPROBE_SCORE_MAX / 4);
+        if (p->buf[13 + i * 16])
+            return FFMIN(i, AVPROBE_SCORE_MAX / 4);
+        if (AV_RL32(p->buf + 14 + i * 16) < 40)
+            return FFMIN(i, AVPROBE_SCORE_MAX / 4);
+        offset = AV_RL32(p->buf + 18 + i * 16);
+        if (offset < 22)
+            return FFMIN(i, AVPROBE_SCORE_MAX / 4);
+        if (offset + 8 > p->buf_size)
+            return AVPROBE_SCORE_MAX / 4 + FFMIN(i, 1);
+        if (p->buf[offset] != 40 && AV_RB64(p->buf + offset) != PNGSIG)
+            return FFMIN(i, AVPROBE_SCORE_MAX / 4);
+        if (i * 16 + 6 > p->buf_size)
+            return AVPROBE_SCORE_MAX / 4;
+    }
+
+    return AVPROBE_SCORE_MAX / 4 + 1;
 }
 
 static int read_header(AVFormatContext *s)